Steve L

Yup, mine has a bit more play than I like but shoots well enough!

I have an 8" 300 AAC barrel with a gas port of 0.097". Unfortunately, I received the barrel cheap and the previous owner did not know who the manufacturer is. I figured if it sucked then I'll buy a new one. It shoots very well so far!

It is not too difficult to get the 150 gr FMJBT to fire subsonic. The challenge is generating enough gas pressure to completely cycle the action. Last monday I shot a few of my subs using Trail Boss to test for basic functionality. The load is well known to be subsonic and it is also well known to not cycle an AR. I did not chrono it so I cannot confirm it was truly subsonic but the recoil was greatly reduced and it sounded much quieter than then my supers (my perception/no suppressors with ear pro). My calculations on felt recoil show my supers (1620 fps) at 5.6 ft lbs and my subs (if under 1100 fps) should have a felt recoil of 2.0 ft lbs. Now the fun part is getting the subs to cycle. Likely looking at some new powders before I start drilling out gas ports and playing with buffers/spring rates. I have a few ideas! [Insert Dr Evil laugh here] As you can see, like most of us here, I know getting 150 subs is a bit of a challenge which is what motivates me! The heavy subs have been proven to work well and is my fallback position.

Bummer. My 300 BO barrel has a port size of 0.097". I don't want to start drilling unless I really have to. It perfectly feeds the supers but I'm trying to get 150 gr FMJ subs to work. It doesn't like the 150 FMJ-BT. I can only barely move the bolt. I know the 'why' question will pop up. The 150 FMJ-BT allows me to shoot more since they are more affordable and it seems to be a very challenging load.

Thank-you everyone!

Thank-you sir!

Does this info exist elsewhere? This link is dead.

I purchased an adjustable gas based on hearing that 308 ARs were known to be over-gassed. This too has been my experience with my 308. I was having my rifle attempting to extract the casing before the casing had time to cool/shrink. This was a timing issue that the adjustable gas block cured. Given my experience is limited and I have a lot to learn yet. Dialing back the pressure has made the difference plus my brass no longer has ejector marks. FWIW: Hornady markets their Superperformance ammunition as a solution for over-gassed ARs. Link - https://www.hornady.com/support/superformance-in-gas-operated-firearms

Hello group! Yes I am new here and I have noticed a similar occurrence with my M5 Aero (up/low/buffer/spring/tube,ptk). I have an Anderson 18" barrel and adjustable gas block (I have to stretch my allowance across way too many hobbies). With my GB full open the rifle was bucking quite hard. Marking up the buffer, flattening primers, FTE, popping out primers and leaving ejector marks. I even had the extractor pull the rim off a stubbornly stuck cartridge that wouldn't eject. Unfortunately, I tried too early to bring in my reloads and confused the issue with the signature of overloaded cartridges. After tweaking the GB just to the point where it would fully cycle and lock back on an empty mag using factory loads the rifle is now much tamer. I hope my experience helps. BTW, I'm not an expert just a very curious enthusiast who isn't afraid to learn new tricks! :-) Steve

Hello group, I just wanted to introduce myself to the group. I have been shooting my whole life and I enjoy target shooting. I have also been reloading pistol (9mm, 380 and 45) for about 15 years and rifle (223, 308 & 300 BLK) for about 2 years. I have been introduced to the AR platform a few years ago by a friend who has made me divert my precious allowance into building ARs. I paid him back by getting him hooked on reloading! I own a number of non-ARs rifles and quite a few handguns, I have built 3 ARs. My first was my learning rifle consisting of a Bushmaster Patrolman complete upper in 5.56 and I assembled the lower. My second was an Aero Precision M5 308 (upper/lower) which I built completely. My third was an Aero Precision 300 BLK pistol soon to be SBR. My attention is now focused on why my Aero M5 is flattening primers (even with factory ammo and adjustable gas block) and developing a good subsonic load for 300 BLK using a 150 gr bullet. That should be enough to get me started. I left a lot of specifics out but feel free to ask if you have any questions! Steve