View Full Version : BCM 11.5 or Geissele Super Duty 11.5
Press Check
02-26-22, 00:29
In the market for another 11.5" upper, and can't make heads or tails of which one to go with. Aside from Geissele costing nearly double, is there any tangible reason to choose one over the other?
Purchased a BCM rifle back in 2011, following all the buzz surrounding the Filthy 14. Rebuilt the upper in 2015 when the KMR system debuted, then again in 2017 when the MCMR system debuted. To date, no problems to speak of with the rifle, and it is boringly reliable.
Purchased a Geissele URGI-I back in 2018 before all the variations happened. Mated to a Colt lower, and on a side note, happens to be the oldest receiver I own, and my most prized. On topic, If I remember correctly, there was a clearance issue with the Daniel Defense gas block, so I returned the upper and asked for their Super Gas Block as the alternative was re-profiling (butchering) the Daniel Defense gas block. Aside from that, no problems to speak of, and their Bomb Proof installation of the gas block was nothing short of impressive.
Point is, familiar with both manufacturers, but can't decide which to go with, so I defer to the good folks of M4C.
I would look at a SOLGW 11.5 with their new M89 Rail. Its a 7075 T6 aluminum rail with a steel barrel nut.
Life time barrel replacement if you shoot it out, Microbest BCG, thermal fit upper, undersized gas block for increased efficiency, correct gas port, and the best anodizing on the market.
If you're shopping specs, it checks all the boxes and then some.
If doesn’t matter. Pick one and shoot the shit out of it.
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If doesn’t matter. Pick one and shoot the shit out of it.
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This should be a pinned post. 100% gospel.
G has 0.068 gas port and a pinned gas block. Smoothest shooter I own.
Aside from Geissele costing nearly double, is there any tangible reason to choose one over the other?
There's NOTHING great enough to justify double the price. Both are nice. (I have only shot the 16" super duty, so overall quality of build is my reference)
Which rail system do you like better?
If you get the BCM with their charging handle and BCG it’s a little over $1K. Not half the price of the G.
The G is ported at .069 vs .076 and the handguard is not an interference fit that requires heat to remove and install.
I had a BCM 11.5” that was very overgassed and showed pressure signs unsuppressed.
I've got the BCM (standard barrel) at just a few dollars over $900 with a charging handle and bolt carrier group. The Geissele is $1200. So you're saving almost $300.
So... Yeah. I'd go BCM. Cost aside, I'd still go BCM. If I could get two, I'd be thrilled to have both. But if I could only have one, it'd be BCM.
I picked up a 14.5" Geissele on their Christmas Sale and it is a really sweet carbine, quality just
reeks in everything they do, saving money is great but lots of people swear buying quality saves
money !
Thoroughbred Arm Co builds some solid uppers to put on their website. Right now they have Colt HRT barreled uppers with URX 4s.
I would look at a SOLGW 11.5 with their new M89 Rail. Its a 7075 T6 aluminum rail with a steel barrel nut.
Life time barrel replacement if you shoot it out, Microbest BCG, thermal fit upper, undersized gas block for increased efficiency, correct gas port, and the best anodizing on the market.
If you're shopping specs, it checks all the boxes and then some.
I have one of these and it is a nice setup. I would recommend taking a look at SOLGW. I was looking into the G Super Duty and SOLGW at the time.
TexasAggie2005
02-26-22, 15:46
There's NOTHING great enough to justify double the price. Both are nice. (I have only shot the 16" super duty, so overall quality of build is my reference)
It's not double, nowhere close. If we try to get apples to apples;
BCM 11.5" complete upper
- $1,016.00
- Mk2 upper receiver
- Mod 3x3 ambi CH
- Mil-spec BCG
- 11.5" hammer forged barrel, gov profile
- reported 0.076" gas port
- set screw gas block
- 10" MCMR handguard
- A2 flash hider
Geissele Super Duty 11.5" complete upper
- $1,200.00
- G super duty keyed upper receiver
- ACH ambi CH
- REBCG w/ forged bolt
- 11.5" hammer forged barrel, G taper profile
- reported 0.069" gas port
- set screw & pinned gas block
- 10.5" Mk16 w/ keyed interlock to upper
- Surefire SOCOM closed tine flash hider
I've got a couple BCMs and though they are both solid rifles, both were overgassed and both the gas block on one and the FSB on the other were too hard to remove in order to mitigate the overgassing. If it were my money, there's no doubt in my mind I'd go with the Geissele: better BCG and forged bolt, better gas block installation, correctly gassed, better handguard, better muzzle device, better reputation for accuracy, better fit 'n finish.
Press Check
02-26-22, 16:37
I should have mentioned that I already have a spare BCM BCG in Ionbond, and one of the older Charging Handles.
