While MkVIIIz is a popular topic...

[Peter Laidler]

Actions stretching? We had this discussion some time (and tome....) ago regarding L1A1's. How does a rifle action stretch? Put a bolt and nut between a slab of steel, tighten the nut up and the bolt will stretch - if you over tighten it! Because it has exceeded the limits of its mechanical elasticity. This action doesn't happen with a rifle as you have to stretch something between two (or several) points. The bullet passes through the bore and the rifle recoils. The bolt is under tremendous compression and the body might measurably twist and warp and then resume its shape. But it isn't subject to tension.

Many things happen to rifle bodies but 'stretching' ain't one of them!