Locking lug lapping & lapping compound recomendations

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by NorthernSniper, Jul 13, 2006.

  1. NorthernSniper

    NorthernSniper Well-Known Member

    Messages:
    150
    Joined:
    Jul 31, 2003
    I have a Sako with a stainless SM action with 3 locking lugs that I would like to lug lap to try and improve accuracy. What procedure do you use and where can I get lapping compound? What about automotive valve lapping compound? Any help appreciated /ubbthreads/images/graemlins/smile.gif
     
  2. Dan Carey

    Dan Carey Well-Known Member

    Messages:
    65
    Joined:
    Dec 25, 2005
    Lapping the lugs on your Sako will only increase the headspace clearence not the accuracy of the rifle.
     

  3. Bart B

    Bart B Well-Known Member

    Messages:
    2,483
    Joined:
    Dec 25, 2005
    Check out this link:

    http://www.brownells.com/aspx/NS/GunTech/NewsletterArchive.aspx?p=0&t=1&i=527

    You'll need something to hold the bolt lugs against the receiver and use 300 grit if the lugs are pretty smooth; 400 if they're rough. Lube and clean out often.

    Your headspace will open up a couple thousandths of an inch but with most bottleneck cartridges that's not going to matter if you full-length size fired cases and don't set their shoulder back. Belted cases are different; the barrel may need to be set back one turn then rechambered and if this is done it's a good idea to square the receiver front with the tenon thread axis so the barrel shoulder contacts evenly all the way around.

    Lapping bolt lugs to full contact should be done along with squaring up the bolt face with the chamber (not bolt) axis. Otherwise, the impact of the fired case head against the bolt won't be even all the way around. The case head has to impact the bolt face such that forces are transferred evenly to all lugs so the barreled action doesn't whip differently with each shot. Lapping the lugs and squaring the bolt face is the only way I know of to do this.
     
  4. gonehuntingagain

    gonehuntingagain Well-Known Member

    Messages:
    417
    Joined:
    Mar 16, 2003
    I used regular JB bore scrub when I lapped my lugs to make sure I didn't overdo it. It worked well and didn't take too much off at a time.