No data regarding how much the Geissele 11.5 weighs. Anyone know?
Serious Account
02-26-22, 20:20
Geissele without any question.
Going by the gas port size alone the Geissele is clearly the superior choice. Geissele 11" has the proper/optimum gas port size (.068), whereas the BCM is severely overgassed. Geissele also has superior/more robust handguard and barrel, better BCG etc..
I thought the suggested price difference was way out of line, and it does seem to be. For an extra ~$200, I also suggest Geissele if it will be used for serious purposes. Their rails are damn stout without being overly heavy. Their bomb-proof gas block installation is a definite improvement over set screws. The gas port size is also more appropriate.
If it'll just be a range gun, then get whatever you can, they should both run well.
BCM is good; Geissele is better for reasons stated, and if the prices posted above are accurate (keep in mind they could vary due to sales, availability, etc.), it's really a no-brainer.
-Rainman
Id go SOLGW or Colt. BCM an Geiselle (DD) are over gassed. If your dead set then thats what it is.
Id go SOLGW or Colt. BCM an Geiselle (DD) are over gassed. If your dead set then thats what it is.
The Geisselle has a smaller gas port than the SOLGW. G-.068 vs S-.070
Press Check
02-27-22, 09:21
Thanks for all the feedback so far.
I’m definitely familiar with gas port sizes, but all of my experience has been exclusive to barrels with oversized gas ports. I.E., Colt, BCM, Daniel Defense, etc.
Having had no experience with a properly sized gas port, is it vastly different than an overgassed rifle? Also, when referencing port sizes, is it about a softer shooting rifle, or a rifle that’s not needlessly beating up the internal components?
Thanks for all the feedback so far.
I’m definitely familiar with gas port sizes, but all of my experience has been exclusive to barrels with oversized gas ports. I.E., Colt, BCM, Daniel Defense, etc.
Having had no experience with a properly sized gas port, is it vastly different than an overgassed rifle? Also, when referencing port sizes, is it about a softer shooting rifle, or a rifle that’s not needlessly beating up the internal components?
Colts have correct gas ports and DD reduced their gas ports a few years back.
Over gassed guns will cycle cheaper lower pressure ammo at the expense of increased parts wear and recoil.
Serious Account
02-27-22, 10:05
Smaller/proper gas port size (Geissele) doesn't just mean softer shooting; with Geissele 11" you also get reliable/optimum function, longer parts lifespan (less wear and tear on the gun especially when using 556 ammo) and last but not least: a gun that is MUCH more suppressor friendly (if you ever plan on suppressing your AR). Gas port size absolutely needs to be taken into consideration when selecting/purchasing an AR because it's literally the foundation of how a gun would perform. All in all Geissele really look and feel like a gun that is build for duty/combat.
It's your choice at the end of the day of course. I personally wouldn't even consider a BCM (again their 11" is stupidity overgassed). I'd just Geissele and be glad.
Can you quantify those statements or are your regurgitating something you’ve read?
This site is largely about nuance, but statements need to be qualified and quantified whenever possible.
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Can you quantify those statements or are your regurgitating something you’ve read?
This site is largely about nuance, but statements need to be qualified and quantified whenever possible.
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Are you familiar with the over gassed MK18? I think it had something like a .080-.082 gas port and then DD reduced it to .069 - .070
Are you familiar with the over gassed MK18? I think it had something like a .080-.082 gas port and then DD reduced it to .069 - .070
Absolutely. This isn’t that drastic of a difference, nor is it really relevant in a meaningful way.
Sometimes it sounds like the YouTube “reviewers” going on about trigger reset or some other such nonsense that really doesn’t affect anything in the real world. Quit mentally masturbating and go shoot the gun.
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Absolutely. This isn’t that drastic of a difference, nor is it really relevant in a meaningful way.
Sometimes it sounds like the YouTube “reviewers” going on about trigger reset or some other such nonsense that really doesn’t affect anything in the real world. Quit mentally masturbating and go shoot the gun.
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It is absolutely a drastic difference.
What is over gassing? It is when the bolt is unlocked prematurely when the barrel pressures are still relatively high. It can be caused by a few things but the biggest cause is a gas port that is over sized. The industry embraced the idea that a over gassed gun is a reliable gun. But thats not the case. When the industry began to realize this they introduce heavy weight buffers to mend the problems of their over gassed guns.
When an AR is over gassed the bolt speed increases and this can cause rounds to not be picked up or the bolt not locking back on an empty magazine. It can also effect how well the gun ejects the spent rounds. This causes problems with reliability.
An over gassed gun can also reduce the velocity because the bolt is unlocking while there is still more pressures in the barrel. Those additional pressures are used to vercome the resistance of the bullet and increase velocity. Once a bullet is moving is doesn't take much to keep it moving so any amount of gas bleed off by a over gassed system can reduce velocity.
