I ran the same ammo in a 10.5 inch 300 BO build and had no problems
Steel seems to be the one thing you changed so only brass moving forward. Steel is cheaper and more available but if it doesnât work properly it gots to go.
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The gun seems undergassed. Measure the gas port. It should be about 0.101 for reliable function with subs and supers, and crappy steel ammo. An OSS can will not improve the function since there is no associated increase in backpressure. All this assumed a standard carbine buffer spring, a standard 3 oz. buffer, and a pistol length gas system. Drilling out a gas port is easy, but not for the faint of heart. Have a gun smith do it if you have any doubts about your abilities. Your problem is not uncommon, and I had experienced, (and solved), the same one. Many manufacturers assume if you shoot subs, youâll use a can, and standard cans provide the extra gas pressure needed. OSS cans are the exception.
Would something like this help?
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Try another brand of steel cased ammo. If other ammo cycles fine you may just have gotten some weak ammo.
You could put a silencer on it to create more back pressure. Or run a lighter buffer⌠I prefer the silencer. ; )
My 10.5 300blk (odin works barrel, stag arms upper and bcg, standard buffer) ran fmj subs and supers just fine, but it had trouble cycling subsonic hollow points (all brass cased ammo). Changing to magpul gen 3 300blk specific pmags solved my cycling issues. Changing mags may not solve your problem, but it might be worth a shot before you do something big like drill out your gas port.
Iâve got a 300 Blk PSA upper and lower, 8.5â barrel with a .700â barrel extension. Mine shoots Barnaul steel case just fine. So far it shoots anything supersonic.
Subsonic it short strokes, not advancing the next round after ejecting the spent casing. I have a short term and long term fix in the works though.
@rockymountainjeep the reason it short strokes is that you donât have a can on it. 300blk subs were meant to be run suppressed.
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I really like that 4 piece flash hider - there are some youtube videos demoâing and describing it. This video mentions that it boosts back-pressure, and is very good at hiding flash on both long- and short-barreled rifles. I donât think any AâTâF stuff is required. PSA sells a couple variants, but not sure why they say âfauxâ. Could be an inner cup that the Bulgarian version uses for back-pressure. Also, the ak-builder.com version has several threading selections including 5/8-24 (typical 30 cal. AR), and 1/2-28.