Gunsmithing Lug Bedding Question: what is the purpose of the relief cuts?

[Gene Poole]

I've bedded the recoil lug area on a few stocks with aluminum v-blocks (B&C and HS Precision) and they both have cutouts on either side of the lug contact area. I've always assumed these were there for a reason and fill these with putty when bedding so they remain open when done. I was questioned about why I don't just fill them in and had no good answer except that the manufacturer seemed to think it was necessary.

What are they for and should they be left open or filled in when bedding the lug area?

 

[alf]

I grind out part of the bedding block to make room for the bedding, so as not to rely on the block to be square to my lug. I tape off the front, sides, and bottom of the lug with two layers of tape for clearance, and fill 'er up with bedding.

 

[LRI]

A relief cut or "dog boned corner" as its sometimes called is a byproduct of machining this feature in a vertical mill. An endmill, regardless of size is going to create a corner radius as it machines the pocket feature that the lug registers into. Unless the lug has a mirror image of that radius, it won't seat against the stock, it'll be suspended ahead of it due to the corners "biting". There's an almost infinite number of recoil lugs available for M700's these days. The shapes and sizes vary considerably. Stock manufacturers are attempting to address this challenge by hitting the widest margin possible.

The dog bone feature allows the lug to seat in its proper location. Filling it likely has no effect on performance and done incorrectly, it can make a real mess of things.

C.

 

[Boogyman]

I bed it the exact same way Alf does so 2nd on what he says!