Another problem is premature wear on the locking lugs. When a gun is properly gassed the amount of pressure on the locking lugs is minimal compared to a gun that is over gassed.
And finally, having a properly gassed gun will reduce the felt recoil. When a gun is over gassed the bolt unlocks earlier than is should when the pressures and gas volume are still higher than they should be. The additional pressures and volume exert more force upon the bolt and buffer. When this happens it increases their speed as they travel rearward those fast moving bolt and buffer come to an abrupt stop as they impact the rear of the buffer tube very hard.
Are you familiar with the over gassed MK18? I think it had something like a .080-.082 gas port and then DD reduced it to .069 - .070
Yeah but what’s your point? You’re just looking for an example of a grossly over gassed gun?
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If you get the BCM with their charging handle and BCG it’s a little over $1K. Not half the price of the G.
The G is ported at .069 vs .076 and the handguard is not an interference fit that requires heat to remove and install.
I had a BCM 11.5” that was very overgassed and showed pressure signs unsuppressed.
This was my first thought as well, double the price vs what you get on each unit. I am a huge BCM fan, but it isn't half/double. The sale last week had some very reasonable upper prices on G's website. Almost bit me again.
Back when you could get a KAC SR15 for $2,300 or less which I did and people said they are double the price. Nope, add a SSA trigger, hand guard ....and your base gun gets close or over $2k. I always thought it and now the G rifles are a deal.
PB
Serious Account
02-27-22, 20:38
Can you quantify those statements or are your regurgitating something you’ve read?
This site is largely about nuance, but statements need to be qualified and quantified whenever possible.
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What? Everything I've said in my previous comment are verifiable facts.
.068 vs .076 is a significant difference in term of gas drive and dwell time.
This will effect long term parts lifespan, suppressor usage etc... Geisselee has got the gas port right; BCM overgassed the shit out of their gun.
It's important for buyer to know the difference.
It is absolutely a drastic difference.
What is over gassing? It is when the bolt is unlocked prematurely when the barrel pressures are still relatively high. It can be caused by a few things but the biggest cause is a gas port that is over sized. The industry embraced the idea that a over gassed gun is a reliable gun. But thats not the case. When the industry began to realize this they introduce heavy weight buffers to mend the problems of their over gassed guns.
When an AR is over gassed the bolt speed increases and this can cause rounds to not be picked up or the bolt not locking back on an empty magazine. It can also effect how well the gun ejects the spent rounds. This causes problems with reliability.
An over gassed gun can also reduce the velocity because the bolt is unlocking while there is still more pressures in the barrel. Those additional pressures are used to vercome the resistance of the bullet and increase velocity. Once a bullet is moving is doesn't take much to keep it moving so any amount of gas bleed off by a over gassed system can reduce velocity.
Another problem is premature wear on the locking lugs. When a gun is properly gassed the amount of pressure on the locking lugs is minimal compared to a gun that is over gassed.
And finally, having a properly gassed gun will reduce the felt recoil. When a gun is over gassed the bolt unlocks earlier than is should when the pressures and gas volume are still higher than they should be. The additional pressures and volume exert more force upon the bolt and buffer. When this happens it increases their speed as they travel rearward those fast moving bolt and buffer come to an abrupt stop as they impact the rear of the buffer tube very hard.
No, the difference between the 11.5 BCM and the 11.5 Geissele are not a drastic difference, especially not as your hyperbolic example. I stopped right here. I don’t need a lecture on theory. The practical difference doesn’t matter. Shoot the damn gun.
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What? Everything I've said in my previous comment are verifiable facts.
.068 vs .076 is a significant difference in term of gas drive and dwell time.
This will effect long term parts lifespan, suppressor usage etc... Geisselee has got the gas port right; BCM overgassed the shit out of their gun.
It's important for buyer to know the difference.
Saying vaguely “will affect long term parts lifespan”. You’ve got to say specifics. No vague statements. There is no practical difference between the 11.5 Geissele and the 11.5 BCM.
In a practical way, there is no significant difference. Just shoot the damn gun and stop worrying if that bolt lug is going to last 16,000 or 14,000 rounds.
Why can hypothetical the shit out of this.
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https://docs.google.com/spreadsheets/d/1tXunBDX5Gaz87BqxwNxDUlWNK9nEv-cZEQoLq2JXXrk/edit#gid=766121382
According to this doc, Colt 11.5" gas ports seem to be around .074" while recent years production BCMs seem to be around .073-.074. So how is it overgassed? Seeing as Colt's 11.5" is literally mil-spec and the original gas port for 11.5" ARs, how can BCM's be overgassed? It seems to be right up in there with Colt, at least with more recent years' production.
