So I have two uppers that I’m planning to have share a single lower. They are both KAC SR-15 Mod 2’s, one being the 14.5" with a MAMS and the other being the 16" with the standard KAC 3 prong. I am a little torn between putting a standard RE with the buffer that the 14.5" came with and using a VLTOR A5. I did some searching but found very little discussion about the 16" in particular. For what it’s worth I have the A5H1 buffer on hand.
The amm I’m concerned about is Wolf Gold, PMC Bronze, along with a little Tula. The rest of the ammo I have is 5.56 (IMI, MEN, various Green Tip) so I’m not too concerned about it being underpowered for the A5.
Does anyone have experience with these setups? I would take them out and try it, but I want to stake the castle nut so eventually I’ll be locked into one configuration.
I have the 11.5 kac cqb running a sprinco green + a5H2 vltor system, and it’s running perfectly fine, not dents on brass casing, normal ejection distance… etc. I’ve read some reports that the 16" and longer sr15 guns might have issues with the vltor system though, but i think 11.5 and 14.5 are fine.
This is a dumb question. Sorry, not sorry. It’s the truth.
The answer is simple: KAC SR-15s will cycle any of the ammo listed, regardless of the buffer.
If you want to split hairs with the AR-15 platform, and are building from the ground up, the A5 buffer system is the best-case engineering answer. If you’re buying complete rifles (at KAC prices, no less), just run what works; which is to say, stfu and shoot your rifle.
I like the directness. I’m putting the factory uppers on a lower I’m putting together myself, hence the question. Sounds like the A5 is the way to go, thanks for the help guys.
Our in-house testing indicates that the most reliable setup for SR-15s is with the KAC provided buffer, standard receiver extension, and standard spring, with action spring replacement every 5,000 rounds or so. Design parameters cover ammunition from 55gr PMC to Mk 262 Mod 1, suppressed and unsuppressed. This is not terribly surprising, as these are the variables that the guns are designed, built, and tested around.
If you are willing to cede some aspect of the design intent for a gain in another aspect, that’s certainly your choice to make, I simply have not seen any real gain with SR-15s (as opposed to carbine length gas systems) by going to the A5.
If you’re concerned, don’t dick with it. Unless you know something the engineers at KAC don’t know, I’m not seeing a compelling case to spend that kind of money on an upper only to turn around and potentially cause yourself problems chasing an incremental reduction in felt recoil. I tested mine with an H buffer and it ran but it narrowed the window of operation when dirty. YMMV.
I think I asked you this before, but precisely how heavy (oz) is the KAC buffer? I own a SR-15 Mod 2. Haven’t had a chance to shoot it yet, nor do I own a scale to weigh the buffer.
As an aside, considering how cheap 5.56 NATO spec M855 is, I am uncertain as to why anyone would want to feed a KAC upper Wolf or Federal XM193 ammo (which is analgous to hitting Top Flight X-outs with a $500 titanium driver).
The assumption is that a buyer of an upper will either be putting it on a KAC lower (which comes with the standard buffer), or their own, which is most likely to already have a suitable buffer.
Since the 11.5 and 14.5 are designed around an H2 buffer (counter to the far more common 16" and 18" guns), we throw it in.
Standard weight buffer is 3.0oz.
H2 (21057) buffer weighs 4.7oz.
I actually do shoot quite a bit of PMC through my personal guns. Mostly for Run-n-gun type competitions inside 50. Lots of those places don’t allow M855, mostly with regard to steel, and I don’t want to chance accidentally throwing in a mag of 855 and getting DQ’d. PMC matches my POI for a lot of my precision-ish ammo, so I’m not thinking about offset differences should I need to use it a mid-range. Also, when I let folks try the gun out, I don’t want to burn my “good” ammo, so they get PMC. But yeah, no XM193 for me, thanks.
I have an SR15 Mod 2 with an A5 system. I’ve never had any reliability issues, but the power disparity between weak-ass Wolf .223 and regular military M193 is much more apparent. Still no malfunctions, though. I really appreciate the smoothness the A5 gives you.