First shots with my KAC SR15 MOD2

[Failure2Stop]

Any problems with running weak .223 in an SR-15 with A5 setup? I heard to stay away from weak ammo for SR-15's, but at the same time this was from people that don't have the A5 set up in their SR-15's. Does the A5 add anymore reliability?

I know the SR-15 has a slightly elongated gas system, so I was unsure of how this would pair with the A5

Cannot comment on the A5, as we don't test with it, but the ammo used for function test from the factory is PMC 55gr.

[Tzook]

Any problems with running weak .223 in an SR-15 with A5 setup? I heard to stay away from weak ammo for SR-15's, but at the same time this was from people that don't have the A5 set up in their SR-15's. Does the A5 add anymore reliability?

I know the SR-15 has a slightly elongated gas system, so I was unsure of how this would pair with the A5

I am not currently running that set up, but I have in the past. I shot a decent amount of Tula through it and I never had a problem, or not anything that comes to mind anyways. Should be good to go.

[BufordTJustice]

Cannot comment on the A5, as we don't test with it, but the ammo used for function test from the factory is PMC 55gr.

Perennially weak stuff, in my experience. That gives plenty of margin for function.

[w3453l]

Thanks to all in regards to the A5 question. I stay away from steel case, but it's good to know that it'll still run. I've been stocking up slowly on 5.56, but the recent stupidity surrounding 62 gr ammo forced me to stray away from the usual 5.56 and start buying .223.

Waiting on the 14.5 with MLOK; sorry OP for the thread jack.

[tom12.7]

On the MOD1 SR-15's 16" models, I have used a specific porting for the A5H2 standard action system that seems to mimic close to the action speed of the the 14.5" KAC models with that action system with good results so far. It is more reliable than what I thought it would be and smooth. Still working on the MOD2 version, as it seals the gas block tighter.

[Plasman]

I'll also try throwing it on a lower with milspec carbine action spring and CAR buffer, but I'm still skeptical it'll be any better than with the A5 setup and BCM middy + A5 combo...

So I finally had the opportunity yesterday to bring the MOD 2 upper out along with two different lowers (one with PWS .308 EBT (A5 length), the other with standard milspec RE), various buffers (CAR through H3 and A5H0 to A5H3), and various action springs (BCM carbine spring, Sprinco Blue, VLTOR rifle spring, and Sprinco Green). Ammo used was Wolf Gold 55gr.

My success criteria was the least amount of perceived muzzle movement for faster follow-up shots. To aid this I used the KAC micro iron sights to restrict and focus my view (movement away from initial POA is more easily noticed). I also brought my GF along to see if her opinion of each system matched mine. She doesn't shoot much and doesn't know/have an opinion on what the various buffers and action springs should/might do, so it was good for a blind test.

I'm going to eat a little crow on what was settled on as the optimal combination, which ended up being the milspec RE, CAR buffer, and Sprinco Blue spring. I say "a little" crow, because using a stock carbine spring (factory setup) was noticeably less optimal and both my GF and I agreed on that (actually she agreed with me on all my conclusions without me stating them before she gave her impressions so I guess I was able to stay objective).

The runner up combination was the VLTOR A5 RE, A5H0 buffer, and Sprinco Green spring. I noticed a longer cycle time with this and the recoil impulse of the buffer hitting back seemed a bit harsher than with the optimal setup, but not really significantly so.

When using the standard BCM carbine spring or VLTOR rifle spring with their respective setups the felt recoil impulse was greater than the top setups.

If any heavier buffers were used on either setup there were two distinct impulses of the buffer hitting the rear of the RE and then BCG going back into battery that threw the muzzle off. While they did decrease the felt recoil, overall controllability suffered. The MOD 2 likes a fast cycle time.

[tom12.7]

So I finally had the opportunity yesterday to bring the MOD 2 upper out along with two different lowers (one with PWS .308 EBT (A5 length), the other with standard milspec RE), various buffers (CAR through H3 and A5H0 to A5H3), and various action springs (BCM carbine spring, Sprinco Blue, VLTOR rifle spring, and Sprinco Green). Ammo used was Wolf Gold 55gr.

My success criteria was the least amount of perceived muzzle movement for faster follow-up shots. To aid this I used the KAC micro iron sights to restrict and focus my view (movement away from initial POA is more easily noticed). I also brought my GF along to see if her opinion of each system matched mine. She doesn't shoot much and doesn't know/have an opinion on what the various buffers and action springs should/might do, so it was good for a blind test.