If anything I'd be concerned about the Geiselle being undergassed under certain conditions like severe cold or otherwise hostile conditions. Sure it's nice to have an AR that shoots as smooth as possible on a sunny warm day at the range, but for combat use there's a reason they don't gas it to barely be enough to cycle reliably under ideal conditions.
I’d say a significant difference, other than the gas port size, which for someone like me who only shoots suppressed is crucial: is the fact that there is zero upgrading needed to the G gun. By the time, you bring the BCM up to G spec, in terms of together and controls, you’re adding another few hundred, if you want to ignore the gas port and go apples to apples.
Just a thought.
No, the difference between the 11.5 BCM and the 11.5 Geissele are not a drastic difference, especially not as your hyperbolic example. I stopped right here. I don’t need a lecture on theory. The practical difference doesn’t matter. Shoot the damn gun.
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The drastic difference is between .070 and .080
This is why you go shoot your shit. If ain’t gonna matter people.
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https://docs.google.com/spreadsheets/d/1tXunBDX5Gaz87BqxwNxDUlWNK9nEv-cZEQoLq2JXXrk/edit#gid=766121382
According to this doc, Colt 11.5" gas ports seem to be around .074" while recent years production BCMs seem to be around .073-.074. So how is it overgassed? Seeing as Colt's 11.5" is literally mil-spec and the original gas port for 11.5" ARs, how can BCM's be overgassed? It seems to be right up in there with Colt, at least with more recent years' production.
If anything I'd be concerned about the Geiselle being undergassed under certain conditions like severe cold or otherwise hostile conditions. Sure it's nice to have an AR that shoots as smooth as possible on a sunny warm day at the range, but for combat use there's a reason they don't gas it to barely be enough to cycle reliably under ideal conditions.
I was confused on this very issue last year when working on a coworkers BCM 11.5”.
I had built a couple of FBI clones for a guy a couple of years ago and measured the ports on those heavy 11.5” at .069”. I assumed, incorrectly, that all Colt 11.5”a were ported the same.
I don’t know if my coworker had other issues, but his BCM 11.5” flattened primers, had ejector swipe that shaved brass, and dented the side of cases with ammo that showed none of those signs from the barrel I replaced it with, a Colt 11.5” with the same .074” port as the BCM.
I don’t know if my coworker had other issues, but his BCM 11.5” flattened primers, had ejector swipe that shaved brass, and dented the side of cases with ammo that showed none of those signs from the barrel I replaced it with, a Colt 11.5” with the same .074” port as the BCM.
Yeah.. that would have nothing to do with port size. But it could be a tight bore or a short leade. Do you know if it was a hammer forge or button rifle?
Yeah.. that would have nothing to do with port size. But it could be a tight bore or a short leade. Do you know if it was a hammer forge or button rifle?
I don’t know.
I don’t know.
Gotcha. Button rifling can produce an occasional bad barrel. Would have been interesting to pin gauge the bore or run Ned's reamer.
Yeah. I didn’t have any gages and he had already bought the new barrel so we test fired it and went along our way.
I had the exact same issue with a 16” M4 profile BCM that I corrected with a Colt 6920 takeoff.
I’m kinda gunshy on barrels that aren’t Colt anymore.
I know Paul at BCM takes quality seriously. Iraqgunz worked there for a bit, and Paul had given him some barrels to use in his armorer course that they quit using because the quality wasn't up to snuff.
I know Paul at BCM takes quality seriously. Iraqgunz worked there for a bit, and Paul had given him some barrels to use in his armorer course that they quit using because the quality wasn't up to snuff.
What was wrong with them?
Other than unremarkable accuracy but still within mil spec, I find it hard to believe that BCM barrels lead to reliability/durability problems outside of the occasional freak lemon.
It's been said, but to reiterate:
BCM 11.5" is way over-gassed, especially with can. The Colt is as well, but not as bad.
Get the G.
It's been said, but to reiterate:
BCM 11.5" is way over-gassed, especially with can. The Colt is as well, but not as bad.
Get the G.
According to the google doc in the previous page, it looks like multiple examples of recent years production of BCM 11.5" barrels are gassed virtually identically to Colt 11.5" barrels. I don't see how Colt barrels are overgassed when they are the baseline, original standard and developed the gas port dimensions decades ago. I guess it is overgassed if you use a suppressor, but anything that's perfectly gassed for a can is going to be undergassed during non-suppressed use. It may only show itself under certain conditions, but still.
It seems like many people now think any gassing over the point where it is just barely getting enough gas to make the bolt lock back on an empty mag in ideal range conditions is overgassed, not considering that these are combat weapons meant to be reliable under a wide variety of circumstances and adverse conditions in climates all over the world. For a range toy or race gun that needs to shoot as flat and smooth as possible, I guess it doesn't matter, but for anything serious it does.
