School me on Suppressed 300BLK Ballistics

[Hollywood Ball]

Admittedly I don't know a lot about ballistics, grains, twists, etc..

I took my .300BLK AR pistol out today to sight in the Vortex Spitfire II. Rounds were on target and the optic was dialing in OK, but closer inspection of the target revealed some serious tumbling. Long, narrow holes on target that made it apparent the bullet it was going through completely sideways.

So please help me understand what's going on.

9.5" barrel, marked "1/9.5 T 125gr"
Gemtech 7.62 HVT
Ammo1 - Sig Sauer Elite Performance "match grade" subsonic 220 gr.
Ammo 2 - SilencerCo Harvester subsonic 220 gr. sierra matchkind

Ammo 1 was the first used to sight things in and was the worst. Bullet holes with Ammo 2 were much cleaner, but still appeared to have a little bit of tumble.

So, what says the forum?

 

[Speed3]

1:9.5 is your twist rate in the barrel. Sounds like the bullet isnt stabilized enough and they are tumbling.

My 300blk barrel is 1:7 twist and I haven't seen a problem yet. I would assume 1:9.5 twist rate isn't fast enough for subs. Try some 208 gr subs maybe???

I would NOT shoot those suppressed through that can until you find a bullet that will stabilize, you are risking a baffle strike and ruining your can.

 

[Tconfo]

If definatley keyholing DO NOT USE THAT SUPRESSOR. The bullet isn't stabilized enough. A blackout barrel shooting suppressed loads or longer projectiles definatley needs a 1:8 or a 1:7 twist. If it is unstable at the target I wouldn't trust it at my muzzle;definatley not in my can. Swap the barrel, everything will pan out

 

[Hollywood Ball]

Yea, that's what I'm worried about, and why I'm asking.

 

[Hollywood Ball]

If definatley keyholing DO NOT USE THAT SUPRESSOR. The bullet isn't stabilized enough. A blackout barrel shooting suppressed loads or longer projectiles definatley needs a 1:8 or a 1:7 twist. If it is unstable at the target I wouldn't trust it at my muzzle;definatley not in my can. Swap the barrel, everything will pan out

Cool. Thanks.

 

[Hollywood Ball]

1:9.5 is your twist rate in the barrel. Sounds like the bullet isnt stabilized enough and they are tumbling.

My 300blk barrel is 1:7 twist and I haven't seen a problem yet. I would assume 1:9.5 twist rate isn't fast enough for subs. Try some 208 gr subs maybe???

I would NOT shoot those suppressed through that can until you find a bullet that will stabilize, you are risking a baffle strike and ruining your can.

If definatley keyholing DO NOT USE THAT SUPRESSOR. The bullet isn't stabilized enough. A blackout barrel shooting suppressed loads or longer projectiles definatley needs a 1:8 or a 1:7 twist. If it is unstable at the target I wouldn't trust it at my muzzle;definatley not in my can. Swap the barrel, everything will pan out

Sounds like I... wait for it... dodged a bullet.

 

[outrider58]

Search for lighter(shorter bullets) in sub-sonics like a 208 gn. A-Max. They will stabilize easier.

 

[Hollywood Ball]

So, my Monday morning Google-fu is telling me that this problem isn't all that uncommon...

 

[Speed3]

So, my Monday morning Google-fu is telling me that this problem isn't all that uncommon...

With a slower twist barrel, probably not.

 

[Semper Noctem]

I wouldn't feel comfortable shooting subs through my can with a 1/9.5 twist. 1/7 for the win.

 

[Hollywood Ball]

I contacted Gemtech about their thoughts on the issue and they're going to send me a couple of boxes of their 187gr subsonic to try with my current barrel, before I go about replacing it.

 

[Speed3]

I contacted Gemtech about their thoughts on the issue and they're going to send me a couple of boxes of their 187gr subsonic to try with my current barrel, before I go about replacing it.

That might work...probably on the line, I hope it works out for you.

 

[Hollywood Ball]

That might work...probably on the line, I hope it works out for you.

Hope so. I'll heed everyone's warning though and test fire without the can.

Props to Gemtech's customer service though. Definitely not their issue to solve, but they've gone above and beyond. Very cool of them.

With a 1-9 twist, you could try our 187gn 300BLK ammo. Not sure that will help but will be better than the heavier rounds.

As far as your HVT goes, keep an eye on your endcap for rubs or copper marks. This will be your first indication that something is contacting your HVT when the bullet passes through.


Please respond to this email with a good address, and I’ll send you 2 boxes of our 187gn to try out in that twist.



Any questions or concerns please let me know.

Joey Harris
Senior Technical & Customer Service

 

[Semper Noctem]

I contacted Gemtech about their thoughts on the issue and they're going to send me a couple of boxes of their 187gr subsonic to try with my current barrel, before I go about replacing it.

That might work...probably on the line, I hope it works out for you.

I've got a boat load of that ammo, and it is wicked accurate and quiet out of my 8.5 noveske. The only complaint I have with it is that the filler make the inside of my rifle look like it has lice. Cleans out fine, but the first time I shot it I was a bit taken back.

 

[Hollywood Ball]

Got the ammo today. This was shipped for FREE, no questions asked, on an issue that really isn't even Gemtech's problem.

Hoping it works with my twist. If it does I'll put in a healthy order for the outstanding customer service.


Sent from my iPhone using Tapatalk

 

[Semper Noctem]

Shothe some more of that this morning. Hope you like it. Again, don't be surprised when you open up your rifle to see corn meal type flecks of filler.

 

[Alphabrew]

Just wondering why they make barrels for 300BO that have a twist that makes subsonic rounds tumble? I would assume most folks shoot this round suppressed.

 

[outrider58]

Just wondering why they make barrels for 300BO that have a twist that makes subsonic rounds tumble? I would assume most folks shoot this round suppressed.

I don't have that answer, but gun originally was designed for cqb and tumbling is probably not an issue at shorter ranges. I don't know.

 

[jimbobborg]

Just wondering why they make barrels for 300BO that have a twist that makes subsonic rounds tumble? I would assume most folks shoot this round suppressed.

"9.5" barrel, marked "1/9.5 T 125gr"" Not meant for sub-sonics from this. Not a lot of people have suppressors (including me).

 

[Hollywood Ball]

"9.5" barrel, marked "1/9.5 T 125gr"" Not meant for sub-sonics from this. Not a lot of people have suppressors (including me).

Yea, I'm not holding my breath over this diff ammo. But I'll give it a shot. If it works, great, if not, I'll get the barrel with the 1-7 twist that I need and chalk it up to a lesson learned.