18" SS BCA barrel and BCG range report

[opticsguy]

This was an upper I got for pig hunting at a gun show. I went to the range to compare SST ammo to Black and sight in the $70 AIM 4x scope. Between the gusty wind and not getting a stable rest using the sandbags I had, my groups weren't great, but I was able to get smaller groups with the SST ammo. The barrel probably had 20 rounds through it by this point.

I was using the all-black lower with a CMC single stage match trigger to start

grendels.jpg

I gave up on the sandbags and got the bipod out and held the gun snugly and fired 3 shots at a new target at 50 yd. Those are the ones on the left. A nice .5 MOA group. Then I switched to the other lower with a mil-spec trigger and I had very little luck with that (right target). I believe, but am not sure, that I used SST ammo for the group on the left. It's the nicest group I've shot so I'm not adjusting the scope anymore, and I'm definitely upgrading the trigger on the other lower.
grendel group.jpg

[armedferret]

Looks like a 1 MOA group to me if it's at 50 yards. Either way that'll do nicely.

[Lemonaid]

Wishing best of success and luck, but don't be surprised or dismayed if at 100 yards or more the groups open up to weird sizes. My initial 25 yard groups were one small hole for 6 rounds but opened up to over 2 inches at 100.
Others have encountered this phenomena and I don't know why. I suspect it may have to do with the long 6.5 bullets and when they "go to sleep" (fully stabilize). In my case I am convinced that the BCA flash hider was hindering best accuracy and groups got better when I replaced it with a thread protector.
The fun is in the hunt for the best load!

[CaptnC]

In my case I am convinced that the BCA flash hider was hindering best accuracy and groups got better when I replaced it with a thread protector.
The fun is in the hunt for the best load!

That's an interesting thought...I keep thinking it has something to do with their uppers. All my BCA purchases have been barrels only, so I'm not dealing with their assembling the upper. I did buy the right hand side charge and really like it! But again, I dI'd the assembling after the purchase.

I'd like to hear more about what you found wrong the the Flash hider.

[Lemonaid]

Thick carbon buildup on crown face and inside the flash hider. When I went with just a thread protector it looks like gas pressure went down as my cases have that sooty look (may be wrong on that). Same starting load before did not do that with the flash hider on.
My theory is that the gas going through the flash hider is disturbing the bullet after it exits the barrel more that it dose with out it on.
Also, its another variable in the system.
Same load (Accurate 2200 and Speer 90 tnt) shot tighter groups with out the flash hider.
Your results may vary!

[CaptnC]

Very interesting. I put big .30 caliber, three chamber breaks on my BCA 6.5 Grendel barreled rifles. So I don't have anything like that going on. My 7.62x39 has a flash hider, but it's for a 9mm or 45. The hole is huge. Most likely not doing much flash hiding! LOL

[A5BLASTER]

Thick carbon buildup on crown face and inside the flash hider. When I went with just a thread protector it looks like gas pressure went down as my cases have that sooty look (may be wrong on that). Same starting load before did not do that with the flash hider on.
My theory is that the gas going through the flash hider is disturbing the bullet after it exits the barrel more that it dose with out it on.
Also, its another variable in the system.
Same load (Accurate 2200 and Speer 90 tnt) shot tighter groups with out the flash hider.
Your results may vary!

The flash hider idea is close but it's most likely due to barrel harmonics and how the flash hider was torqued on.

That's why the thread protector isn't effecting your groups. It's not torqued onto the end of the barrel. Soon as you induce torque too attach something at the end it effects barrel harmonics.

This is why I use the accuwasher system and the no torque approach to installing muzzle devices.