Looking for an apples to apples comparison (ie same muzzle device, ammo, buffer, BCG, springs, etc), along with real world experiences. Just interested in comparing recoil/impulse, so no need to discuss reliability, manuverability, velocity, and overall length issues, etc.
This thread is gonna get ugly.
I have made the exact comparison that you’re requesting. I started w/ a BCM 16" middy upper w/ CAVarms A2 handguards, NiB BCG, FSC556, and a spike’s lower running an H3 buffer and springco RED CS buffer spring. I shot Federal XM193, Tula .223, and BVAC 75gr 5.56.
I then bought a BCM 14.5" middy upper w/ a permed FSC556 and installed the NiB BCG in it. The 14.5" middy on top of the exact same lower, using the exact same ammo, at the same range session felt notably softer. Both to me and a 3-tour Army veteran from Iraq. The BCM 16" is a great gun…and you won’t have an ounce of regret for buying one. BUT, the answer to your question is: the 14.5" shoots softer. The difference is not enormous, but it is present.
I hope to be able to quantify this difference soon. Until then it’s all going to be conjecture and “feel” which is tough to document.
I believe DHart has two virtually identical uppers (or complete rifles) with the only difference being the length of the barrel and in turn the length of the muzzle device (1" on the 16" gun, 1.5" on the 14.5" gun). Might try PMing him, although he seems pretty active here now and may reply on his own.
I made this comparison. I built 2 almost identical rifles. FA carrier, CTR stock, TD grip, Troy EXT rails and sights, T-1’s on Larues, Battlecomps, mid length pencil barrels, etc., etc. The first one has a 16" barrel and 13" rail, the second a 16" cut down to 14.7 and a 11" rail. For full disclosure the 16" gun has a DD barrel and the 14.7" is a BCM barrel. In my rifles the 16’ is a little smoother, no question about it, according to 4 guys at my department and my wife(it’s her gun).
Anyway, I just completed EAG’s 3 day carbine operator course and shot high shooter with the 14.7" gun. I thought I might be handicapping myself by using this lightweight in the course which has many timed courses of fire, but apparantly not. The weight of the rifles without aimpoints was 6lbs. 4 ozs. for the 16" gun and 6lbs 2 ozs. for the 14.7".
I should preface this by stating that I’m an aerospace engineer…
A rough take on the physics @ work here says that the recoil comes from:
a) Powder combustion & accelerating the bullet down the barrel.
b) Thrust from the gasses exiting the barrel.
All things being equal, the shorter barrel gives less time to impart energy to the bullet, which would lead to lower muzzle velocity and less recoil. This also implies higher thrust from the exiting gasses, but I’d bet that the diff. in muzzle energy between the 2 barrels is several times larger than the diff. of thrust of the exhaust gasses.
So if both barrels are about the same weight and shooting the same ammo, the shorter one may have less recoil. But we’re talking about a 9% length difference (1.5"/16) so it’s probably ~ a 9% recoil reduction.
It’s been a few years since I looked up the formula for figuring free recoil but as I recall, the factors were the weight of the rifle, weight of the bullet, weight of the powder charge, muzzle velocity and ejecta (the gases from the burning powder) velocity which is a constant, I believe, of 4750 FPS
I came up with something similar, except that the difference should be the percentage differences between the gas ports and the end of the barrels.
Odds are a lot of the dwell-time pressure difference at the port will be negated by some of the weight difference of the added barrel. The permanent muzzle device or tax stamp should be the point of deciding between those anyway.
How reliable was it with the Sprinco RED spring and H3?
I’m about to use a similar setup. Deciding between a SR-15 build, and a Centurion Arms midlength. (I have spare parts for both guns. Standard bolts, and E3 bolts.)
What? No DELETE option?
Using the Nickel Boron Spike’s BCG (Coated by Fail Zero), the H3 and Springco red ran 100%.
I recently upgrade to a modified all stainless buffer body made by Clint (Slash) at HeavyBuffers.net. It’s a total of 8.3 ounces. I run it in my 14.5" middy w/ a Brownells CS carbine buffer spring. So far, it runs 100% on all the above listed ammunition.