Mk18 runs with a .070 port on a 10.3” barrel. If a 11.5” can’t run with that port size, I’d throw it in the fire pit.
According to the google doc in the previous page, it looks like multiple examples of recent years production of BCM 11.5" barrels are gassed virtually identically to Colt 11.5" barrels. I don't see how Colt barrels are overgassed when they are the baseline, original standard and developed the gas port dimensions decades ago. I guess it is overgassed if you use a suppressor, but anything that's perfectly gassed for a can is going to be undergassed during non-suppressed use. It may only show itself under certain conditions, but still.
It seems like many people now think any gassing over the point where it is just barely getting enough gas to make the bolt lock back on an empty mag in ideal range conditions is overgassed, not considering that these are combat weapons meant to be reliable under a wide variety of circumstances and adverse conditions in climates all over the world. For a range toy or race gun that needs to shoot as flat and smooth as possible, I guess it doesn't matter, but for anything serious it does.
If Crane spec for a 10.3" is 0.070", then an 11.5" would need to be SMALLER.
The 0.074" is too big, especially suppressed IMO.
Colt's 6933 barrel is not the same as their HRT barrel.
11.5" with GP ~0.065" run great with and without can even when dirty as f*ck in my experience. Not saying this will work for everyone in every situation. You need to factor in all variables (ammo, buffers, springs, BCG, environment), and test it.
You do you, homie.
Mk18 runs with a .070 port on a 10.3” barrel. If a 11.5” can’t run with that port size, I’d throw it in the fire pit.
Yup.
All an 11.5 needs is 0.068.
My 11.5 Geissele locks back with steel unsuppressed.
Having said that, I run M193 suppressed almost exclusively, but I run a steel function test because I know if it’ll run that, it’ll run anything.
What was wrong with them?
Other than unremarkable accuracy but still within mil spec, I find it hard to believe that BCM barrels lead to reliability/durability problems outside of the occasional freak lemon.
These were not BCM barrels. This was early on before BCM only sold their own to keep the quality up.
Serious Account
03-01-22, 07:31
Saying vaguely “will affect long term parts lifespan”. You’ve got to say specifics. No vague statements. There is no practical difference between the 11.5 Geissele and the 11.5 BCM.
In a practical way, there is no significant difference. Just shoot the damn gun and stop worrying if that bolt lug is going to last 16,000 or 14,000 rounds.
Why can hypothetical the shit out of this.
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That isn't a vague statement though. Port size DOES have an effect on not only function but longevity. It's critical that the port size is as optimum as possible.
Serious Account
03-01-22, 07:32
and BTW where are you guys seeing these .074 11" Colt barrels from? Are you sure they aren't some random "home made" guns with mis-matching of parts?
Every single Colt 11" I have examine and handle have been .069
FYI: New BCM 11.5" BFH barrels GP measure .070. A change from their previous .076 spec.
FYI: New BCM 11.5" BFH barrels GP measure .070. A change from their previous .076 spec.
First time I’ve heard that, where’d you get that from?
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and BTW where are you guys seeing these .074 11" Colt barrels from? Are you sure they aren't some random "home made" guns with mis-matching of parts?
Every single Colt 11" I have examine and handle have been .069
The heavy FBI barrels are .069”, the 6933 are .074”.
That isn't a vague statement though. Port size DOES have an effect on not only function but longevity. It's critical that the port size is as optimum as possible.
Again, no specifics.
Go shoot the gun. It doesn’t matter. The gun isn’t going to fall apart. It isn’t going to get you killed.
Go shoot the damn gun. Skills trump four or five thousandths in gas port diameter.
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Again, no specifics.
Go shoot the gun. It doesn’t matter. The gun isn’t going to fall apart. It isn’t going to get you killed.
Go shoot the damn gun. Skills trump four or five hundredths in gas port diameter.
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While I agree with you, shooting and having a properly made gun aren’t mutually exclusive. You can buy whichever gun you perceive to best fit your needs, and also shoot the %#$& out of it. And 6 thousandths certainly can make a significant difference in perceived recoil (dot movement) and the rate of filth buildup. However, I don’t know if it does in the barrels being debated here. Between the two, I only have experience with the G 11.5”s, and they’ve been good. They run like they’re made to be part-time suppressed.
But the EZ Tune now makes it easy (for a price) to correct something as simple as a port designed for internet people that insist on upgrading their buffer and spring and then bitching if it won’t eat Tula 55. So yeah, a .070” ish port is best, and I’d rather all the makers do that, but no sweat if either barrel turns out to have a .076” blowhole.
Again, no specifics.
Go shoot the gun. It doesn’t matter. The gun isn’t going to fall apart. It isn’t going to get you killed.
Go shoot the damn gun. Skills trump four or five hundredths in gas port diameter.
