Ridges inside BCG? Purpose?

AR/M4 AR General Discussion
1

I have noticed that my BCG’s seem to have very tiny “ridges” inside the gas-chamber. This can both be felt in the gas-ring region, and heard (as a szzz-szzz-szzz when moving the bolt in and out along its travel, or as a rough-ness when sliding the fingernail inside and out along the chamber wall near the mouth), when sliding the bolt in and out. Much moreso on new BCG’s than used one’s, though.

Do the ridges serve a purpose, like the cross-hash inside a cylinder wall on an engine?

2

No purpose…

Just a difference in feeds and speeds during the manufacturing process. someone is pushing tooling to increase cycle times, and that is the nature of manufacturing. Some people do an I.D. Grind to finish the inside, and some people turn on size.