THAT, good sir, is how much the entire system is affected by reducing friction in the BCG. I have a calibrated digital (narcotic) scale and the buffer weighed in at exactly 8.3 ounces. Runs ULTRA smooth. I’m working on creating a new post with a full write-up…and pictures if my wife can ever find the expensive-as-shit sony digital camera i bought for her last christmas. 
8.3 oz. buffer?!
Sounds like no bolt bounce at all. And I think I want one.
How would it run with the Sprinco RED spring?
It didn’t run with the Red spring. 
Only with the true std power Brownells CS buffer spring. BUT, with that spring, it runs EVERYTHING and it has become much more difficult to tell the difference between XM193 and Hornady steel cased ammo or Tula .223. It seems that, as the buffer weight is increased, the difference in bolt group speed between weak ammo and NATO pressure ammo is lessened. I literally loaded every other round with XM193 (Federal) and 55gr Tula .223. I shot 20 rounds that way from a PMAG. Not only were there no malfs, it took some serious concentration to tell which was which toward the end of the mag. I’m not sure what is occurring inside the gun for me to feel this, but I did not notice this with the H3 buffer from G&R, which I also A-B’d during that same range session, using the same ammo. The wife’s shoulder also confirmed my findings…as did an RO who was there.
If only 87GN had this setup in front of his hi-speed camera… :rolleyes:
Either way, this is the softest the gun has EVER shot. I even have some older (read: training only) beater mags that usually failed to lock the bolt to the rear and sometimes failed to feed properly…now they work 100%. Gun still runs just as fast as I can squeeze the trigger. Haha. Like I said, when I stop working like a cat trying to bury a turd on a marble floor, I’ll do my review with pix.
Think it’d run with the blue spring?
I’m about to buy the 8 oz. one from the site. His can be bought with the Wolf XP spring, is that equivalent to the Sprinco RED?
The Spingco Blue spring is not truly std power…it is an uprated spring.
I’d recommend emailing Clint that you’re interested in an XH body w/ three tungsten reciprocating weights inside. That’s what he made for me. He actually, per my request, started me at a 6.5 oz buffer w/ one tungsten and two steel weights (the ‘guts’ of an H buffer). If ur gonna run the spike’s BCG and a spike’s hammer (or will polish the face of your current hammer), and use some slip 2K EWL, the 6.5oz will work 100%. Every gun is different and you’re deep into ‘tinkerer’ territory when you order this buffer. If you get two tungsten and one steel weight, you’ll be right around 7 oz.
I think it’s funny, actually, how these weights appear to mirror the Vltor A5 buffer weights. BUT, the XH body w/ three tungsten weights (8.3oz) is the heaviest AR15 carbine buffer available that actually has the reciprocating weights (which are VITAL to prevent bolt bounce). There are many 9mm buffers with with non-reciprocating weights that will not work well.
As I said, mine is not a stock buffer from Clint. PM me for more questions on this.
It’s listed as a standard item on his site.
I’m using the FailZero carrier, hammer, and charging handle (RTV silicon mod) also, so it should be fine.
http://www.heavybuffers.com/ar15carbine.html
It’s listed as a standard item, by the way.
So the BLUE is stronger than standard power? By how much?
I think I’ll give it a try.
I couldn’t tell you the amount in lbs that the Blue is stronger than the Brownells CS spring, but it feels stronger and the gun wouldn’t cycle with the blue spring.
The buffer I have is not a stock item. The normal heavy buffers only have space for two reciprocating weights. Clint custom machined an XH body to take three reciprocating internal weights. You’d have to email him to get the setup that I have.
Interesting about the super heavy buffer being more consistent with various loads. Wonder why that is.
Do you have any info on the red & blue springs? # of coils & length?
I contacted Springco about the difference and they stated that both springs are the same ‘weight’, but the Red is three coils longer than the blue. The difference in resistance during charging handle manipulation between the two is noticed immediately. It seems the Red + an H3 would be a worthy upgrade for 6.8 uppers.