BCM 14.5 middy with VLTOR A5 system. Suggestions?

[jaxman7]

@jerrysimons

Yeah, I have spent many hours pondering how Jaxman and BufordT’s guns run like they do, they definitely seem to be pushing the threshold. Conversely it is rather puzzling that Markm’s 14.5" BCM middy used to run with an H3 buffer new but after a few hundred rounds started to choke with the heavy one (referencing an old thread).

Also, I remember ToddK commenting in one thread that he has run an A5h2 buffer on every configuration Noveske makes without problems. The context was speaking of 14.5" mid-lengths and seemed it indicate Noveske 14.5" mids had bigger gas ports than BCMs 14.5 middy.

Gonna sound like a broken record here man but as I and others have stated before I really do think that friction (or a comparitively lack of it) does make a difference when using a setup w/a short dwell time, weaker ammo, and heavier buffer and being able to reliably shoot. Both my uppers are absolutely butter smooth when racking the charging handle. Tbe smoothest Ive ever felt. There are a few things that can be done to achieve this. Not to mention just plain old shooting/wearing in and other things.

Last weekend. I built a brand new rifle for a guy. Now questionable parts (per his request after my objections) withstanding he-on paper-shouldve had a smooth running rifle.

-14.5" spikes barrel
-nickel boron BCG
-spikes ST2 buffer…weighed by me at 4.1 oz. As opposed to my H2 which is 4.8 oz.
-Brownells carbine spring
-Froglube

Now that sounds like a pretty smooth running setup but compared to my rifles it was WAY more stiff. It would run the Bronze but did NOT like the Tula at all. Given some time and wearing in (giving less friction) I am very curious if it would run the Tula. The track the BC runs along in the upper smoothing out for example may make quite a difference.

-Jax

[jerrysimons]

@jaxman7

Gonna sound like a broken record here man but as I and others have stated before I really do think that friction (or a comparitively lack of it) does make a difference when using a setup w/a short dwell time, weaker ammo, and heavier buffer and being able to reliably shoot.
-Jax

I hear you. I am eager to look into polishing my BCG like you did to your e-carrier. Even still, while you and BufordT are definitely on to something with the friction reduction, it still seems hit or miss on a rifle to rifle basis. The lesson I have gotten is basically just try it and see if it works.

[RMiller]

Had you tried the A5H0 in your setup? Any problems? What size of gas port is your barrel running?

I’m stuck between running the heaviest buffer I can get away with or playing it safe with the lightest buffer I can (A5H0).

@sadmin

14.5 mid with a5h1 here. It was the only config that would consistently work with PMC. 100% bolt lock now. Was it worth it to me in hindsight? No. Car gas with h3 feels the same and is 100% with every flavor. That being said, there is a mondo thread about the 14.5 with LMT enhanced carriers, and that user has no issues.

[Peshawar]

I too have been thinking about putting together an “it’ll eat anything” AR. Been leaning towards the Centurion 14.7 carbine gas barrel. This thread has me thinking about a mid-length gas system, but I’m still not sure. I had previously been under the impression that the carbine length gas was the most accommodating when it comes to digesting all kinds of ammo. Thanks for the info, Gents.

[jaxman7]

@Peshawar

I too have been thinking about putting together an “it’ll eat anything” AR. Been leaning towards the Centurion 14.7 carbine gas barrel. This thread has me thinking about a mid-length gas system, but I’m still not sure. I had previously been under the impression that the carbine length gas was the most accommodating when it comes to digesting all kinds of ammo. Thanks for the info, Gents.

Nothing wrong with that summation man. Many on here would agree.

-Jax

[jerrysimons]

@Peshawar

I too have been thinking about putting together an “it’ll eat anything” AR. Been leaning towards the Centurion 14.7 carbine gas barrel. This thread has me thinking about a mid-length gas system, but I’m still not sure. I had previously been under the impression that the carbine length gas was the most accommodating when it comes to digesting all kinds of ammo. Thanks for the info, Gents.

It is. If you truly want a rifle that will run it all with out thinking twice about it a carbine length gas systemis the way to go.

[BufordTJustice]

It’s not that simple. A middy with a larger gas port would be less sensitive to changes in ammo than a mil-spec (.060-.062 GP) carbine length gun would be. A rifle length gas system would be even less sensitive than a middy (which is why it’s the most forgiving setup).

You want an eat-anything gun? Grab a 16" BCM middy barrel and throw an A5 system under it. Boom. Done. Due to higher port pressures and different pressure curves, properly ported carbines can be MORE finicky than those with middy barrels. Just ask anybody with an LMT 14.5". They shoot nearly as smooth as a middy, and they will promptly tell you to go fuck yourself if you run weak ammo (Tula, PMC, etc.).

