16” comparison: DD 16” mid-length with BCM A5 lower vs Knight’s SR-15 MOD 2...

[Wake27]

Wow that's good to know. I didn't know they have bigger gas ports. I bought mine in 2014 so I have no idea which I have.

But it hardly cycles unsuppressed. With a Green Spring it wouldn't load the next round, so I switched to a standard spring. With a suppressor it's a dream.

Jack actually responded to him in a different thread about it. I think it was something to the extent of them opening it up just enough that it’ll still reliably cycle brass .223 when dirty.

As for the green spring, I’ve seen some interesting stuff on that lately regarding Hodge and KAC and have since switched all of my guns over to standard springs. That way they can all reliably run with an A5H2 if not A5H3. I was having issues with the green spring A5H2 combo on my unsuppressed 14.5 Mod 2, but the standard spring seems to have fixed that.


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[Wake27]

I had an early Mod1 upper and it was awesome. I shot it until it keyholed.

Got the barrel replaced with a new one with the bigger gas port and decided it was just like anything else and never went back to KAC.

KAC uppers being just like everything else is pure fake news.


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[MadAngler1]

@MadAngler1

Thank you for the quality post. Very interesting (and honest) observations and comparison in general.

Few questions:
- Why do you say that A5H1 is better other weights? I've run A5H0 and A5H2 and I would think that A5H2 (or even A5H3) buffer for 16" would work fine, especially with the can
- Have you tried running H2 buffer in KAC? I suspect that it will run just fine with it especially with a NATO ammo.
- How do guns balance (with and without corresponding cans)?

I don't own a can, but I'm really surprised that you say that Surefire can is quieter. Most people I've heard say otherwise.

Thanks. If you click on the ARFCOM link above, it’s my long post in the KAC forum highlighting all the things I tried on the SR-15. H2 and H3 won’t reliably cycle 5.56 NATO pressure loads in the mod 2 SR-15 without a suppressor attached. Both weights are great suppressed however.

For the A5, I can run the rifle with a A5H2 buffer suppressed and unsuppressed, but the ejection pattern unsuppressed is 4 to 5 o’clock. With a A5H1, the ejection patterns are 2-3 o’clock and I don’t see the bolt struggling to cycle as much. It just seems to like the A5H1 better suppressed and unsuppressed. It runs smoother, less bolt bounce and less felt recoil (no heavy buffer slamming the buffer tube).

I think the DD mid-length is the heavier of the two. It balances OK though with the BCM buttstock. The KAC is lighter but more muzzle heavy with the magpul carbine stock. This is with the cans on. Without the cans, both balance quite well. DD’s V7 MLok handguard feels great, as does the URX4. Both of these set ups really are nice if you intend not to run a can. Put on a can, it becomes a different ball game entirely.

All in all, if I had a do over, I would have just bought the A5 lower and DD upper. I already own 3 other Surefire cans. I could have saved myself $1400 and not bought the KAC can for the SR-15. I’m strongly thinking about buying a Barrett Rec 7 since it possesses an adjustable gas block....either that or a SCAR-16. I wanted a 16” carbine for courses that could do it all, so I wouldn’t have to swap buffer weights, etc. Right now, the A5 with a DD mid-length will be the one. I don’t need to worry about switching anything out when adding the SOCOM 556 RC2.

[MadAngler1]

Jack actually responded to him in a different thread about it. I think it was something to the extent of them opening it up just enough that it’ll still reliably cycle brass .223 when dirty.

As for the green spring, I’ve seen some interesting stuff on that lately regarding Hodge and KAC and have since switched all of my guns over to standard springs. That way they can all reliably run with an A5H2 if not A5H3. I was having issues with the green spring A5H2 combo on my unsuppressed 14.5 Mod 2, but the standard spring seems to have fixed that.


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That is my understanding as well. They opened the ports up on the 16” Mod 2s (over the Mod 1s), because too many people want to run cheaper .223 spec ammo over NATO pressure stuff.

I was told to try the Sprinco springs, and I managed to find the correct weight combos to make them work. It’s a matter of swapping weights relative to the spring constants (F = kx from my physics days, with k = spring constant in newtons/meter). Basic physics. It’s amazing how as little of 0.5 oz can make a huge difference in how the gun cycles. I turned both rifles upside down, sideways, to make sure they ejected unsuppressed and suppressed. They work. The only thing I didn’t do was add mud.

[MadAngler1]

KAC uppers being just like everything else is pure fake news.


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KAC uppers are different animals. You have to respect their bolt design for starters. There are samples in the wild with 15-20k rounds running strong. The problem is out of the box, it comes with a carbine spring and buffer. Does not work as advertised shooting NATO spec ammo with THEIR QDC 556 suppressor. That is what was upsetting to me. I spent $2250+1400 for the rifle and the can. I could have spent it elsewhere.

[MadAngler1]

and I’d like to add that we should all give VLTOR credit for the ingenious design of the A5 set up. It really does work as advertised when you set it up right with the right suppressor.

[Wake27]

KAC uppers are different animals. You have to respect their bolt design for starters. There are samples in the wild with 15-20k rounds running strong. The problem is out of the box, it comes with a carbine spring and buffer. Does not work as advertised shooting NATO spec ammo with THEIR QDC 556 suppressor. That is what was upsetting to me. I spent $2250+1400 for the rifle and the can. I could have spent it elsewhere.

Did you reach out to them about it? I didn't buy a complete gun from them so I didn't think of it initially, but if you're talking factory rifle with can having issues, that's definitely something I'd reach out to the about.

[MadAngler1]

Did you reach out to them about it? I didn't buy a complete gun from them so I didn't think of it initially, but if you're talking factory rifle with can having issues, that's definitely something I'd reach out to the about.

The issue is excessive gas to the face. The gun “runs” fine suppressed and unsuppressed from the factory. The problem lies when shooting suppressed with the factory set up, you get a ton of gas to the face. So much in fact that after 5 rounds, you have to stop shooting to wipe your eyes (even when you have Wiley X’s on). My DD out of the box was slightly over gassed but didn’t do that.

[Wake27]

The issue is excessive gas to the face. The gun “runs” fine suppressed and unsuppressed from the factory. The problem lies when shooting suppressed with the factory set up, you get a ton of gas to the face. So much in fact that after 5 rounds, you have to stop shooting to wipe your eyes (even when you have Wiley X’s on). My DD out of the box was slightly over gassed but didn’t do that.

I’d still ask them about it. KAC uppers and cans both have reputations for being very tame so it makes me wonder if something else is going on. Especially with such a long gas system.


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[MadAngler1]

I’d still ask them about it. KAC uppers and cans both have reputations for being very tame so it makes me wonder if something else is going on. Especially with such a long gas system.


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I did speak to them on ARFCOM. I got the impression there was nothing wrong. I guess I’ll send them another formal email.