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Posted: 10/17/2013 10:17:05 PM EDT
| Ok guys, I'm sure this horse has been beaten into a bloody pulp, but I have a few questions about buffer selection for one of my new builds. The build in question is a 14.5" BCM mid length on a ST lower. I plan on running a Tubbs CS flatwire buffer spring and either a ST-T2 buffer or Vltor A5 system. BCG will be a FA BCM, Spikes or Fail Zero (have all 3, just haven't decided which one to use. Anyone running a similar setup and if so could you shed some light on the subject for me in terms of function, reliability, ammo issues etc.? Any input would be greatly appreciated. |
| Thanks guys. I've ran H and H2 buffers in my carbine length gas systems for years. This is my first middy build, so just trying to figure out what works best. Not sure the Vltor A5 is worth the $$, but some do speak highly of the setup. I'll probably end up playing around with the weights in my buffer until I find the right setup. I don't shoot Tula or Wolf, but who knows what the future will bring as far as ammo goes. |
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My build was recently completed with a 14.5" Noveske N4 LP midlength barrel, full auto BCG, Sprinco enhanced (blue) spring, and a H2 buffer. It's cycled PMC Bronze 55 grain .223, American Eagle 55 grain 5.56, PRVI 55 grain 5.56, and Blackhills 77 grain OTM 5.56. I haven't had a single hiccup in the less than 400 rounds fired, and all ammo locked the bolt back just fine with Gen1 PMAGs and standard aluminum mags with magpul followers. Brass ejects with decent velocity to about the 4 o'clock position.
I will add that this set up is probably the smoothest and softest shooting AR I've ever shot. Of douse, the Surefire SFMB556 might have something to do with it too, but it shoots from smooth and soft. |
| A M16 rifle's buffer weighs in at around 5.2 oz, while a H3 carbine buffer weighs in around 5.4 oz; so that tells me that it is not port pressure that matters, but instead the volume of the gas impulse. My reasoning is based off an Armalite Tech Note that measured a M4's port pressure at 26,000 psi and a M16's port pressure at 13,000 psi. |
| AR-4C, I didn't measure the gas port prior to installing the gas block. I got excited. Lol. In retrospect I should have. Gonna take the FF rail off to paint the barrel underneath with stove black, so I might as well pull the block/tube at the same time and measure. |
| AIV, just trying to reduce the perceived recoil as much as possible while maintaining 100% reliability. I'm not using a brake on this build, so trying anything I can think of to soften things up and keep me on target for follow-up shots. Plus I like tinkering with things. Haha |
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I was curious to see what your barrel's manufacturer cut the port to. Colt specs a 14.5" USGI M4 port diameter at 0.063". Armalite measured the M4's port pressure to be 26,000 psi. Colt specs a 20" USGI M16 port diameter at 0.093". Armalite measured the M16's port pressure to be 13,000 psi. A 14.5" carbine gas and a 20" rifle gas system both have a dwell time "length" of 7 inches; which a 16" mid-length gas system also shares.
You will notice a pattern develop here. The 14.5" carbine's port diameter decreased 0.030" with the port pressure increasing 13,000 psi. Basing off this pattern the half-way point would make a 16" mid-length gas system have an ideal port diameter of 0.078", and the port pressure should be around 19,500 psi. Now, I understand you are using a 14.5" mid-length gas system; so I'm not sure how this pattern will cross over. |
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"These 14.5" mid length gas barreled upper receiver groups have been specifically tuned to be a very soft and fast shooting set up. They are a joy to shoot, but please feed it good ammo. With good milspec pressured ammo we have been running H buffers. We do not recommend using lower powered ammo. If using less than milspec pressured ammo, it may be best to run a standard carbine buffer." Per the website
You will need and H buffer with the BCM barrel. Spikes 14.5 mid barrel and ST-T2 works great even with wolf and tula |
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Quoted: You can probably got with alittle lighter buffer if you want. This Most people that push the H2, ST2 or other crap really dont deal with the 14.5s and mid GS. This specific combo should start out on a normal buffer/spring or even lighter. Most problems with this combo is undergassed not over gassed |
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Quoted: A M16 rifle's buffer weighs in at around 5.2 oz, while a H3 carbine buffer weighs in around 5.4 oz; so that tells me that it is not port pressure that matters, but instead the volume of the gas impulse. My reasoning is based off an Armalite Tech Note that measured a M4's port pressure at 26,000 psi and a M16's port pressure at 13,000 psi. its both, pressure/volume=energy |
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Quoted:
