Brake vs. Bare Muzzle vs. Flash Hider...it matters.

[Failure2Stop]

In what ways? I am not arguing, but I am buying an SR25, and still trying to wrap my head around why it's not just an "M4 heavy"

Recoil, gas expansion effect on attached devices, projectile-air-shock, and pure volume of gas are all significantly different.
Just because something works on 5.56 with regard to muzzle devices doesn't mean it will do the same thing on .308.

[09stanggt]

I've heard similar claims before too. But in my own experiments using a PWS PRC on my 308 and a PWS FSC556, I haven't been able to quantify any difference in accuracy. Granted, mine is a very limited sample size.

I too went with a PWS PRC based on other's results. I've done as well as 1/2" with it on an 18" rock creek on Armalite receiver.

Sent from my SM-G920P using Tapatalk

[opngrnd]

Attachment 45597
Attachment 45598
Rifle:18" Sionics bbl, gas block, gas tube, NP3 bcg, ALG 15" V1 EMR, BCM Ambi CH, SSA-E, Vltor A5 RE w/A5H3, Springco Green spring.

Weather: 80ish degrees, 5 mph wind left to right
Load: Wolf SRM/23.4gr XBR 8208/77gr TMK
Not my best accuracy load, but I seem to average 1.5 MOA over 500 rounds of it, although I'm not a good precision shooter.

Shot sequence: Bottom right, bottom left, middle, top right, top left.

Procedure: I fired 10-shot groups with 4 minutes between groups. I rested the front on a bag, and put a small bag underneath the stock that I would adjust as needed. Not really a fine tuned set up. After the five groups with the A2/ crush washer on that had been there since I built the upper, (approx 800 rounds) I replaced the A2 with the Vortex flash hider using Aeroshell 33ms on the threads and handtightened three times. I set it in airconditioning for 10 minutes, fired ten rounds of plinking ammo, set the timer for four minutes, and proceeded to follow the original firing sequence on the second target.

Nothing particularly remarkable, but I haven't been beyond 100 with it yet. The approx 4" shift in POI make me wonder if barrel harmonics will be affected. If you can't read my writing, the final groups with A2 were 1.59 if you minus the called flier from the middle group, 1.76 if you don't, and 1.56 with the Vortex flash hider.

Edit: no idea why, but the pictures shifted 90 degrees counter-clockwise...

[georgeib]

Attachment 45597
Attachment 45598
Rifle:18" Sionics bbl, gas block, gas tube, NP3 bcg, ALG 15" V1 EMR, BCM Ambi CH, SSA-E, Vltor A5 RE w/A5H3, Springco Green spring.

Weather: 80ish degrees, 5 mph wind left to right
Load: Wolf SRM/23.4gr XBR 8208/77gr TMK
Not my best accuracy load, but I seem to average 1.5 MOA over 500 rounds of it, although I'm not a good precision shooter.

Shot sequence: Bottom right, bottom left, middle, top right, top left.

Procedure: I fired 10-shot groups with 4 minutes between groups. I rested the front on a bag, and put a small bag underneath the stock that I would adjust as needed. Not really a fine tuned set up. After the five groups with the A2/ crush washer on that had been there since I built the upper, (approx 800 rounds) I replaced the A2 with the Vortex flash hider using Aeroshell 33ms on the threads and handtightened three times. I set it in airconditioning for 10 minutes, fired ten rounds of plinking ammo, set the timer for four minutes, and proceeded to follow the original firing sequence on the second target.

Nothing particularly remarkable, but I haven't been beyond 100 with it yet. The approx 4" shift in POI make me wonder if barrel harmonics will be affected. If you can't read my writing, the final groups with A2 were 1.59 if you minus the called flier from the middle group, 1.76 if you don't, and 1.56 with the Vortex flash hider.

Edit: no idea why, but the pictures shifted 90 degrees counter-clockwise...

Nice.

So if I'm reading everything correctly, it looks like there's a shift in POI, but no statistically significant change in accuracy between the A2 and the Smith Vortex. Is that right?

[opngrnd]

Nice.

So if I'm reading everything correctly, it looks like there's a shift in POI, but no statistically significant change in accuracy between the A2 and the Smith Vortex. Is that right?

In my case, correct. I didn't see anything telling, but I don't hold the tightest groups. Perhaps a 1/2 MOA shooter would see a repeatable difference.

[DevL]

I don't see anything in the groups but noise. The gun is so inaccurate, you can't make any claims the muzzle device is the issue. Show me gun with all holes touching and change muzzle devices and we can talk. Also the idea of a 1/2 MOA shooter discussing what is causing inaccuracy is laughable to me. I consider myself a 1/10 MOA shooter, and that is on the outter limits of what I would consider as a good enough shooter to evaluate what metrics cause what anomalies.

This problem seems fairly common in AR centric shooters who are not familiar with what an accurate shooter or accurate gun really is. A half MOA 5 shot 100 yard gun is really on the outter edge of being "accurate" since accuracy will degrade at range. AND when discussing accuracy, it should be .5 MOA for most of its groups, not the best of the day.

The "noise" in those groups is just too extreme to draw any conclusions from a few groups. If all the groups were well under an inch and only went to a full inch 2 of 5 groups with a brake, it would be interesting. In my experience, a brake is a sub .1 MOA difference if it exists at all. While I have heard of excessive torque causing accuracy issues, in my own testing intentionally torquing muzzle devices up to 50 ft/lbs caused no issues. I found it shocking after years of reading forums tell me it would ruin accuracy.

[tpe187]

Well, I think its an interesting thing to look at. I've heard that FHs are more accurate the MBs. The problem I have is that I can't really tell a difference with the two targets. You use two different target types. One is circles, one is diamonds. I personally shoot better on diamonds. The grid system is different between the two and you don't have any measurements on the target. Also, I found that shooting the SR25 I had to really look at how I shot it compared to precision 5.56 or bolt guns. I have found the 7.62 AR is one of the harder weapons to consistently shoot well, something that we may be seeing with groups on two different days.

[waveslayer]

I doubt the brake or no brake has anything to do with your groups.

I would like to see the load data for this precision ammo. In addition, wad the last shot on an empty mag?

I know of situations where the noise increase mentally sacred people, causing them to flinch. Etc...

my wife thinks I only have 3 guns

[Gödel]

Is there any chance these effects could be do to a collet effect on the crown? It would be interesting to put the device on with only loctite (which I realize isn't going to work if the barrel gets at all warm). But it would be a way to isolate torque from gas flow effects.

[VelveteenMole]

I can't help but think it would take somehow controlling for barrel harmonics to actually isolate the flow patterns of a brake or comp as an accuracy culprit. If your gun is grouping well with a load, it might have found a node, and changing that timing would be likely to result in fliers.

I would also think that a symmetrical break would be incapable of introducing a non-repeatable or destabilizing aerodynamic deflection. After all, suppressors act much like a brake for the purposes of the bullet's microenvironment as it is overtaken by uncorked gas-flow, and they are often credited for accuracy increases (no doubt partially due to dampening or delaying large oscillations at the muzzle), so I would expect that a truly symmetrical brake design at least would cause no aerodynamic disruption.