View Full Version : 16” comparison: DD 16” mid-length with BCM A5 lower vs Knight’s SR-15 MOD 2...
MadAngler1
05-23-20, 00:04
I posted this on the OTS, so I figured I’d post it here as well.
Short conclusion: If running suppressed, you’re probably better off buying a 16” mid-length upper with an A5 lower vs shelling out extra money for a Knight’s SR-15.
Rifle 1: BCM lower with A5 receiver extension (purchased on sale from G&R tactical). Upper is a Daniel Defense V7 mid-length 16” with a Surefire flash hider and Surefire SOCOM 556 RC2 can. Trigger is stock BCM, charging handle Geissele. I found the best buffer was the A5H1, which for me was actually ~4.7 oz since I took a Slash Heavy buffer and removed weights to make it a A5H1. Using a sprinco green spring, I can run the gun suppressed and unsuppressed without any issues (no malfunctions) using NATO ammo and 77 gr SMKs. The gun is very accurate (as accurate as the Knight’s) and doesn’t require a proprietary bolt or wrench for the handguard. I also like the heavier profile barrel, and mind you, the port diameter (per DD) is 0.077” which is slightly smaller than most.
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Rifle 2: Knight’s SR-15 MOD 2 16”, Knight’s QDC 556 suppressor. To get it to run suppressed without throwing gas in my face constantly, I had to take out the stock carbine spring and Knight’s carbine weight buffer (yes, they do not use a H buffer in the 16” MOD 2, just carbine weight), I put in a H weight buffer and Sprinco blue spring. This allow me to run it suppressed and unsuppressed without any malfunctions, in conjunction with a Radian SD Raptor charging handle. The charging handle played the biggest role in cutting out the gas to the face I found, even more so than a Geissele CH. One can read the full saga here: https://www.ar15.com/forums/Industry/SR-15-16-Mod-2-with-QDC-556-suppressor-gas-blow-back-/381-294356/
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I have now 1000 rounds through each rifle. I can say these things:
1. Both are 100% reliable now with the above set ups, suppressed and unsuppressed. It took a lot of work and play, but I got them right. I am running NATO pressure ammo or 77 grain SMKs though. I am not using junk .223 pressure stuff.
2. The DD + A5 receiver extension shoots softer than the Knight’s SR-15 both suppressed and unsuppressed. It is very noticeable. The A5 receiver extension makes a huge difference, especially when you need a slightly heavier buffer to run suppressed.
3. I like the way the QDC suppressor attaches to the flash hider more than the Surefire. However, if one uses ALG Go Juice inside the can’s attachment and the flash hider, this becomes a non-issue when it comes time to take off the can. (Thanks to JoshNC for the Go Juice tip)
4. The Surefire is more quiet than the QDC can. It is noticeable to myself and my friends when shooting.
5. Accuracy is more or less the same between 25-100 yards, red dot or scope, etc. The Knight’s trigger of course is better, but I can drop a Geissele easily in the Bravo Company lower.
So if I had a do over, I would not have bought the Knight’s. In fact, I’m thinking about selling it (sorry Jack, but thanks for convincing me to purchase one two years ago). As much as it hurts to part with a rifle that works, I rather put the money towards something else. Thoughts?
Leonidas24
05-23-20, 02:06
Does the buffer for the SR15 have a part number printed on it anywhere? Or is it a plain, gold-ish anodized unmarked buffer?
MadAngler1
05-23-20, 07:52
Does the buffer for the SR15 have a part number printed on it anywhere? Or is it a plain, gold-ish anodized unmarked buffer?
It says SR-15 on it. I’ll have to look again about the part number.
Try swapping uppers and let us know what you're seeing.
Wouldn't be shocked if the SR15 on A5 lower was the best of both worlds
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Try swapping uppers and let us know what you're seeing.
Wouldn't be shocked if the SR15 on A5 lower was the best of both worlds
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KAC with A5 is amazing. I have a Mod1 suppressed with a Surefire and it's the softest shooting AR I've had.
MadAngler1
05-23-20, 13:06
Well I guess I could try that next. KAC didn’t recommend that, let alone anything else I tried.
Wouldn’t it be crazy to have two non-Bravo company uppers on Bravo company A5 lowers? :p
@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.
KAC with A5 is amazing. I have a Mod1 suppressed with a Surefire and it's the softest shooting AR I've had.
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.
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.
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.
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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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
05-24-20, 12:16
@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
05-24-20, 12:19
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
05-24-20, 12:21
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
05-24-20, 12:23
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.
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
05-24-20, 19:52
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.
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
05-25-20, 11:36
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.
KAC with A5 is amazing. I have a Mod1 suppressed with a Surefire and it's the softest shooting AR I've had.
I’ve been running an A5 on my Mod 2 for quite a while now. It’s smoother for sure
My SR15 with QDC wouldn't lock back on Colt 20 round mags. I found out that Colt springs in their 20 rounders are kind of weak. Worked fine with Magpul Gen3. I put an A5 in mine as I do in every gun. There is just nothing like the A5 IMO. Love my SR15 with QDC. Kinda barky but such is life. Without the CAN, the MAMS is a work of art.
PB
I’d agree, you still have a very light, CHF, light weight with great BUIS, the bolt/extension, etc.
Mod 2 is also much finer tuned. I dunno. I think if your single criteria is soft / smooth shooting - it’s easy to build that out.
They refined the gas block to help with gas leaking, etc. with the traditional design.
I only say this because I feel a gun that didn’t malfunction and manufacturer being maligned that wasn’t contacted if you had an issue. Just seems a bit heavy handed?
