Was considering building a 300AAC with a 10.5 barrel using an Aero upper, lower, and atlas handguard. I don’t currently have anything else in this caliber but wanted to do a pistol length AR. Then I come across this in an email.

http://palmettostatearmory.com/psa-7-5- ... 3a00+Email


Thoughts? Any pros or cons with this barrel length?

Figured I can try this one out and eventually build one to my liking if I like it or want to do something different.

Don’t have a suppressor yet, but something I will eventually do

If you plan on running a suppressor check to see what it's rated to.

I have a Recce7 and it's 'rated' down to 8" for 300BLK although I'm sure it would be fine on a 7.5" with subs.

I currently have it on a 8.5" upper and it ends up being a little shorter than a standard 16" upper.

My son and Daughter In Law just purchased 2 complete PSA uppers in 5.56......Neither one of them operate more than a single shot. Swapped one of my uppers on their lowers to make sure it wasn't an issue with lowers....Nope ran perfectly. Not sure what the problem is but it is pretty sad that 2 brand new "factory assembled" uppers do not operate.....just a for what it is worth.

This^^^^

Also, my dad has their 8", and it runs like a top. No problems on an Anderson lower with PSA parts kit.

I have 1n 11.5" PSA upper in .223/5.56 and no problems.

just don't mistake your rounds.

ps ill take your uppers and see whats wrong. could be gas block not on right is all

I have an 8" 300BLK upper (not from PSA) and mine runs well with my subsonic loads. If you want to use a suppressor and subsonic ammo, then I think the shorter barrels are probably better because they will keep the velocity down (i.e., subsonic) without forcing you to drop the powder charge too low.

Another thought is that if you're going to run a suppressor, you need to make sure you can attach it (thank you, Captain Obvious, haha). So if the end of the muzzle threads are inside the handguard, and the handguard is too small in diameter to "tuck" your suppressor, then you're hosed. I'm guessing from the PSA photo that this is the case here, and you wouldn't be able to attach a suppressor without more work.

May consider going 223/5.56 just to keep some uniformity. But then I’ll have the nagging feeling of still wanting a 300AAC on hand.

also make sure its pistol gas. I've heard they can be finicky.

Don't let this be you

Factory loads out of a 16" bbl are still subsonic.

Have you checked the gas block to make sure the rifle is cycling correctly? Might be worth a quick look.

Does anyone with a 7.5" or 8" barrel have issues with incomplete powder burn on .300 AAC BLK subs? I know that's an issue with short 5.56 barrels, but not sure if it would be different for .300 considering the loads are quite different.

Do I ever. I was considering starting a thread on it. I get a lot of powder all over the inside of the ARs. Yet, I lose velocity if I back off the charge...wtf?

I read that 300 BO was designed for a 10.5-11 inch barrels. Might be why people are getting unburned powder in the shorter 7.5-8 inch barrels.

What powder are you using?

Probably need something that burns faster. All 300BLK that I've seen use pistol length gas systems. Not a lot of time to burn everything up.