Pulling my hair out.

[dustinm]

Long time shooter, first time builder.

I am building a 300 Blackout. Trying to decide on a barrel. It seems like every time I decide on something I read a post that someone else contradicts it. The two items I cannot decide on are gas block length and twist.

Originally I was going to buy a 16" 1x8.5 twist with a adjustable pistol length gas block, however many forums say carbon length will work just fine and buy a 1x11.

So, if anyone has hands on experience with a suppressed 300 blackout I'm all ears.

Thank you.

Read More

 

[KillerBD]

FWIW: The twist rate on my Bulgy 7.62x39 AK is 1x9.44, which from my layman's research the .300 Blackout appears to have quite similar ballistics. Though not identical of course, but I figured I would toss in my 2 cents. Hopefully a cooler/smarter .300 Blackout ninja-operator will show up and give you the scoop

 

[dustinm]

KillerBD-Thanks for the info. I am more concerned with the gas system than twist. I'm worried if I bought a 16" barrel with a pistol length gas port and a non-adjustable gas block that the pressure would be too high when shooting normal ammo.

 

[Nwcid]

What grain/length bullet do you plan on shooting, that will make the most difference.

The .300 Whisper, parent to the BLK was meant specifically to be a hard hitting subsonic round using every standard part on the AR except the barrel.

If you plan on shooting heavy/long subsonic bullets a 1:11 will NOT stabilize them.

I had a Whisper barrel built by Lilja with a carbine length gas port with a PRI low pro block, 16" long with a 1:8 twist. I only shoot mine with 220gr + bullets, subsonic with a silencer on.

 

[KalamaMark]

I'd go 1:7 or 1:8 to stabilize subs, and carbine length gas port.

 

[Nwcid]

I'd go 1:7 or 1:8 to stabilize subs, and carbine length gas port.

I can not easily find the information right now about twist rate. Since I had a custom barrel built I had my choice of twist. When I was researching it SSK had found that 1:7" made the bullet very stable which was good. They found the 1:8" to be better as the bullet would stay stable in flight but was easily upset when coming into contact with an object causing more damage. Of course that is the very short paraphrased version, but it is why I went 1:8"

 

[spectra]

Lets just say buy a Noveske barrel and call it good You might pay a little more for it but in the end it will be worth it. Noveske builds all there barrels based off a suppressor being on it. I have a 16 with a pistol gas system and waiting on a 8.5 with a pinned can to be sent to my local dealer. Next build is going to be the 10.5 in a pistol version. Maybe the SBR bill will make it through.....

 

[KalamaMark]

A Noveske with a Switchblock would be very, very nice..

 

[PotshotJim]

I have a pistol gas 16" ss NEMO .300BLK barrel with 1:7 twist that runs 110 - 150 grain supers and 200 - 220 grain subs without any malfunctions unsuppressed. My can is still in jail, so I can't report on suppressed operation.
According to AAC, if the weapon functions correctly with subs unsuppressed it will function correctly with the suppressor mounted.

The reasons I chose a pistol gas 16" (based on info available at the time):
Better reliability with sub's
Better range with supers
Longer sight radius with iron sights
The option to have the barrel shortened later if I want to.

So far all this has been as good or better than I expected.

Like spectra, the next build will be a 10.5".

 

[dustinm]

Thanks for all the replies! I plan on shooting a 180-220 grain bullet. I found blackhole weaponry sells very nice barrels and hope to do business with a local company. 1x8 is what I am leaning to.

PotshotJim-With your setup, is your gas block adjustable? Any problems shooting subs then switching to supers with the pistol length block?

 

[PotshotJim]

No adjustable gas block.
No problems with ammo cycling the action.
The best operational test for sub's that I've seen is that the bolt holds open after the last round is fired without a suppressor. This means that the bolt is fully cycling and not short stroking. All my sub loads do this successfully.
To be clear, I build my own ammo. I can't speak for results with brands x,y, or z because I've never fired them.

 

[dustinm]

Can you share your sub load with me? I have trailboss and bullets, but haven't had time to research the best combination.

 

[PotshotJim]

The Lee load data works fine for me. Start with that.