God Bless,
Brandon
MadAngler1
06-13-20, 13:28
The upper is at Knight’s now. We’ll see what happens
FYI, the A5 + Daniel Defense mid-length shoots softer than the Knight’s mod 2 suppressed and unsuppressed. Perhaps my barrel’s port is too large. We’ll see
MadAngler1
06-18-20, 18:08
Knight’s is shipping the upper back. They say the gas system is fine and there are no issues. They did replace the sling studs though for my upper. I will try it again and probably sell it. My DD upper + A5 lower shoots better anyway.
MadAngler1
06-28-20, 14:56
I got the upper back via UPS. Will try it again this coming week.
I got the upper back via UPS. Will try it again this coming week.
Thank you. Please let us know if you see any difference. I'm curious.
My DD upper + A5 lower shoots better anyway.
Please define “shoots better”
Tnx
MadAngler1
07-08-20, 19:30
Please define “shoots better”
Tnx
Smoother cycling, less felt recoil suppressed and unsuppressed. Less gas to the face suppressed. I have not accuracy tested either upper at 100 yards with match grade ammo, but both appear to do well with M855.
I shot the upper over the weekend and the results were the same. I’m going to try the Knight’s upper on my A5 lower next. Otherwise I’ll sell it. I like Knight’s controls. One thought it to install an A5 buffer tube on the Knight’s lower. Might be the best of both worlds.
Smoother cycling, less felt recoil suppressed and unsuppressed. Less gas to the face suppressed. I have not accuracy tested either upper at 100 yards with match grade ammo, but both appear to do well with M855.
I shot the upper over the weekend and the results were the same. I’m going to try the Knight’s upper on my A5 lower next. Otherwise I’ll sell it. I like Knight’s controls. One thought it to install an A5 buffer tube on the Knight’s lower. Might be the best of both worlds.
Thanks for the write up and responses in the thread. Very interesting, and appreciated.
You have a lot of variables at play here (gas system, buffers, springs, cans). Have you considered that the can itself might be the culprit vs the upper? Maybe swap muzzle devices and cans, try it on both lowers and see if the issue persists.
MadAngler1
07-17-20, 18:03
Well, it worked. Still not as nice as the DD upper. Using the BCM A5 lower with a A5HO buffer + Sprinco Green rifle spring, it worked unsuppressed and suppressed. With the Radian SD charging handle, the gas was tolerable, but still not as nice as the DD upper.
I’m guessing it’s all about (1) the gas port size) and (2) the Knight’s can has more blowback than the Surefire 556 SOCOM 2. It’s either both or one of those factors. Knight’s said “nothing was wrong” with the upper in terms of gas. They did not want me to ship my can for testing either when I asked the customer service rep. I’m guessing they jacked the port size up slightly larger so the rifle runs unsuppressed with crappy .223 pressure ammo.
I guess I’ll keep the SR-15, assuming I can put an A5 buffer tube on it. Anyone know this is possible? is the castle nut proprietary? Haven’t had a chance to look yet tonight.
Edited to add: If it wasn’t for the political climate and lack of supply, I’d probably sell it. I’m very interested in the Barrett Rec 7 piston upper with its adjustable gas block. I had an opportunity to buy a SCAR 16s new in box for $2200 in 2017. I’m kicking myself big time for not jumping on that. My SCAR-17 runs great suppressed with the SOCOM 762 can; I just wish they made a damn shoulder on the barrel so you wouldn’t have to use a special washer/ring.
That’s so crazy. Tons of people say that the KAC has less back pressure.
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TL;DR
Have you tried a standard spring instead of the SpringCo green?
MadAngler1
07-19-20, 21:30
TL;DR
Have you tried a standard spring instead of the SpringCo green?
I’ve tried both.
For the DD upper, sprinco green + A5H1 works best for me.
The knight’s ran fine with an A5H0 and either spring. Seems to be slightly less blow back with the Green spring
I’ve tried both.
For the DD upper, sprinco green + A5H1 works best for me.
The knight’s ran fine with an A5H0 and either spring. Seems to be slightly less blow back with the Green spring
How is your brass ejecting on the SR15 unsuppressed? My 14.5 mod 2 with Vltor A5 H2 ejects at 1 o’clock which leads me to believe it’s over gas.
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MadAngler1
08-27-20, 20:30
How is your brass ejecting on the SR15 unsuppressed? My 14.5 mod 2 with Vltor A5 H2 ejects at 1 o’clock which leads me to believe it’s over gas.
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Sorry for the late reply.
It will be 1 o’clock with the std carbine buffer and spring Knight’s ships with the gun unsuppressed. I can tune it to a H2 with std spring or Sprinco blue + H/H1.5 buffer to make it run unsuppressed reliably. I get the best of both worlds (with and without a can) with a Sprinco blue + H1.5 buffer (Slash heavy buffer with custom weights).
Running the upper on an A5 lower helps a little bit but not much. My DD 16” upper spanks it.
MadAngler1
09-06-20, 18:37
I replaced the forward assist with an SSS gas vent. It helped a little bit. Using a H buffer and sprinco blue spring (carbine length buffer) I was able to put 150 rounds today through the system at an indoor range (again all 55 gr M193 IMI). No malfunctions.
I’m going to keep the gun since it’s
tolerable. It is not as good as an A5 with the DD 16” mid-length and SOCOM 556 can. However, I will play with a few more things........like the Surefire OBC (of course I will put the Knight’s bolt in). I tried a Bootleg carrier.....will not work.
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