300 blk and gas system optimization

[MistWolf]

May I ask why? What are the benefits, etc? Why not mid or carbine length? Thanks

If you go back and read the thread from the beginning, you'll see why not a middy

[Clint]

If you go back and read the thread from the beginning, you'll see why not a middy

This.

The 5.56 has a longer pressure curve than 6.8, which is longer than 300BLK.

The faster the pressure drops off, the larger the gas port needs to be.

If the gas port needs to be bigger than the max (.125), the gas system needs to be shortened to get enough gas drive.

[Civil]

If you go back and read the thread from the beginning, you'll see why not a middy

I've read it from the beginning but man you guys really get into the details. Just tell something around the lines of, "small boom go short, big boom go long" or something like that.

This.

The 5.56 has a longer pressure curve than 6.8, which is longer than 300BLK.

The faster the pressure drops off, the larger the gas port needs to be.

If the gas port needs to be bigger than the max (.125), the gas system needs to be shortened to get enough gas drive.

So guessing mid is too long due to the bullet taking up most of the brass' room. Say I want to shoot up to but not limited to 500-600 yds with super, is carbine length capable?

Judging from Onyx Z:

16" carbine gas 300BLK here. I have not had a single hiccup in this rifle. Vltor A5 kit should be here Friday, it should be just about perfect then.

I wouldn't go Pistol gas unless it is to be suppressed or a SBR/Pistol.

...seems like the way to go. And Onyx what is the gas port size you have for your upper?

[Onyx Z]

So guessing mid is too long due to the bullet taking up most of the brass' room. Say I want to shoot up to but not limited to 500-600 yds with super, is carbine length capable?

Judging from Onyx Z:


...seems like the way to go. And Onyx what is the gas port size you have for your upper?

No idea on the gas port size, but I can check when I get home. It's a 16" DD 300BLK S2W barrel.

Generally, gas length has nothing to do with effective range of a rifle. It only has to do with the action, which you feel as recoil.

If you are looking for 500+ yds with a .30 cal bullet, I would definitely turn my attention to a larger caliber cartridge, not a 300BLK. There just isn't enough room in the case for the powder to get the bullet travelling at proper the velocity.

[Civil]

No idea on the gas port size, but I can check when I get home. It's a 16" DD 300BLK S2W barrel.

Generally, gas length has nothing to do with effective range of a rifle. It only has to do with the action, which you feel as recoil.

If you are looking for 500+ yds with a .30 cal bullet, I would definitely turn my attention to a larger caliber cartridge, not a 300BLK. There just isn't enough room in the case for the powder to get the bullet travelling at proper the velocity.

Thanks, I'll hold you to that. I'm planning on getting an upper from Arsenal Democracy, and when I get it, want to zero in at 300 yds; 500-600 yds is just for kicks in case I feel like or have to shoot that far with 300blk. Also, a barrel change and maybe buffer group will do fine if I want to go back to 556.

[kR-15]

May I ask why? What are the benefits, etc? Why not mid or carbine length? Thanks

If you roll your own ammo and want to shoot subsonic rounds there are some powders that will cycle in a pistol length gas system but not a longer system.

My experience so far has been good with a carbine length gas system though- there is a decent array of powders that are reliable in a carbine for subsonics.

[duece71]

If you roll your own ammo and want to shoot subsonic rounds there are some powders that will cycle in a pistol length gas system but not a longer system.

My experience so far has been good with a carbine length gas system though- there is a decent array of powders that are reliable in a carbine for subsonics.

This is nice to know, if I get into 300blk, I would definitely want to roll my own.

[Onyx Z]

Thanks, I'll hold you to that. I'm planning on getting an upper from Arsenal Democracy, and when I get it, want to zero in at 300 yds; 500-600 yds is just for kicks in case I feel like or have to shoot that far with 300blk. Also, a barrel change and maybe buffer group will do fine if I want to go back to 556.

My gas port is .118. I'm willing to bet DD tuned it to this size for the carbine gas.

[mic2377]

In terms of gas port for carbine gas, bigger is better. In fact, running a gas port at .125 seems to have no detrimental effect in terms of overgassing even with super ammo, and seems to significantly help reliability with subs. It is good to hear that DD made the gas port fairly large on their 16" barrel.

Personally, given the 300 BLK's intended use, I would personally always choose a pistol gas even if I was going with a 16" barrel. This is for maximum reliability with subs and more latitude to play with powders. Also, if you are zeroing at 300 yds, you are missing the point of this cartridge. From my calcs, a 300 yd zero puts you nearly a foot over POA at 150 yds.

[hotrodder636]

Midlength gas will not work at all.

Your choices are carbine or pistol. Either one works fine, as long as the maker picked the correct has port size.

I have a LMT MRP barrel in 300BLK from LMT and it has a pistol length gas system. Works just fine so far.