AR Tuning question

[brutus1776]

I have a BCM 14.5 rifle with stock bcm buffer system. I shot out the stock barrel, rebarreled with Gieselle 14.5 chf. Superlative adjustable gas. Stock bolt. I ran it in a class for 1500 rounds. No problems. I put on an sjc titan brake. The rifle runs but will not lock back on the last round. Even with full gas. When you hold bolt stop down on last round, it locks back on the carrier not bolt face. I put in a jp scs with stock spring out of another rifle and it works with full gas and locks back, but move that gas 1 click and doesn’t lock back.

What do I need to change on this? Lighter spring? Carrier? Buffer weight? Thanks!

 

[slodsm]

To me that sounds like buffer weight. A lighter spring will do the same, but it’s going to slingshot the existing buffer into the back of the extension hard as cause a screwy recoil impulse.

That’s just my experience with them.

 

[TonyAngel]

I have a BCM 14.5 rifle with stock bcm buffer system. I shot out the stock barrel, rebarreled with Gieselle 14.5 chf. Superlative adjustable gas. Stock bolt. I ran it in a class for 1500 rounds. No problems. I put on an sjc titan brake. The rifle runs but will not lock back on the last round. Even with full gas. When you hold bolt stop down on last round, it locks back on the carrier not bolt face. I put in a jp scs with stock spring out of another rifle and it works with full gas and locks back, but move that gas 1 click and doesn’t lock back.

What do I need to change on this? Lighter spring? Carrier? Buffer weight? Thanks!

The smart ass response that popped into my head was to say get rid of the brake.

There are a couple of things you can do. First, if you're running the setup 1500 rounds at a time, I definitely wouldn't go lighter on the spring. That will probably cause you to have failures to go into battery when it gets dirty. This is, of course, assuming that you're using what would be considered the standard rate spring. If you're using a heavier spring, then drop down to whatever would be considered stock.

You could get rid of the adjustable gas block. All AGBs leak at least a bit. You could also reduce the buffer weight.

I'd get rid of the adjustable gas block and tune with buffer. weight.