16" BCM middy + Vltor A5 will eat damn near anything with NO POLISHING. I’ve seen it. Hell, I have a bud who runs a Tubbs SSS Flatwire spring and carbine H3 buffer under his 16" BCM middy (WAY more spring pressure than the Vltor A5 system) and the damn thing still eats everything he shoves in the chamber…even ultra-weak softball reloads. Don’t over think this.

Jax is 100% correct about friction. You want the smoothest gun possible, do what he and I did. BCM 14.5" middy, LMT E-carrier, Vltor A5 system (with A5H4 buffer), lots of polishing on the carrier, and run that bitch wet. If you are worried about reliability, go with a 16" middy barrel.

[Clint]

@BufordTJustice

It’s not that simple. A middy with a larger gas port would be less sensitive to changes in ammo than a mil-spec (.060-.062 GP) carbine length gun would be. A rifle length gas system would be even less sensitive than a middy (which is why it’s the most forgiving setup).

I think I’m tracking with you.

WHY do you think a middy works with a wider range of ammo?

[1911-A1]

What size are BCM ports?

[BufordTJustice]

@Clint

I think I’m tracking with you.

WHY do you think a middy works with a wider range of ammo?

A) It’s been my experience with the following brands of 16" middies and 16"/14.5" carbine guns: Spikes, BCM (14.5"), Noveske, Daniel Defense, Palmetto State Armory, and Stag. The middy guns, as long as they have a decent sized gas port (all but one DD middy did), were more tolerant of lower powered ammo than their carbine-gas counterparts from the same brand when running the same buffer and spring.

I used to have a spare H3 buffer and Springco Blue spring in my range bag. Every one of the above middies ran Federal M193 55gr and M855 62gr without failure…and so did the carbines.

However, not every carbine that ran with those NATO rounds ran with Tula 55gr (same lot) and PMC 55gr .223 (Bronze IIRC, same lot). The PSA carbine (16"), BCM carbine (14.5"), and DD (14.5") carbine gas guns struggled running the Tula and PMC with some failures to lock back on empty for each and one malfunction (DD; short stroke on PMC…felt like a squib load in the gun’s defense). None of the middies had a bobble. Now, this was not done all at once but just via notes kept over several range trips, but the ammo was consistent and the buffer/spring were identical. It’s less than scientific to be sure.

Also, if I throw an H buffer in a carbine gas gun, I can tell right off the bat whether the gas port is too big within 5 shots when running M193. Using that same buffer, I can’t tell NEARLY as easily when using a middy gas gun (and some def are over-gassed as well).

B) The “WHY”. Well, I’m no engineer, so I would hazard a guess that port pressure plays a a large role, while dwell time could be a factor as well. If we look at the spectrum of guns that are universally recognized as reliable and tolerant of all ammo types and guns that are universally seen as finicky, we see the 20" rifle gas gun at the reliable end and the SBR at the other. They can BOTH be made to work well (don’t get me wrong), but one is a practical sure thing while the other is not. I’m no yoda, but I’ve never seen a properly assembled 20" rifle gas gun fail to function when a parts breakage wasn’t the problem. Even with BADLY worn gas rings. However, I HAVE seen many SBR’s that were properly assembled by Colt certified armorers (and several factory models from LMT, Colt, and Noveske) that had problems functioning 100% using factory ammo. This is purely anecdotal “evidence” (I hesitate to call it that), but it’s what’s been my experience so far.

I’ll also add that the Vltor A5 system seems to have closed the reliability gap quite a bit regarding gas systems and reliability…so it alone has the ability to make my observations moot to a degree. Love me some A5.

Clint, what are your thoughts on the subject. I’d be interested to hear them.

[BufordTJustice]

@1911-A1

What size are BCM ports?

BCM carbine ports are mil spec so the same as Colt (.060-.062/3). I’ve seen several BCM 16" middies with .068 gas ports. My 14.5" middy has a .070 GP best I can guess without taking the FSB off. I know other 14.5" middies have been seen in the wild with .070s.

EDIT: I’ve seen carbines from Bushmaster, Olympic Arms, and DPMFS with gas ports equal to or larger than .070 on 16" carbine gas guns. Those ran like 6.8’s.:rolleyes:

[Iraqgunz]

To the best of my knowledge the TDP calls for .0625-064 for carbine ports and AFAIK that is what BCM is doing.

Mids are in the .076-078 range.

Rifles should be .0935 as far as I know. SPR’s are in the .0995 range.

@1911-A1

What size are BCM ports?

[BufordTJustice]

@Iraqgunz

To the best of my knowledge the TDP calls for .0625-064 for carbine ports and AFAIK that is what BCM is doing.

Mids are in the .076-078 range.

Rifles should be .0935 as far as I know. SPR’s are in the .0995 range.

I stand corrected.

