Suppressors Long range subsonic 300BLK load?

[phlegm]

Shooting my AAC-SD in 300BLK is a hoot. I'm still working up some loads after liberating some factory loaded Hornady 208s from their brass.

So far, factory ammo has made it a 1 minute gun to 200 yards. Hitting a 10" steel at 300 is about 75%. At 400, the thing goes crazy. I can't get within a foot of a man-sized target.

I do have some 240 SMKs to load up, and I'm hoping they do well (my wallet isn't). Does anyone have any experience with an a subsonic load that is accurate past 300 yards?

 

[bunsen27]

Trying to get accuracy at 300yds with subsonic .300Blk is pushing expectations a little bit IMO. I just got mine set up, but I've shot a lot of 22LR at distance and it reminds a lot of that platform. Past a certain distance, unless it's dead calm, you are just wasting ammo.

 

[Yasherka]

I shoot Hornady 225gr match rounds on top of 8.9gr of Vihtavuori N110. Last Sunday I was shooting at a half-scale steel fox target at 355 yards and hitting it nearly every time... in excess of 85%. However, I am shooting a Howa 1500 bolt action, not a semi, so the results may be different than what you get.

What is your twist rate? Also, have you chrono'ed your loads?

 

[ironshooter]

In my opinion, 8 twist is marginal for shooting the heavies subsonic in 300BLK. AAC really dropped the ball by not going with AT LEAST a 7 twist. Preferably a 6.5 twist.

 

[itieknots7]

In my opinion, 8 twist is marginal for shooting the heavies subsonic in 300BLK. AAC really dropped the ball by not going with AT LEAST a 7 twist. Preferably a 6.5 twist.

Both my AAC barrels are 1/7 Twist (16 and 9" AR factory AAC uppers). 1/8 was first used but later changed IIRC.

 

[phlegm]

I shoot Hornady 225gr match rounds on top of 8.9gr of Vihtavuori N110. Last Sunday I was shooting at a half-scale steel fox target at 355 yards and hitting it nearly every time... in excess of 85%. However, I am shooting a Howa 1500 bolt action, not a semi, so the results may be different than what you get.

What is your twist rate? Also, have you chrono'ed your loads?

I do have a bolt gun. It's got a 1/7 5R barrel.

I haven't sent anything over a chronograph. The factory sub loads do have an audible difference among them, which goes along with the 300's reputation for having higher standard deviations and extreme spreads than some other cartridges.

 

[Yasherka]

I do have a bolt gun. It's got a 1/7 5R barrel.

I haven't sent anything over a chronograph. The factory sub loads do have an audible difference among them, which goes along with the 300's reputation for having higher standard deviations and extreme spreads than some other cartridges.

I have fired about 200 rounds of factory Remington subs through mine and they were horrible. SD's were all over the place and the powder was filthy. Currently my load is giving me mid-to-high-teen SD's, but I'm trying to improve that (I suspect the brass capacity may be the culprit as I hand weigh each charge).

 

[bohem]

Likely the barrel twist is too slow and you're getting growth of the slow arm in the epicyclic motion where the "wobble" is no longer containable.
The solution is to either buy a faster twist barrel or go to a shorter projectile.

I would suggest that you drop the 240's and go to a shorter bullet, or a round nose heavy. I strongly suspect this will correct the issue for you.
Remember, at the speeds we're talking, BC's measured at supersonic velocities are largely inaccurate and significantly less important.

I've shot 210's from an 8.5tw at subsonic speeds without issue to 500yd on torso plates.

 

[rjacobs]

Try some 208g AMAX. Ive made hits on a torso sized plate at ~400 yards with an Aimpoint T1, but I was holding probably 15 feet high.

 

[BravoSix]

This thread is very relevant to my interests. Tomorrow I should get the final pieces needed to finish my 300 upper. My sole intent is shooting subsonic as far as the travel in my optic will allow. I am interested in reading about others' experiences.

 

[RHunter]

I have had awesome luck to 400 using those 200 grain subsonic bullets that Lapua makes out of a 1/8 twist barrel. Little pricy but they fly great.

I recently purchased 600 from Bullets.com, first I have seen of them in over a year if you want to give them a try... Off hand I think my load was 9.8 grains of aa1680.