Lapping bolt lugs??

[TLARbb]

Did not know where to ask this question, but seeing as it is a Remington action, I thought this would be as good a place as any to ask?

Is lapping in bolt lugs something that I should try at home?

If so, what's the best procedure and materials to use?

What are the pitfalls and gotchas of doing this?

Regards,
EJ

[springer222]

If you have never lapped bolt/receiver lugs, I would suggest that you seek advice from either someone with experience in this area or find some material that has detailed explanations. Although I am far from an expert, I have done a few. Information acquired with from folks with experience have led me to believe that most new people have a tendency to "overlap" or go to far while lapping lugs (completely opening the bolt during each lapping cycle). I think, IIRC, most look to ~70-80% contact (someone correct me if I'm wrong here) while never completely opening the bolt to keep from "rounding" as the bolt begins to close.

As for tools, there is a jig that can either be purchased or made that holds "pressure" against the bolt, keeping the bolt and receiver lugs engaged. It's threaded to fit the receive, with a spring that holds a pin that "pushes" against the bolt. Also, there must be some type of lapping compound to "cut" the surfaces. And finally, once the contact surfaces are lapped, it is extremely critical to remove all lapping compound or the grit will continue cutting any and all surfaces in comes in contact with. A parts washer is one of the best things I used for this step.

This is not something that is overly complex, but again, I would suggest you seek advice from someone with experience or find very detailed material. And go slow, checking often.

[charles p]

Gunsmith loaned me the jig and gave me compound and instructions.  Had to keep oil on the cocking cam (??) to prevent unwanted wear.  Took about a six pack and a Monday night football game to get it done.  Smooth as glass now.  Was an old Rem 700.

[gunnut69]

The best jig uses a solid pin pushing against the bolt face to apply the pressure to the lugs. This will help aviod the rounding over of the initiating surfaces of the locking lugs.. This is done with the barrel removed, to adjust the locking lugs contact with a barrel installed would lengthen the headspace and perhaps create a dangerous condition.. As to contact amounts I would consider anything over 60-65 percent as sufficient for a hunting rifle and 75-80 is likely enough for anything,. when lapping do not fully disengage the lugs and their abutments. Just move the lugs on the flat forward surfaces of the abutments to abrade both equally. The sping loaded jig allows the lugs to move forward and backward as they are turned. This can lap in slopes in the two engagement surfaces.. A solid metal slug pushing on the bolt applies the most pressure at the top of the sloping surfaces. It thus tends to level the surfaces bing lapped.. This is a simple sounding process with some far reaching and potentially dangerous effects.

[Nobade]

A couple of other points...if you lap lugs for full contact with the barrel in place, you now have made your bolt face crooked. The sear bar holds the bolt up, in contact with the top of its raceway when cocked. The lower lug is touching, and not the top one. If you wear away the lower one so the top touches, the lower is now thinner and when the rifle is fired, the bolt will no longer be straight at the moment the case head slams into it. Think about what this does to your cases, not to mention the bending moment it introduces into the reciever. One other thing is, if you haven't removed the barrel how are you going to get all the lapping compound out? Unless you use an ultrasonic cleaner, there is always going to be a little in there to keep wearing things. 

[gunnut69]

Of course the sear will no longer be supporting the bolt when it is released to fire the rifle?? Also the pressure on the bolt face(which we assume is square to the centerline of the action) will immediately make the question mute as it will slam the lugs into contact with their respective abutments. Squaring a lock recess and the lug faces to the center line of the action is one of the things we want in a well built action. Ensuring the barrel is square to the same centerline is another. Lapping lugs and getting the remaining abrasive out is action suicide..