Wondering what expect from a new 8” Aero precision upper. Will I be able to run subsonic through it as well as hypersonic without a bunch of drama? I’d just as soon avoid adjustable gas block. I’d like to think I’m not the first one to encounter this.

Hypersonic? That’s Mach 5 or about 5500 ft/second at sea level. Pretty zippy for .300 blackout.

I have a PSA 300 blk, 8.5” barrel (I think) and fixed gas block. It has run 100% with both sub and super, suppressed and not. Has an H2 buffer as well. Very happy not to have needed an adjustable gas block, although the only way to know for sure is experiment with it.

quote:

Originally posted by Dwill104:
Hypersonic? That’s Mach 5 or about 5500 ft/second at sea level. Pretty zippy for .300 blackout.

ya know that didn’t sound right as I typed it but there it is I guess.

quote:

Originally posted by Chris Orndorff:
I have a PSA 300 blk, 8.5” barrel (I think) and fixed gas block. It has run 100% with both sub and super, suppressed and not. Has an H2 buffer as well. Very happy not to have needed an adjustable gas block, although the only way to know for sure is experiment with it.

Thats what I like to hear! It’ll rarely be unsuppressed, those short barrels are just too much for my ears. But I really want to go both ways on speed. Thanks

I also have an Aero 8" 300blk upper. It's the one with the S-One handguard.

I have shot both supersonic & subsonic, suppressed & without with no issues. I also use an H2 buffer. I do use charging handles that are supposed to help with the extra gas.

Geissele, Raptor SD, Griffin Armament, etc. Whichever is on sale.

I have an 11" 1:7 twist Wilson Combat 300 blk upper, fixed gas block, H2 buffer. I shoot suppressed all the time.

I have shot a number of types of factory ammo -- more supersonic than subsonic. I find subsonic accuracy to be disappointing, mainly from vertical stringing. Supersonic accuracy from quality rounds is good -- 110 to 125 grain loads with good bullets.

The only cycling issues I have experienced with factory ammo is blown primers. Fiocchi 125 SST and Sig 125 HPBT were the culprits. All other ammo cycled just fine.

quote:

Originally posted by fritz:


The only cycling issues I have experienced with factory ammo is blown primers. Fiocchi 125 SST and Sig 125 HPBT were the culprits. All other ammo cycled just fine.

Interesting, I picked up a box of the Fiocchi last Friday. I’ve been grabbing a bit of just about everything I can find, especially the subs, as I’ve heard plenty of accuracy issues.

Every barrel is different...every chamber is different...

My notes show 3 popped primers from what was likely 2 or 3 boxes of Fiocchi 125 SST. I didn't go into much detail -- but I vaguely recall the rifle jammed on 2 of those. No serious jams, easy to clear. It's unfortunate, as the ammo was pretty accurate -- 5 round groups of 1.37" to 1.80" at 100 yards. Vertical dispersions in breezy conditions for 5 rounds at 250 yards of 2.5" and 3.0". The ammo held an outstanding 2.75" of vertical at 370 yards.

The Sig 125 HPBT was serious jam-o-matic. 7 popped primers in 6-ish boxes. The primers got jammed in the action badly -- mortaring and/or bore cleaning rod to clear the jams. The Sig's best accuracy results were slightly better than the Fiocchi SST, however a few of the 250-400 yard groups had 2+ MOA WTF fliers. In all the firearms I've ever shot, with all the factory ammo I've ever shot, this Sig ammo absolutely ranks #1 for being the worst.

*****
All FMJ ammo in the 140-150 grain ballpark showed poor accuracy, being 2-4 MOA groups at 100 yards.

Subsonic ammo almost always showed minimal lateral dispersion at 50-100 yards, but quite often a lot of vertical dispersion. Mainly quality bullets -- SMK, Amax, Hornady Sub-X. Groups of 2-5 MOA at 100 yards. Vertical dispersion was generally 2-3 times that of horizontal dispersion, even in breezy conditions. I tried a few rounds at 200-250 yards, with vertical stringing of more than a foot. Saw a few keyhole strikes on targets, too.

My best accuracy was with quality bullets in the 110-125 grain ballpark. 125 SMK, 110 Vmax, 110 Vortex. I have a couple of buddies who compete in PRS rifle events who own 300 blk ARs. They see the same types of ammo results. I will eventually limit my ammo holdings to Aussie Outback (ADI) 125 SMK and Hornady 110 Vmax.

quote:

Originally posted by Chris Orndorff:
I have a PSA 300 blk, 8.5” barrel (I think) and fixed gas block. It has run 100% with both sub and super, suppressed and not. Has an H2 buffer as well. Very happy not to have needed an adjustable gas block, although the only way to know for sure is experiment with it.

I have a couple of PSA AR pistols with 8.5"and 10.5" barrels. I have been looking into suppressors but have been reluctant with concerns about performance and changes I may need to make to achieve reliability. Very interested in the make of suppressors that you have. Looking at flowthroughs. I am interested in your thoughts and experience on those. TX in advance.

SilencerCo Omega

Thank you for your prompt reply. I was looking at that one. So, just to verify, no modifications required to retain factory reliability? I need to look up H2 buffer. Is that stock or did you change it? Thanks again for bearing with my ignorance.

I would only run the heavier buffer if your gun appears over-gassed with the can on.

I have no issues with an off-the-shelf 8" aero upper, non-H buffer. Running a Rugged Radiant.

I think it's the 5.56 NATO guns have all the gas issues.

Thank you very much.

One of the characteristics of .308 bullets is that they stabilize well, so shooting them through short barrels isn't as much of a shock to the cartridge. But it is my understanding that .308 from a 10" or shorter barrel does take a faster twist to stabilize properly. So one might expect to find accuracy to be off because rifle twist isn't fast enough (1:5 comes to mind).

5.56 NATO, on the other hand, is a hot little round that goes fast and is marginally stable at speed. I don't even know of anyone who makes subsonic 5.56. I would suspect gas to be a much bigger issue with 5.56 than barrel twist. Plus proper propellant burn in a short barrel for a cartridge that expects a decent 14" barrel as minimum length might also be an issue - in speed, range, flash. Not having yet shot any of those other than short sessions with a friend's .300 BLK in an SBR, I can only speak theoretically, not practically.

Huh? 5.56 is not marginally stable in proper twist barrels. Atomic makes 5.56 subsonic (what use it is I have no idea). What is your point about gas? managing the gas situation in suppressed AR's is always an issue, but it in not related to twist. 10" or so 5.56 barrels are completely common when the user wants a short package and is willing to accept the tradeoffs, what is your point exactly?

quote:

Originally posted by Devereaux:
Not having yet shot any of those other than short sessions with a friend's .300 BLK in an SBR, I can only speak theoretically, not practically.

Yes, quite true.

quote:

Originally posted by Devereaux:
One of the characteristics of .308 bullets is that they stabilize well....

When bullet type, bullet weight/length, barrel twist rate, and bullet velocity are properly matched -- yes, they can & do fly well.
When these factors aren't properly matched -- not so much.

quote:

Originally posted by Devereaux:
5.56 NATO, on the other hand, is a hot little round that goes fast and is marginally stable at speed.

Incorrect. From shooting tens of thousands of 223 rounds, of various types in multiple platforms, I can state that 223 bullets can be very stable at speed. See my comments above related to 308 bullets.