Q Boombox In Subsonic 8.6 Blackout - Anyone With Accuracy Data?

8.6 Blackout???

100 yd and 6.5tw Mos-Tek
Early in load development.
I realize it doesn’t answer your question re Q. These are supers.
Also, doesn’t make any sense to shoot subsonic to 300 yd for accuracy honestly. Maybe for fun but realistically no practical application sub.

SP10

^^^ what he said
A 300gr SMK would still be around 960-1000 fps w/ 840ish energy at 300 but it’s dropping almost 10 ft. A lot can happen with a potentially unstable bullet in that line of flight.

Kevin B in interviews re: 8.6 has been saying a super fast twist is needed for optimal accuracy (as he calls it "dispersion") like what they use 1 in 4 or 5 if I recall

Milirad said:

Does anyone have direct experience with or a reliable source for Boombox subsonic accuracy in 8.6 Blackout at a range of 300 yards +/-?

Subsonic accuracy of 1.5 MOA at 300 yards is my desired spec for reliable subsonic kills on coyote and hogs. I've been waiting for a few years for a subsonic AR 8.6/338 option that will repeatably meet this performance level with high quality factory ammo, preferably with a reasonably high BC bullet to buck wind. I was encouraged when Q announced that the Boombox would be 1 MOA or better with factory subsonic ammo, but I can't find any trusted range test results on the boombox with subsonic ammo.

Also, anyone have experience or reliable accuracy data on an AR that achieves this level of performance with factory 338 ARC 307 Sub-X?

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I'll tell you for sure that claims of any subsonic center-fire cartridge being 1 MOA consistently are false. 300BLK, 8.6BLK, 45-70, you name it, it ain't happening. Now that being said, with velocity in the 900-950fps range you could reasonably expect 2 MOA. I have managed 2 MOA over a 20 shot group with Gorilla 342gr bullets, and only around 6 SD so I'd be comfortable shooting that at 300.

AustinP69 said:

Kevin B in interviews re: 8.6 has been saying a super fast twist is needed for optimal accuracy (as he calls it "dispersion") like what they use 1 in 4 or 5 if I recall

Click to expand...

1:3 on the Q barrels

I chased my tail loading subsonic 300 blackouts with that same goal. What I found is that low development is extremely finicky. So many more factors come into play than supersonic ammo. You are dealing with so much less powder and much more case capacity.

I had a 16-in Wilson 1-8 barrel that printed subsonic clover leafs at 50yds and held 1MOA to 100yds. I could pretty reliably hit a 10-in plate at 300 yd. However, I could never get the SD tight enough to avoid vertical dispersion.

Then I cut it down to an 8 or 9" barrel and found that the groups starting opening up. I think you really need at least one revolution inside of the barrel to stabilize a heavier subsonic bullet. For example, an 8" barrel with almost 2" of chamber, needs a 1:5 or 1:6 twist.

I didn't make it far with the load development after I chopped it. Instead, I snagged a Noveske 12" barrel with a 1:7. Low and behold, groups tightened up. It held just over 1MOA with SD in the low teens using N120 and 220SMK bullets.

Take this all with a grain of salt as it's not the 8.6 you are discussing. Just that if you are getting 1.5 MOA and can get single digit SDs with handloads, I'd call that a win here.