I have an SR15 Mod1 with an A5 kit installed. It shoots very smoothly with M193 and M855. Underpowered .223 feels very sluggish, but it always cycles.
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I have an SR15 Mod1 with an A5 kit installed. It shoots very smoothly with M193 and M855. Underpowered .223 feels very sluggish, but it always cycles.
Good to hear, so you fellas recommend the stock A5 H2 buffer the kit comes with and no messing around with an H4 or H4 on the SR-15 upper?
Look up the thread in the technical discussion area last posted 2-2-14, titled SR 16 pressure reduction.
Read from the middle of page 1 to the end. https://www.m4carbine.net/showthread...duction-System
It's pretty much all about A5 system on various KAC uppers. The 16" will likely be very different from the 11.5". I have a factory KAC SBR CQB 11.5" and it will take a A5H4 for PMC bronze. However, my KAC carbine 14.5" runs everything perfectly fine with the A5H2 (MK262, XM193, BHA 77 gr 223, and PMC bronze. The 11.5" has a carbine length gas system as opposed to the intermediate gas system in KAC 14.5" and 16" uppers.
Moreover, there's going to be some changes to the gas system on the mod 2 so there's not really anyone who can say one way or the other. You would think there shouldn't be that much of a difference but I ran an 11.5" SR-16 upper with a regular (non-A5 H2) and it ran fine but the 11.5" SR-15 not so much even though they apparently have the same sized gas port although I'm really questioning that point.
Hjmpanzr, I'm kind've surprised about your A5H4 results? I have multiple block 1-3 examples, multiple newer URX 3.1's, and dimpled SR-16 11.5's. None will take that buffer with PMC bronze. I have a new upper from a week ago, plus another that'll arrive tomorrow that I can try out.
It surprised me as well. I'm a bit partial to the 14.5" carbine so I've mostly been shooting those rifles and when I had been shooting a KAC 11.5 it was the SR-16 11.5 (w/ dimpled barrel, URX 3 mid-length rail, chromish bolt, etc) and it ran great on an H2. Then I spent most of the winter and early spring shooting KAC carbines (with Vltor A5s). In mid April form 4 came back on the KAC SBR CQB 11.5 with URX 3.1 (purchase made in late July 2013). I took it to the range expecting very similar results as I had with the SR-16 but it was very different. I was shooting XM193.
I went home that night and put on an A5. I went to the range again shortly thereafter and started with an A5H2, then to A5H3 and finally A5H4. The H4 smoothed it out pretty well. I wondered whether it would have any problems with 223 so I ran BHA 77 gr 223 and PMC bronze. The rifle eats it up fine. I've not had any problems with it. It functions fine with my surefire suppressors as well.
This last weekend I ran it at a class and it functioned perfectly. But it's very gassy without an A5 system. In fact, I wouldn't have used it in the course without the A5. It's a necessity for this rifle. That said, I can't really square it with my experience with the SR-16; very different.
I'll be interested to hear how your new one runs.
I'll try to get the new ones out this weekend, I'm getting curious on this. Either they changed the gas port spec, or yours is oversized. I really hope the spec hasn't changed. You may want to contact KAC on this.
I have had the same troubles. My last 3 KAC 11.5" uppers have been overgassed as well. I am currently going to try an H3 buffer and maybe a LMT Enhanced carrier. Really noticeable once I put the can on. I have to agree that the SR16 has a smaller port. Going to have to pull my gas blocks and find out.
I have what believe to be a small port mod.0 upper.
MFS .223 55gr. zinc steel case do not lock back on the A5 extension with its standard buffer. I run it on a carbine spring and SR15 marked buffer and Federal .233 55gr. brass case did not lock the other day at the range.
Prvi 75gr. 223 lock back on both as does federal .223 62gr GD Fusion MSR.