AR Thread

[steven]

I was under the impression that the HPT process was basically subjecting the bolt to a proof test, which also has the effect of potentially shortening the overall life of the bolt by quite a margin. I read that the US army found that bolts (even HPT/MPI tested) will begin to crack at 5,000 rounds, and will generally break at 10,000 rounds.

If bolts tend to let go at the same time, I'm not sure if the benefits of HPT stack up, but interested in others views.

All colt bolts as far as I know are tested and marked MPI. Many others do not or batch test only.

Personally when I have a new boiler (or any pressure vessel) a 1.5x or 2x overload test is the normal for insurance / QA purposes and gives some assurance that there is no serious but hidden unique defect. So no it doesnt or should not shorten the life for a component as a one off when new.

Army, well apparently they replace the bolt at 7500rounds or so as they do a lot of auto fire which really stresses the bolt. Again from what I can read 20,000 rounds or 2 or 3 barrels in a "retail" environment ie you and I is quite typical. Bolts are however really cheap and getting a matched bolt and barrel seems to be the best option for accuracy and long life.