I'm going to eat a little crow on what was settled on as the optimal combination, which ended up being the milspec RE, CAR buffer, and Sprinco Blue spring. I say "a little" crow, because using a stock carbine spring (factory setup) was noticeably less optimal and both my GF and I agreed on that (actually she agreed with me on all my conclusions without me stating them before she gave her impressions so I guess I was able to stay objective).

The runner up combination was the VLTOR A5 RE, A5H0 buffer, and Sprinco Green spring. I noticed a longer cycle time with this and the recoil impulse of the buffer hitting back seemed a bit harsher than with the optimal setup, but not really significantly so.

When using the standard BCM carbine spring or VLTOR rifle spring with their respective setups the felt recoil impulse was greater than the top setups.

If any heavier buffers were used on either setup there were two distinct impulses of the buffer hitting the rear of the RE and then BCG going back into battery that threw the muzzle off. While they did decrease the felt recoil, overall controllability suffered. The MOD 2 likes a fast cycle time.

I'm not knocking your criteria if what you stated was your end goal. I would like to make a few points though. For a wider range of reliability, meaning many things, it is hard to beat the consistency of the A5H2/ Colt rifle spring/ with specific porting for general use in almost any combination of components. Softer, smoother, quicker, less wobble, etc, take second hand to reliability/durability in serious use guns. Specific/ non-factory porting is needed in this combination, and produces the appropriate results. One of the clues you find in these is a narrower change in carrier velocities with the other changes, like ammo selection, etc
If it is just a fun gun, run it how you wish. If it is serious, make it more reliable and durable.

[Plasman]

I'm not knocking your criteria if what you stated was your end goal. I would like to make a few points though. For a wider range of reliability, meaning many things, it is hard to beat the consistency of the A5H2/ Colt rifle spring/ with specific porting for general use in almost any combination of components. Softer, smoother, quicker, less wobble, etc, take second hand to reliability/durability in serious use guns. Specific/ non-factory porting is needed in this combination, and produces the appropriate results. One of the clues you find in these is a narrower change in carrier velocities with the other changes, like ammo selection, etc
If it is just a fun gun, run it how you wish. If it is serious, make it more reliable and durable.

I'm not really following your rationale. If you're just going to modify the gas port for a specific non-standard buffer system, why bother getting an SR-15 in the first place? Couldn't you do the same with a cheaper mid-length barrel? It also sounds like you're saying the SR-15 doesn't have a reliable system.

[tom12.7]

I'm not really following your rationale. If you're just going to modify the gas port for a specific non-standard buffer system, why bother getting an SR-15 in the first place? Couldn't you do the same with a cheaper mid-length barrel? It also sounds like you're saying the SR-15 doesn't have a reliable system.

I'm thinking you are missing the point I was making on reliability/ durability. The rifle like A5 action system is a more reliable and durable system than the carbine buffered carbine action system. An AR would need the appropriate port size to see the benefits in the those regards. A carbine that is gassed for a carbine action H2 buffer can usually switch to the A5 type of system with improved results, as they would see an improvement from a carbine action system gassed for the lighter carbine or H1 buffer.
SR-15's are a pinnacle product, meaning that they are basically the best items to run. That does not mean that there are no ways to improve upon the product. I could make or buy rifles using non KAC products, but I choose not to do so, as I like the attributes of those pinnacle products.
How an interpretation could be made that SR-15's aren't reliable from my statements is beyond me? MRBS and MRBF was my point. Saying any item can't be improved when there are known ways to do so, doesn't always mean they choose not so from the same perspectives as others.

[Plasman]

How an interpretation could be made that SR-15's aren't reliable from my statements is beyond me?

What about my preferred buffer system setups with the SR-15 upper makes you believe they're any less reliable than what the SR-15 comes with from the factory? I don't believe there's any reliability compromise with them at all over stock. Given that the scope of the discussion (going back) was about perceived smoothness and felt recoil with the intermediate gas system, bringing up reliability was outside of that, and indicated you saw an issue with the stated setups. Furthermore, pointing out how my success criteria came second to reliability and all that "hard use" talk also implies that there's a deficiency with the reliability as is.

I don't disagree with you on your buffer system to reliability relationships, but it was scope creep from the original discussion and thus implied you were pointing out a flaw with the original system. You may like the SR-15 for other attributes, but given the discussion was focused on the gas/buffer/recoil system, which you stated you change completely, it's not hard to question why you would bother starting from such an expensive system in the first place.