Troubleshooting feeding and BHO on a new build

[26 Inf]

13.9" Rosco barrel, mid length gas system, standard buffer. When doing the last round BHO test, it fails to lock open. Tried different magazines and replaced the bolt catch. Tried adjustable gas block, it just fails to extract altogether when reducing gas pressure. The only thing I haven't tried is heavier buffer, but I would think I need less mass not more. I am thinking the gas port is too small. Any other ideas?

So I imagine yours is the K9 Greenline Tactical in 5.56. FWIW I have 13.7 Purebred .223 Wylde - it runs like butter on an A5H3.

I recently spent several days at the range dialing in a 16 Dissipator with a rifle length gas system and a rifle length receiver extension.. Getting it to function and pass lock back was easy, getting it to cycle the way I wanted was harder, expecially since I had my choice of rifle, a5 with spacer and carbine with spacer.

What proved invaluable was that ability to change weights around in buffers. I buy tungsten weights from purtungsten.com and all the other components (steel weight, aluminu, weights and rubber spacers as well as buffer bodies from https://kakindustry.com/ar-15-parts/buffer-tubes?page=2. I use a cheapo HF scale - https://www.harborfreight.com/digita..._psugg_q=scale
to check weights.

I'd suggest anyone puts together AR's do the same.

Note: if you are building rifle buffers I would not recommend the KAK rifle buffer body as the base has the aluminum spacer as an integral part of the body itself so you won't really be able to build hevy rifle buffers.

You also need to consider that some times it takes some shooting to seal the gas system - although I've never had that problem using Giessele gas blocks.

You mentioned changing bolt catches. No need to even think about that unless the bolt doesn't lock to the rear when you cycle it with empty magazines inserted and seated.

You also don't mention checking your bolt - look for leakage around the gas key - between the bolt carrier body and the gas key. Check your gas rings:

Per the TM 9-1005-319-23&P.

4. Check bolt assembly (5) for proper fit with bolt cam pin removed. Turn key and bolt carrier assembly (6) and suspend so the bolt assemblyis pointed down.

NOTE: The bolt assembly must not drop out. If weight of bolt assembly allows it to drop out of key and bolt carrier assembly, replace bolt rings (p 3-21).

It's also nice to be able to swap in a known good BCG.

Good Luck!