Shop-made Lapping Tool

As many of you know, lapping the lugs of the bolt and the locking recesses of the receiver in most rifles is an important part of the accurizing process. However, until recently, the only way I knew to do this was to first remove the barrel, apply lapping compound to the mating surfaces of the bolt and receiver, and then screw into the receiver a thread-specific tool for that particular brand of rifle.

With that all done, the gunsmith uses this set up to put rearward pressure on the bolt and then work the bolt in and out, lapping the aforementioned surfaces. There are several possible negatives in this method: The first is the need to remove the barrel. Many Ruger barrels are known to be extremely difficult to remove, even if you have the complex and heavy-duty barrel vise these jobs require. Ditto many (most?) surplus military rifles; did someone say Mosin-Nagant?

Then, there is the little item of the thead-and-brand-specific tool I mentioned. They usually consist of an adapter or insert which screws into the forward end of the receiver. Inside this component is a powerful spring and plunger which together exerts the necessary rearward pressure on the bolt. Fine, you say, but rifles have different threads. Before long, you will want a Remington 700 adapter, one for a Ruger, at least one for Winchester, Savage, Weatherby, maybe Sako, etc.

This does not count the possibility of military surplus rifles such as the Mosin-Nagant or even an AK-47. If you can find just these adapters, you will have something like $450 in tooling. My buddy gunsmith, Mike Dietrich, says he has over $1,000 in these kinds of tools and adapters, not counting the barrel vise that looks strong enough to remove a tank of a barrel… provided you can rotate the receiver!

Even if you have one of these vises (I don’t) and the needed tooling, you still face the arduous task of clamping the barrel and separating the barrel and receiver!

However, on a random Wednesday night, Mike’s fertile mind just changed everything when he came up with one of those ideas that when you first hear it, you slap yourself on the side of the head and say, "Why didn’t I think of that?" In fact, I wanted to entitle this article, "A Brilliant New Look…" but was afraid everyone would see it and say "Briggs is calling himself brilliant?" Here’s what Mike did.

First, he took an empty brass case in the same cartridge the rifle is chambered for and cut a 3/8" section out of the middle using a cutoff wheel in his Dremel tool. Then, he filed and deburred the new cuts of the top and bottom pieces. Next, he cut some off the neck of the brass, deburred it, placed a little tape over the shoulder end, and closed that end with a little epoxy. However, he did leave about 5/16" of it open at the rear.

When the epoxy at the front end of the deburred cartridge front had hardened, he removed the tape and selected a reasonably-strong compression spring from his "miscellaneous spring drawer"—we all have one of those, don’t we? After some experimenting with cutting coils off, he epoxied the spring into both open ends of this new "cartridge". Waiting a day for full curing of the epoxy, Mike was ready to lap the lugs.

To use this new tool, begin by applying a little Dykem layout fluid to gauge progress. Add a dab of 600-800 grit lapping compound to the primary recoil lugs of the action—not the bolt, because the compound has a tendency to just wipe off the bolt lugs and not do its job.

Then, as the bolt is closed to chamber this springloaded cartridge, instead of allowing the complete closing of the bolt, the spring pushes back on the bolt and against the lugs, allowing you to work the bolt handle and lap the For the cost of a spent case, a scrap box spring, a dab of epoxy, and a little labor, you can lap a rifle’s lugs without having to remove the barrel and without needing to buy an expensive rifle-specific adapter! And this new adapter is reusable, job after job. This has to be a win-win.

In addition, these are cartridgespecific lapping tools but are not manufacturer-specific. In other words, one made for a 308 Winchester should work for Ruger, Remington, or Winchester rifles chambered in 308 Winchester, again saving you some serious money. I asked Mike if he would be interested in making multi-caliber kits for sale to the trade but he’s just more interested in helping other gunsmiths, like with this article. However, he would consider it if there is enough interest.

Mike can be contacted at gunsmith_25@ verizon.net. AG lugs! The example shown here was for a 308 Winchester, but virtually any cartridge adapter can be made. American Gunsmith Reader Services 1.