Home Forums Hunting & Shooting Gunsmithing Blueprinting V/S Square & Lap REM 700 Action

Ditto...... A very LONG mandrel -

So you never find the need for lapping bolt lugs? Just curious here..


FWIW, I only lap lugs when I see it's necessary - otherwise I do not..

Lee, on a Remington 7-700 family, I think it is a waste of time if the bolt body is not bushed to fit the receiver bore.

The need/requirement to LAP lugs signifies the set-up/operation needed to be verified.

I've seen lugs that are galled. I've seen lugs that only contact on one lug and not the other.. As long as contact is a relatively even percentage of contact and are not galled, they're left alone..

I've had a couple of bolts with lugs off enough that they had to be recut in order to get them right..(not just Rem.) We're talkin' .001-.005 here usually.. I remember reading of a rifle-builder that found one bolt off by .014!!

It does happen..

Those systems save time for the gunsmith and therefore are a money maker. The only problem the "very quality product" isn't actually true when they get finished. A tap will follow the hole (you know the hole that's not on center and radially out as well) no matter how many bushings are guiding it. There's only one way to get it right and it's not with a tap.

I may be off base, but to me it reads like sometimes Lee and Dan aren't addressing quite the same thing. My impression:

Dan: After fully machining the bolt and action, if the set up was correct then the bolt lugs should evenly contact the lug seats in the receiver. No lapping required.

Lee: On a basic rebarrel job where squaring the face of the receiver is to be the extent of the machining as long as nothing else is way out, a bit of lapping can improve the mating of bolt lugs and lug seats in the receiver.

When I first started truing Remington actions (and others), around 1978, I mounted the receiver on a close fitting mandrel and installed a sacrificial sleeve which would run in the steady. The sleeve was glued on with five minute epoxy and trued with the mandrel held between centers. While this seemed to work fine, it was a bit of a hassle so I made up spiders which would serve the same purpose. These were mounted on the receiver ring then trued just as the glueed on sleeves were. The next move was to build a jig of heavy-walled steel tubing which would allow the receiver to be set up so the jig was co-axial tothe receiver bore. The jig was then set up in the four jaw and steady and the truing cuts were made on the receiver. I still use this method, with some variations according to whim.
At the time I was using the sleeve on the receiver ring, I also messed with a cast iron lap with a floating pilot which I would use to finish the locking lug seats but I soon gave up on that.
I started out bushing bolts but soon switched to retro-fitting bumps which I accomplished by using inserts dove-tailed into the bolt body and trued to the centerline.
Prior to all of this, I simply faced the receiver while it was held on a mandrel, then lapped the bolt lugs in. I used shim stock wrapped around the rear of the bolt to tighten it up in the receiver while lapping. I did not bush the bolt early on. I found that tightening of the rear of the bolt in the receiver did reduce the vertical in my groups (by about .050") and think that any scheme to tighten up this fit is worthwhile in a match rifle. I recall seeing one action where the owner/ 'smith had installed four setscrews in the receiver to center the bolt. This approaches the problem from a different direction but I have no reason to think it wouldn't work except that it seemed a little finicky to set up, to me. After forty years and an uncounted number of Remington, Winchester, Ruger, Sako, Howa, Enfield, and Shilen actions being trued, I still have never been able to quantify what improvement there may be, if any. The exception is with the tightening of the bolt which, in that one 40X-based rifle, was good for about .050" inch of vertcal at 100 yd. GD

Pretty much....

I’ve read that argument also. Have you ever used one and measured the results?

greydog, very good bit of knowledge passed along there and in a professional way. Thank you. I by no means have your level of experience but what you have relayed is very much in line with what I have seen.

People expect an action blueprint job on their factory rig with a new barrel, so the gunsmith provides it. How it’s done can vary greatly and the results are often times not easy to quantify. And somewhere in there the gunsmith has to pay the bills, and that’s not easily done spending all day on one $125 action job. These things are learned with experience, much in the same way that accuracy guarantees are not extremely valuable.

I have checked the results of the guided tap method. It's not difficult to check the quality of the work by chucking up a cutoff stub and cutting a shoulder and threading it. Put a good mandrel in the bolt way of the receiver and snug it up on the stub that is still in the lathe. Put a indicator on the mandrel and check the runout. The piloted tap method move the centerline closer to correct and take out some of the radial problems as well, but it will not true the action. The only way to get it right is single point trueing in a lathe with good setup practices and good work holding capabilities. The take home message to those considering action trueing services is BUYER BEWARE. Know what it takes to get the job done right.

Nice. Thanks for sharing your technique.