Feed ramp/ lugs question

[LRRPF52]

Another issue is that many bolts aren’t machined with the correct dimensions for the barrel extension teeth clearance, so you can run into a situation where lugs are grinding against the teeth as the bolt telescopes in and out through the extension once it’s unlocked or returning to battery. We’ve seen a lot of this on 5.56 and .308 rifles where a DIY approach, or even manufactured rifle, have interference between the lugs and teeth.

Some of that is caused by barrel extensions not being timed correctly relative to the upper receiver. This is controlled by the index pin placement and perpendicular installation to the tangent of the extension, as well as how the installer torqued the barrel nut into place.

I avoid this problem by checking the fit and articulation in-advance, then setting the barrel extension timing by bedding it well before I ever torque the barrel nut on, so there is no way for the extension to wiggle out of place.

Basically, the whole way I approach an AR-15 build today resembles nothing how I did it back in the 1990s-2000s. It doesn’t even feel like working on the same gun.