My first SBR had a gargantuan port. It was so miserable to shoot, I just did not shoot it. This turd had so much bolt speed, it would outrun the bolt catch. This was 25 plus years back before we had options.
I don't believe poorly spec'd ports will damage a gun, but I DAMNED sure like shooting a correctly gassed gun much more.
My first SBR had a gargantuan port. It was so miserable to shoot, I just did not shoot it. This turd had so much bolt speed, it would outrun the bolt catch. This was 25 plus years back before we had options.
I don't believe poorly spec'd ports will damage a gun, but I DAMNED sure like shooting a correctly gassed gun much more.
Yeah but that’s not what we are talking about here. We are talking about a minor difference between these two.
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Yeah but that’s not what we are talking about here. We are talking about a minor difference between these two.
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Is it though? Seriously, i’m not sure because my 11.5” experience is with ones that have standard 0.070” ish ports, and I don’t even know if the BCM port is really 0.076”. The one on my 12.5” BCM was large enough that I choked it down significantly even without the can.
Just looking at the numbers being discussed (.070” vs .076”) we’re talking about a difference in port sizes approaching that of the Mk18 vs M4, which are on opposite extremes of barrel length on the same gas system length. If we added that much port diameter to a 6920, we’d probably be mortaring it with M855. I doubt BCM is making a gun quite that shitty though.
I’ve got like a dozen different sizes EZ Tune tubes, and experimenting with them has led me to beleive that seemingly small numerical changes like 6 thou can be quite noticeable. Additionally, even .070 is more than a 11.5” needs, although I’d say its just fine, since it runs relatively light .223 just fine.
seemingly small numerical changes like 6 thou can be quite noticeable. Additionally, even .070 is more than a 11.5” needs, although I’d say its just fine, since it runs relatively light .223 just fine.
Totally agree on both points. .006" can be a big difference. Although I have an older 11.5 BCM barrel that I can't tell you (without measuring) what the port might be. It runs fine... no indication of over gassing.
My .070" 11.5 is indeed where that port size belongs. Runs well on 5.56 and .223 pressure.
Yeah but that’s not what we are talking about here. We are talking about a minor difference between these two.
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It's not a minor difference. I'm guessing you've never run a BCM 11.5" with a can? It's whack compared to a properly sized GP.
It was said earlier, 0.068 then later 0.069 vs 0.076, then somebody corrected them saying 0.070 is where BCMs are now.
I’ve got or have had everything from old BCM 11.5s, new BCM 11.5s old MK18 uppers and even Hodge 12.5s. Hell, I think one of the ones we used to bear up on was a 6920 barrel cut down. Outside of the 6920 barrel, no reliability issues, no guns magically breaking, and none had recoil that broke my shoulder. None were unusable. None of them failed with a Surefire SOCOM.
To believe people online, there’s no way that somebody could survive a real fight with an MK18 because it would be too dirty to function a half
magazine in and would break if you got past that.
We can all get to invested in nuance here. I have a buddy without a rifle for three years now, because he wants to “buy once cry once” with the most cutting edge, softest shooting piece space magic rifle ever. Nothing else will do, you know. When push comes to shove, I would have to rely on my buddy that owns (and regularly trains with) a RRA for the last several years.
OP should pick which one he likes and shoot the shit out of it and all will be A-ok.
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It's not a minor difference. I'm guessing you've never run a BCM 11.5" with a can? It's whack compared to a properly sized GP.
I do it about once a month, Scooter.
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Serious Account
03-01-22, 12:41
The facts and data/experiences are all there, and yet we still have folks in denial clinging onto this false notion of "there's no difference! just shoot your gun!" You have all the right to buy barrel with blowhole size port if that what you prefer, but saying there's "little or no difference" is just flat out false/dishonest.
FYI Geissele 11" even comes with H3 buffer and yet eat everything reliably (suppressed and unsuppressed)
The facts and data/experiences are all there, and yet we still have folks in denial clinging onto this false notion of "there's no difference! just shoot your gun!" You have all the right to buy barrel with blowhole size port if that what you prefer, but saying there's "little or no difference" is just flat out false/dishonest.
FYI Geissele 11" even comes with H3 buffer and yet eat everything reliably (suppressed and unsuppressed)
I didn’t say there is no difference. You failed to qualify a difference.
Saying “it’s cleaner” is not quantified.
Saying “it shoots so much smoother!” is not quantified.
Saying “it lasts longer!” is not quantified.
Stop the bullshitting. I know it hurts the feels to be challenged, but backhanded attempts at snark and personal attack don’t change the fact that you’ve poorly defended your position with speculation and vague statements of superiority. Data and science matter much more than speculation.
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Since we don't know for certain what size gas port the BCM actually has, this has been a mostly pointless argument.
