Excuse To Lap Bolt

[ttwn0324]

Haven't seen a better one. Just that wee little bit on the top left lug is all there is for contact.

1151

[timshufflin]

What if it was lapped by somebody else? I am just not a subscriber to the lapping theory.

[ttwn0324]

May have been but not to the receiver it's going in. And the two other bolts I have came out to about the same pattern. So, before I did head spacing I wanted to get better contact on the lugs, instead of hoping for the best as the two mate up under operation.

[timshufflin]

If it was lapped before, you can count on about .005" have been removed from the lug, maybe more or less. If you lap it again, how much will you remove? Maybe .005"? The hardness to start is about .012" thick, there might not be much hardness left... Of course, this is all maybe's and theory.

[ttwn0324]

Yeah, I get your point. Guess just play the odds Beretta didn't

[Old Guard]

Hi, where can I get a little more info on this lapping theory..I was reading about needing good full contact on both sides of the bolt for accruacy??From a M1 garand and M-14...Is there some details somewhere close, I love to read items of interest..Plus is it like just adding Blue or Dykum to the lugs and operating to check for best contact..yes, I saw the part about removing too much and opening up the headspace.

[Old Guard]

If it was lapped before, you can count on about .005" have been removed from the lug, maybe more or less. If you lap it again, how much will you remove? Maybe .005"? The hardness to start is about .012" thick, there might not be much hardness left... Of course, this is all maybe's and theory.

Tim, you are removing the bolt and looking at the lugs contact???The surface is the only hardened part of the lug on it??

[timshufflin]

Tim, you are removing the bolt and looking at the lugs contact???The surface is the only hardened part of the lug on it??

The entire bolt is hardened to about .012" thick or so.

[ttwn0324]

Hi, where can I get a little more info on this lapping theory..I was reading about needing good full contact on both sides of the bolt for accruacy??From a M1 garand and M-14...Is there some details somewhere close, I love to read items of interest..Plus is it like just adding Blue or Dykum to the lugs and operating to check for best contact..yes, I saw the part about removing too much and opening up the headspace.

Best place you'll find theory on it is in articles about building precession bolt actions. I believe it was with Mauser actions were it became mainstream. I wouldn't say lapping the bolt on a M1, M14 or M16 does much for accuracy, more of anal thing I guess. The bolt above was NOS and took less then 40 turns with 600 grit compound to get about 75% contact, at which point I stopped.

[Old Guard]

Awesome, just what I needed to know..your 40 cycles was a very good description..Thanks. OG