Background, I recently finished my 11.5 with A5 sbr and in happy with it. I followed the credible advice I found, and it seems agreed upon that these two elements are valuable
I recently was doing some department shooting and the conversation came up, once in tech talk and once with a buddy that has a DD 10.3.
When asked why this over the 10.3 , my answers were basically that there is a theoretical benefit.
With the 11.5 we’ve all seen the bcm explanation on dwell time, I estimate you get maybe 75-150 more velocity but the data claims are all over the place, but I don’t know of any factual examples of reliability issues.
With the A5 it’s easier when people recount it being smoother or not carrying multiple buffers anymore.
But when it comes to reliability, are there examples where either make the difference between a gun functioning or not, or is it all a theoretical improvement?
Again, I’m happy with the set up, just wondering if there is a more concise explanation vs some long winded discussion
It’s an incremental improvement, not a totally different type of capability. Dwell time, especially for SBR’s is really helpful (it doesn’t need to be overgassed to run slightly lower pressure stuff - something the DD 10.3" setups opt for overgassed on).
A5 is a lot of the same deal - subjectively a bit smoother, but the selling point of that on a lower is that one has to go to one extreme or the other to make the carbine no longer run correctly - most people wouldn’t consider it worth replacing a good mil-spec H/H2 setup on a carbine, but if you’re building from scratch and are fine with using a longer stock (EMOD, ACS, ACS-L) or don’t mind if it doesn’t collapse all the way, then I’d say it’s silly NOT to put an A5 on a lower.
It’s definitely possible to make an SBR work in MK18 with Carbine RE buffer systems - it’s just not quite as flexible on width of gas impulse envelope for reliable performance. I personally run a 10.4" with A5 setup on my double stamp SBR, but when this upper wears out it’ll get replaced with an 11.5" unit; but the VLTOR A5 lower with ACS on it has become my standard lower receiver - I now have three Noveske Gen2 Flared Forged lowers, two with VLTOR A5/ACS and the other is an A5/EMOD - and I don’t need any other lowers.
the other thread made me wonder, I went with a good forged lower, but is it the supposedly advantage of a forged lower over billet also completely theoretical?
Forged 7075 against billet 6061 is a difference that isn’t exactly theoretical to me - one awkward fall and I know I’d break the billet unit - the forged no questions asked that it’ll shrug that off (FWIW, I’m at a mildly tubby 233lb right now).
My only long term experience with an SBR is a Colt 6945 (10.3" on a Colt M16A1 lower with a Colt carbine extension and an H3 buffer). It sometimes gets used with a Gemtech suppressor. The only magazines it has ever seen are green follower Centers.
It has always shot .223 and 5.56 without any reliability problems, full-auto, suppressed or not. It belongs to a buddy of mine and he does not lube the gun ever. Says it blows too much black shit in his face.
He also uses a 20" Colt upper, some 7.5" pistol upper, and a 16" Colt 6720 upper on that lower and has 0 reliability issues.
I had a BCM 11.5" back before they sold a 12.5". I don’t have it anymore, but it was great. Perfectly reliable.
I decided for short stuff I would switch to 300blk, that is the only reason I dumped the 11.5".
Personally, I ALWAYS opt for the longest barrel I can get away with. Why? Because I never say, “no,” to muzzle velocity. As long as the size isn’t going to hinder my ability to do work, I choose the longest option for a task. If BCM made a 12.5" when I purchased the 11.5" I would have gotten that instead.
Thanks for your insight on barrel length. Your rule is solid and makes sense to me, plus it’s a refreshing bit of sense in the latest craze to get the shortest barrel possible.
Works for me also. I choose the MK262 loads for all my 11.5 SBR rifles. Even past that 320 yard range, I sure as hell would not want to be hit by a 77gr projectile even at much less FPS.
A properly built and designed gun SHOULDN’T need an A5 system just to function. However, the benefits of the A5 system are undeniable.
Slower extraction, stabilized cyclic rate, stabilized extraction speed, more time for the round stack in the magazine to present subsequent rounds for proper feeding, longer spring life, more controllable, and more accommodating of ammunition that varies greatly in pressure and/or bullet weight.
There is literally no downside, and the improvements are far from theoretical. Adding functional operating margin to an already reliable weapon without any negative side effects is the friggin HOLY GRAIL of the AR15 aftermarket community. Who doesn’t want a gun that is more controllable AND more reliable?
This right here is why I run the A5 even on my Mk18 upper - even though I’m giving up 35yd or so of effective Mk262 envelope, I was able to make a carbine with a tiny suppressor mounted that still fits in a standard tennis racket case (30.5" OAL), and it out and out runs suppressed. Since the extended length stocks are the only ones that don’t consume facial hair and fractions of my soul to use, then A5 is an absolute no-brainer.