This Most people that push the H2, ST2 or other crap really dont deal with the 14.5s and mid GS. This specific combo should start out on a normal buffer/spring or even lighter. Most problems with this combo is undergassed not over gassed Quoted:
Quoted:
You can probably got with alittle lighter buffer if you want. This Most people that push the H2, ST2 or other crap really dont deal with the 14.5s and mid GS. This specific combo should start out on a normal buffer/spring or even lighter. Most problems with this combo is undergassed not over gassed I guess I continue to defy the odds. I not only exclusively run H2s in all of my 14.5" mids, but I also run a steady diet of lower powered PMC Bronze thru them as well. Never a single hiccup. And my test group is far more than just a few rifles. |
| Well, gonna sight in the new build today (BUIS, Red dot, etc.) so I think I'll fiddle with the buffer weight at the same time to see what works. I don't have any super weak ammo, but I'll run some M855,M193, Federal AE 5.56 & .223 through it to see what it does. I'll post any interesting results I find. Gonna run the Tubbs CS Flatwire spring for all then a standard carbine spring to check for any differences. We'll see I guess. |
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Quoted:
Ezterra, sounds like a good setup. Is the Springco blue an extra power spring (10% or so)? Yes, the Sprinco blue spring is an extra power spring. I couldn't tell you how much, percentage wise, more power it is. It is noticeably stronger when you pull the bolt back. I will also add that I did test my rifle out with a H buffer before trying the H2 buffer. The H ran just fine as well. I will say maybe there was a very slight reduction in the "punch" of the recoil. In other words, the recoil was slightly softer, or less of a punch when compared to the H buffer. But then again, this could all have been in my head. |
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Quoted:
Yes, the Sprinco blue spring is an extra power spring. I couldn't tell you how much, percentage wise, more power it is. It is noticeably stronger when you pull the bolt back. I will also add that I did test my rifle out with a H buffer before trying the H2 buffer. The H ran just fine as well. I will say maybe there was a very slight reduction in the "punch" of the recoil. In other words, the recoil was slightly softer, or less of a punch when compared to the H buffer. But then again, this could all have been in my head. Quoted:
Quoted:
Ezterra, sounds like a good setup. Is the Springco blue an extra power spring (10% or so)? Yes, the Sprinco blue spring is an extra power spring. I couldn't tell you how much, percentage wise, more power it is. It is noticeably stronger when you pull the bolt back. I will also add that I did test my rifle out with a H buffer before trying the H2 buffer. The H ran just fine as well. I will say maybe there was a very slight reduction in the "punch" of the recoil. In other words, the recoil was slightly softer, or less of a punch when compared to the H buffer. But then again, this could all have been in my head. Not in your head. Sprinco blue with an H2 in a 14.5" mid is as smooth as that configuration gets. |
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I run a noveske afghan with a SureFire brake, a young super light carrier with a carbine buffer and a rifle spring in a carbine tube.
Crazy, I know, but its worked flawlessly for thousands of rounds and is extremely soft shooting and allows for VERY high rates of fire for competition. |
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I just built a 14.5" (pinned) BCM middy for my wife.
We did function tests and fun shooting with a standard spring and H, H2 and H3 buffers. Using PMC Bronze, all three buffers passed the one round in the mag lock back test. However, both of us thought that the rifle shot smoother with the H2 buffer. For some reason the H3 had a strange feel that neither of us could put our finger on, but we both agreed that the H2 was the most comfortable. YMMV |
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UPDATE
Ok, just got back from the "range" a bit ago. Spent the first couple hours breaking in the barrel (Old habits die hard) then a couple more firing different ammo/buffer combos. A Fail Zero M16/M4 BCG was used throughout as well as a Tubbs CS Flatwire buffer spring. Weapon used was my new 14.5" BCM bhf barreled upper with an A2 FH. Buffers used were a Carbine, H and H2. Ammo used was M855 Green Tip, M193, Federal 5.56 and AE 55 grain .223. Results: Zero FF/FE with any buffer/ammo combination Bolt lockback every time upon emptying magazine (Pmag gen3, C products 30 rd aluminum with magpul follower) All cases were ejected in a neat pile at about 1530 regardless of ammo/buffer used Perceived recoil was noticably less with the H2 buffer vs the Carbine buffer Unable to measure bolt bounce as I lack the needed camera In addition, sighted in the M3 2moa red dot. If I can get the pictures to load, I'll show the last grouping fired at 100 yards using M855 (and a 3x magnifier..lol). |
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