KAC SR-16 Pressure Reduction System

**mtdawg169** · 01-21-14, 21:37

Originally Posted by tom12.7

The added difference isn't really the felt "feel", it is the difference in a broader range in "reliability" of the A5 system has to offer in the KAC rifles.
The KAC rifles are great, it can be a way of making them even better to insure consistent function.

I wasn't really referring to feel. The SR15 is pretty reliable as-is and generally needs the lighter A5H1 if you're going to run the A5. My intent was to point out that the A5 offers the most advantage on the SR15 if you need added reliability for suppressed & unsuppressed use with a wide variety of ammo. If a suppressor isn't in the mix, I don't personally see a need for it.

**hjmpanzr** · 01-21-14, 22:10

Originally Posted by mtdawg169

I wasn't really referring to feel. The SR15 is pretty reliable as-is and generally needs the lighter A5H1 if you're going to run the A5. My intent was to point out that the A5 offers the most advantage on the SR15 if you need added reliability for suppressed & unsuppressed use with a wide variety of ammo. If a suppressor isn't in the mix, I don't personally see a need for it.

Agree. If not running suppressed its a luxury. I don't have any KAC 16" uppers left as I've swapped them for 14.5s but I ran several thousand rounds thru legacy two SR15s using 223 (TAP and BHA so quality stuff) with no malfunctions. Ran it in the heat, the cold the rain and at least half the time it was suppressed. At the time I wasn't aware that they had an A5H1, and maybe they didn't. It was back when you had to get the entire emod kit.

But I did have a first this evening. I had a FTE on a 14.5" while shooting suppressed using BHA Remanuf 223. No A5 on it yet so it just had the standard H2 on a regular KAC SBR. It was a surprise. My second FTE on any KAC. Both times have been with 223 and the previous one it was with Russian crap. It happens so rarely that it was almost fun clearing the chamber with a real FTE.

**mtdawg169** · 01-21-14, 22:24

Originally Posted by hjmpanzr

Agree. If not running suppressed its a luxury. I don't have any KAC 16" uppers left as I've swapped them for 14.5s but I ran several thousand rounds thru legacy two SR15s using 223 (TAP and BHA so quality stuff) with no malfunctions. Ran it in the heat, the cold the rain and at least half the time it was suppressed. At the time I wasn't aware that they had an A5H1, and maybe they didn't. It was back when you had to get the entire emod kit.

But I did have a first this evening. I had a FTE on a 14.5" while shooting suppressed using BHA Remanuf 223. No A5 on it yet so it just had the standard H2 on a regular KAC SBR. It was a surprise. My second FTE on any KAC. Both times have been with 223 and the previous one it was with Russian crap. It happens so rarely that it was almost fun clearing the chamber with a real FTE.

Interesting. Did it stovepipe or short stroke?

**hjmpanzr** · 01-21-14, 23:18

It was a bit odd but best described as stovepipe with a twist of double feed. Looking at all my gear I realized it was a magazine issue. I was using a really old worn mag that I used in the 80s for rabbit hunting and such as a teen. I recently put a magpul anti tilt in and I forgot I had thrown it in the range bag. This was the first time out since repair. That possibly combined with a new suppressor for the rifle (surefire FA556 MG rated I usually use the SF 556-212). I'm going to pull the follower and toss the mag.

**tom12.7** · 01-22-14, 18:10

The regular Colt rifle (A2) spring is more forgiving in a broader range than the carbine (M4) spring, given the proper buffer weight (total reciprocating mass) for the application. What this means is that it can cycle successfully better with a wider range of ammo, fouling, temperature, lack of lube, suppressed, etc. etc.
For an existing setup, low density (read cheap) tungsten buffer weights, a mill, and spacing come into play to make incremental changes like A5H1.5, A5H2.5 buffers that can work well.

**BufordTJustice** · 01-22-14, 18:37

Originally Posted by tom12.7

The regular Colt rifle (A2) spring is more forgiving in a broader range than the carbine (M4) spring, given the proper buffer weight (total reciprocating mass) for the application. What this means is that it can cycle successfully better with a wider range of ammo, fouling, temperature, lack of lube, suppressed, etc. etc.
For an existing setup, low density (read cheap) tungsten buffer weights, a mill, and spacing come into play to make incremental changes like A5H1.5, A5H2.5 buffers that can work well.

Edit: i just re read your post.

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**mtdawg169** · 01-26-14, 18:47

Short update. I ran approx. 150 rounds of old Guatemalan M193 and some new Prvi M193 through the KAC SBR yesterday with the E-carrier. All fed and functioned 100%. I'm going to keep it in the gun and run a couple hundred more rounds of full power ammo through it before trying the PMC again.

On a related note, I also have one in a 17" rifle gassed Noveske build (complete enhanced bolt carrier group and standard carbine receiver extension). That rifle short stroked yesterday with MK262 and had a few failures to lock back, approximately 60% of the time. Never had that issue crop up before with that gun. Previously, in warm weather, that gun has been good to go with MK262 and 223 match loads. May have been the slightly cooler temps, but it was in the high 40s here yesterday. I'm going to try that gun again with a standard Carbine buffer and see how it goes. Currently running an H buffer.