Gas Block Lapping

[MKChastain]

Howdy all,

I am a little confused about this gas block lapping that several have written about.

If you still have a gap between the two housings after lapping, then why lap at all? I can see how it is important to ensure equal gaps, alignment issues and such, but lapping seems immaterial if a gap still exists.

Please educate me!

Thanks

Mike

[Mike McDonald]

The logic as I understand it is to provide parallel surfaces so you can get a true reading when you measure the gap. Right?

[ovpham]

:) I believe the idea is to have an even gap so the internally polished surfaces of the two pieces are actually touching the barrel surface evenly to seal and to expand evenly under the influence of the heat generated by the fired cartridges.

If the two pieces of the gas block touch one another, there will be a leak of hot gases that varies widely when the metal expand and push each other at the point of contact (metals expand when heated). The result is random or unpredictable shot placement or shot walking in a preferred direction.