Every Colt i have seen was right near .062. I have heard that BCM had a running change on the 14.5" middy gas port size pretty early in their initial run. Is this true?

Maybe my 14.5 has a .076-078…

Sent from my SPH-D710 using Tapatalk 2

[RMiller]

Thanks everybody.

I got my hands on some additional buffer weights.

This way I can start light, and work my way heavier. (A5H0~A5H1~A5H2)

[RMiller]

Took the new upper out today. Ran the A5H1 first. Locked back 8 out of 10 times on PMC. 100% on Winchester m193.

Swapped out the weights and ran the A5H0. 100% lock back on everything.

Didn’t have any Tula to test. Need to hunt some down.

[vicious_cb]

@Peshawar

I too have been thinking about putting together an “it’ll eat anything” AR. Been leaning towards the Centurion 14.7 carbine gas barrel. This thread has me thinking about a mid-length gas system, but I’m still not sure. I had previously been under the impression that the carbine length gas was the most accommodating when it comes to digesting all kinds of ammo. Thanks for the info, Gents.

Meh, I have a 14.5 middy that will barely run with tula and I mean just barely. Something like it will fail to lock the bolt back half the time doing a single round in the magazine test. Switch to other .223 pressure loads even ones considered weak like Remington UMC and it works perfectly and I am OK with that. Im starting to think maybe its a good thing if a gun barely runs with tula.

[The_Hammer_Man]

I purposely set up the uppers I build for customers so you CAN NOT run Tula through it

Hate what that bi-metal projectile does to barrels. The only reason to buy that stuff is for cheap practice ammo. I’d never use, and neither would most of the people I know, use Tula for anything “serious”.

Considering that most of the PD’s around here are using Winchester ammo it’s probably for the best.

[Peshawar]

@The_Hammer_Man

I purposely set up the uppers I build for customers so you CAN NOT run Tula through it

Hate what that bi-metal projectile does to barrels. The only reason to buy that stuff is for cheap practice ammo. I’d never use, and neither would most of the people I know, use Tula for anything “serious”.

Considering that most of the PD’s around here are using Winchester ammo it’s probably for the best.

Ok, I’ll bite. How exactly do you set up an upper to NOT run bimetal ammunition? And cheap practice ammo, oh… the HORROR.

[The_Hammer_Man]

If you read back a bit you’ll find that gas port size,bolt carrier weight and buffer/spring weight all contribute to a proper cycling weapon.

To make it impossible, or at least difficult, to shoot Tula and it’s variants all you need do is adjust those contributors so that there is enough movement in the system to operate using normal ammunition but not the underpowered ammo.

To test this all you need to do is either increase or decrease your buffer weight OR your buffer spring tension. (IE, switch from a normal buffer spring to a Sprinco blue or red) The loss of function is usually immediate and obvious.

Cheap ammo like UMC/PMC is fine… it uses a copper jacketed bullet. The bi-metal stuff is a copper washed steel bullet. In tests it’s been shown to markedly reduce barrel life.

Now… if you have an endless supply of barrels… use it.

[Peshawar]

@The_Hammer_Man

If you read back a bit you’ll find that gas port size,bolt carrier weight and buffer/spring weight all contribute to a proper cycling weapon.

To make it impossible, or at least difficult, to shoot Tula and it’s variants all you need do is adjust those contributors so that there is enough movement in the system to operate using normal ammunition but not the underpowered ammo.

To test this all you need to do is either increase or decrease your buffer weight OR your buffer spring tension. (IE, switch from a normal buffer spring to a Sprinco blue or red) The loss of function is usually immediate and obvious.

Cheap ammo like UMC/PMC is fine… it uses a copper jacketed bullet. The bi-metal stuff is a copper washed steel bullet. In tests it’s been shown to markedly reduce barrel life.

Now… if you have an endless supply of barrels… use it.

I understand what you mean about the contributing factors, but my question is why you would set a rifle up to NOT perform with a certain type of ammunition intentionally, stacking tolerances on purpose (heavier springs and buffer weights) to prevent reliable operation with lower powered ammo simply out of principle. Would that not also contribute to unreliable operation once the rifle was very dirty, even with normal ammo? It just seems strange to me to want to set the stage for potential problems. Maybe I’m just not understanding something, but I don’t easily see the benefit of doing things that way. The cost of barrels pales in comparison to a large enough stockpile of ammo to wear out said barrels, so it’s far more efficient economically to shoot cheap ammo if you can. That’s why people use 5.45 uppers. Yes, it’s a question of scale, and yes, I wouldn’t shoot bimetal ammo out of a match grade stainless barrel, but if we’re talking chrome lined HF barrels it’s a lot cheaper to shoot out barrels than it is to feed a rifle a strict diet of Lake City. But again, I’m very teachable, and if there’s a reason I’m all ears.