I just sent them an e-mail asking for the port size. It took about 30 seconds.
Serious Account
03-01-22, 13:07
I didn’t say there is no difference. You failed to qualify a difference.
Saying “it’s cleaner” is not quantified.
Saying “it shoots so much smoother!” is not quantified.
Saying “it lasts longer!” is not quantified.
Stop the bullshitting. I know it hurts the feels to be challenged, but backhanded attempts at snark and personal attack don’t change the fact that you’ve poorly defended your position with speculation and vague statements of superiority. Data and science matter much more than speculation.
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That's some hilarious strawman you just spew there (after gotten corrected). But whatever you do you. Good luck.
That's some hilarious strawman you just spew there (after gotten corrected). But whatever you do you. Good luck.
Basically what I figured you’d say. I don’t need your luck, I shoot my rifles.
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Serious Account
03-01-22, 13:20
On a side note to this topic: Daniel Defense 11.5" used to have .076 port; but now all CURRENT DD 11.5" have .069 port size.
More and more credible AR-15 manufacturers are starting to realize that their SBR are over-gassed to hell and thus now reducing their port size for optimum performance (with and without suppressor, and in all conditions)
If BCM is smart then they better follow suit.
No one here has the instrumentation to meter the energy of the recoil on an over-gassed gun or measure the bolt speed. But Helen Keller can tell the difference between the two.
Not having the equipment to quantify it doesn't make it untrue.
Mark, we do have the ability, outside of “feels” to do things like provide quantifiable data points.
And sometimes we do have instrumentation such as shot timers, chronographs, etc. I mean it would be easy to verify the *significant* velocity lost to the alleged over-gassed 11.5” BCM. Claims like that are easy to test and verify.
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It was said earlier, 0.068 then later 0.069 vs 0.076, then somebody corrected them saying 0.070 is where BCMs are now.
I’ve got or have had everything from old BCM 11.5s, new BCM 11.5s old MK18 uppers and even Hodge 12.5s. Hell, I think one of the ones we used to bear up on was a 6920 barrel cut down. Outside of the 6920 barrel, no reliability issues, no guns magically breaking, and none had recoil that broke my shoulder. None were unusable. None of them failed with a Surefire SOCOM.
To believe people online, there’s no way that somebody could survive a real fight with an MK18 because it would be too dirty to function a half
magazine in and would break if you got past that.
We can all get to invested in nuance here. I have a buddy without a rifle for three years now, because he wants to “buy once cry once” with the most cutting edge, softest shooting piece space magic rifle ever. Nothing else will do, you know. When push comes to shove, I would have to rely on my buddy that owns (and regularly trains with) a RRA for the last several years.
OP should pick which one he likes and shoot the shit out of it and all will be A-ok.
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Since we don't know for certain what size gas port the BCM actually has, this has been a mostly pointless argument.
I just sent them an e-mail asking for the port size. It took about 30 seconds.
I mostly agree with the above, however as far as I can tell, I’m the only one to bring up Mk18s prior to Mrad, and it was an example of a gas port size that works, thus would be fine, and is fine in 11.5” guns. And they can go smaller and be fine, as well, with proper ammo.
Unless you mean commercial “Mk18”s.
Mark, we do have the ability, outside of “feels” to do things like provide quantifiable data points.
And sometimes we do have instrumentation such as shot timers, chronographs, etc. I mean it would be easy to verify the *significant* velocity lost to the alleged over-gassed 11.5” BCM. Claims like that are easy to test and verify.
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I’d be surprised if gas port sizes within any reasonable range would affect velocity in a way that was significant, given that one barrel to the next will show variation in velocity, as will the ammo (obviously).
If anyone knows where I could find data for that, I’d be one hard nerd.
Edit: I just thought about this more, and realized that the fastest 14.5” I’ve ever owned also has the largest port.
Small differences in port size make a surprisingly large difference in Gas Drive.
The flow rate changes with the area, which is the square of the diameter difference.
For example, an 076 port has 25% more area / gas drive than an 068 port.
ETA pic for interest
https://d2j6dbq0eux0bg.cloudfront.net/images/812059/1643003206.jpg
I mostly agree with the above, however as far as I can tell, I’m the only one to bring up Mk18s prior to Mrad, and it was an example of a gas port size that works, thus would be fine, and is fine in 11.5” guns. And they can go smaller and be fine, as well, with proper ammo.
Unless you mean commercial “Mk18”s.
I’d be surprised if gas port sizes within any reasonable range would affect velocity in a way that was significant, given that one barrel to the next will show variation in velocity, as will the ammo (obviously).
If anyone knows where I could find data for that, I’d be one hard nerd.
Edit: I just thought about this more, and realized that the fastest 14.5” I’ve ever owned also has the largest port.
Yeah the last point was silly when the guy made it and it isn’t hard to measure. That’s why I’m saying make the claim, we need something to very fit. I have measured velocity on my guns and don’t find the gassy ones to be slower at all.
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I received an answer back from BCM regarding the current gas port size of their 11.5" CQB 11 MCMR.
They consider gas port sizes proprietary information and are not published.....even though an owner of said barrel can remove the gas block, measure the port, and publish the info themselves.
I don't recall anyone suggesting that the BCM is a better purchase at roughly $200 less, so I'd say this question has been answered.
They consider gas port sizes proprietary information and are not published.
I consider this a huge turnoff. If I’m ordering a pickup truck and I ask what size tires come on it, I’ll get an answer. If I’m asking about twist rate, I’ll get an answer. If I ask what fuel a generator uses, or how many calories in a meal, or or the mass of a kettlebell, I’ll get an answer.
Why is the gun industry shitty by default? Like… I can just not buy that product and buy a Hodge 12.5” instead from a company like FCD that puts the gas port size in the description. The fact that companies believe I’m too stupid to have access to that info tells me that they designed it to run weak ammo, and thats all I need to know.
I absolutely love the BCM that I bought secondhand, but I don’t see myself buying any more, with that response. They make a huge deal of posting all kind of nerd stuff on the description pages for their barrels… why is a drill bit size “proprietary”? What’s proprietary next? Bore diameter?
The fact that companies believe I’m too stupid to have access to that info tells me that they designed it to run weak ammo, and thats all I need to know.
I think this is exactly the case. As companies grow they have a choice and sometimes they tailor more to the lowest common denominator. I am actually super surprised that DD changed the port spec on the MK18 for the civilian side a while back. Good on them and if it doesn't shoot your crappy ammo unsuppressed buy some better ammo or get a different barrel. They would rather have the customers that know what they want then the lowest common denominator. That being said DD gathered more data through testing, more people started shooting suppressed, and their clientele wanted the same gun that the military was getting. But they are far more transparent about these things than BCM.
Serious Account
03-01-22, 16:51
DD, Geissele, SOLGW are all very open about their rifles' port size (and noticed how these companies have optimum or at least close to optimum gas port size) . Tell me all I need to know about the quality and confidence they have in their products.
Since we discussed earlier in this thread chamber size, and a few posts ago we discussed measuring shit…
I pulled my BCM Kino out of the safe, along with 3 other barrels/guns at random. I cleaned the chambers and barrels with brushes, snakes, mops and CLP. I checked their chambers with a Michiguns 556? Gauge.
Barrel brand: pass/fail
BCM: pass
BRT: pass
Noveske: fail (its a “5.56 Match Mod 0”, like a Wylde chamber, so this was expected, and normal, and should not reflect negatively on the company or their marketing)
BA Hanson: pass
I don’t own a G upper.
Nightstalker865
03-01-22, 17:12
I consider this a huge turnoff. If I’m ordering a pickup truck and I ask what size tires come on it, I’ll get an answer. If I’m asking about twist rate, I’ll get an answer. If I ask what fuel a generator uses, or how many calories in a meal, or or the mass of a kettlebell, I’ll get an answer.
Why is the gun industry shitty by default? Like… I can just not buy that product and buy a Hodge 12.5” instead from a company like FCD that puts the gas port size in the description. The fact that companies believe I’m too stupid to have access to that info tells me that they designed it to run weak ammo, and thats all I need to know.
I absolutely love the BCM that I bought secondhand, but I don’t see myself buying any more, with that response. They make a huge deal of posting all kind of nerd stuff on the description pages for their barrels… why is a drill bit size “proprietary”? What’s proprietary next? Bore diameter?
I completely agree with you. BCM builds a great product, but they seem to have stopped innovating/evolving over the last few years. Nowadays I don’t think I would buy another one. Just too many other great options on the market.
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I
They consider gas port sizes proprietary information and are not published.....even though an owner of said barrel can remove the gas block, measure the port, and publish the info.
If they won’t tell me the port size I automatically classify it as dirt shooter tier and I’ve never passed up a good barrel with that method. :laugh:
First time I’ve heard that, where’d you get that from?
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Measured From both barrels I purchased 2 months ago..........easy
DD, Geissele, SOLGW are all very open about their rifles' port size (and noticed how these companies have optimum or at least close to optimum gas port size) . Tell me all I need to know about the quality and confidence they have in their products.
SOLGW advertise their gas ports but last I checked, they are not conservative. In fact I believe they’re right we’re BCMs are rumored to be. The difference is that when you ask them, they’ll proudly state it and say it’s because they make fighting guns that are designed to function in sub-optimal conditions above all else.
Measured From both barrels I purchased 2 months ago..........easy
Nice, thanks.
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