How To Hand Lap A Barrel

September 23, 2010

(left) This French Berthier

Model 1916/1927 probably

saw utilize during Globe War I and has a less than perfect bore. Its bore can be improved by lapping using a pb slug.

(center) Coffield uses a hot air gun to heat the barrel prior to casting the lap in the bore.

(right) Make certain y'all have a very sturdy rod for the lap. Coffield uses an erstwhile surplus M14 steel cleaning rod.

If someone suggested you rub the within of your burglarize barrel with sand, would you do it? That's a pretty stupid question, right? Of grade you lot wouldn't.

From day one, nosotros're taught to treat the bore with TLC. Nosotros're admonished by every gun expert, cocky-proclaimed and otherwise, to be extra careful and never allow the slightest amount of wear or smallest bit of abrasive to make fifty-fifty the tiniest scratch inside the barrel.The burglarize bore is one of those mysterious and sacred areas we tin can only approach with intendance and by following the specific instructions of experts. Later all, if we do anything incorrect, we'll ruin the butt, or so we're told. Just like and then much pop wisdom, that's not always true.

Over the years, I've developed an interest in older military commodities-action rifles. One of the things I've discovered is if I can afford the rifle, it's probably not in the best shape. In fact, information technology's pretty condom to say it'll exist darn rough! That's okay with me; I'd much rather take a rifle that saw use than a mint-status example that was never issued.

---

The problem with these old rifles is compounded by the fact that most military ammo used up through the end of Globe War II had corrosive primers. If yous're standing in mud with somebody shooting at you, you seldom have the time or inclination to go through all the machinations necessary to thoroughly clean your burglarize after firing corrosive ammo. Consequently, many--if non about--of these old warhorses accept pretty rough bores with pitting ranging from calorie-free to "oh my gosh."

Recommended

(left) A uncomplicated Lee melting pot is ideal for preparing the atomic number 82.
(center) A minor, coarse, flat file is used to cut grooves around the lap (top), and the abrasive paste is practical sparingly to the lap
(correct) Clover lapping compound is a grease-based silicone carbide annoying available at many car parts stores.

If I merely wanted to hang these old rifles on the wall, the bore status wouldn't matter all that much. But for me, function of the romance of these rifles is taking them to the range and firing them. Information technology's one thing to read about 'em, but I want to know what it feels like, how it sounds, and even its aroma after firing.

The problems with a rough bore are that it hurts accuracy and leads to excessive fouling. The pits actually rip metal from the bullet as it passes down the bore. If nil else, this roughness makes cleaning a real chore.

I way to deal with a bad barrel is to smooth the bore and remove, or at to the lowest degree lessen, the effects of the pitting. That'southward were the sand comes in.

The merely way to smooth the bore is to go over it with an annoying such as silicone carbide, which is basically similar super-fine sand. There are two ways of getting the annoying into the diameter. The quickest is to coat a bullet with abrasive and fire it through the bore. This is called fire lapping and has become quite pop in the last few years. The other method, which I prefer, is a more than traditional lapping technique using a pb slug, abrasive, and a sturdy rod. Now keep in listen that I'm talking about rifles with barrels simply one step away from existence used as tomato stakes. I'1000 not talking about super-nice commercial barrels or wringing sub-minute-of-angle accuracy from them. If you've got a barrel like that, go run across a good gunsmith. I'm dealing with ratty onetime barrels, and any improvement I make is a cyberspace gain.

(left) The molten lead is carefully poured into the muzzle end of the barrel.
(center) Note the atomic number 82 "button" that has formed as the atomic number 82 spreads out into the crown of the cage. The flange of the "push button" must be removed before the lap tin be pulled into the diameter.
(right) A minor, coarse, flat file is used to cut grooves around the lap (top), and the abrasive paste is practical sparingly to the lap (lesser).

Traditional pb lapping of a barrel begins past disassembling the burglarize and thoroughly cleaning the diameter. Spend as much time as necessary to remove whatsoever carbon or bullet-jacket fouling. After an extensive cleaning, you lot may exist surprised to discover the bore actually looks worse and even rougher! In cleaning, y'all may have emptied the pits of built-up fouling, and the bore appears to be worse. That has happened to me on a number of occasions.

With the diameter cleaned, accept a sturdy cleaning rod with a jag or metal patch loop and insert it from the breech end until the jag or loop and a half-inch or so of the rod projects from the muzzle. Accept a bit of regular cotton fiber twine and wrap information technology effectually the rod only alee of the cage. Utilise enough twine to grade a good seal around the rod. This volition prevent the liquid lead we use to grade the lap from flowing by the twine seal and into the butt.

Use a hot air gun or propane torch to oestrus the barrel from the muzzle back near 3 or four inches or so. The barrel doesn't take to be super hot, just very warm to the affect. A heated barrel will minimize voids or imperfections in the pb casting. It's also a good idea to oestrus the jag or loop.

Cotton twine is wrapped around the rod to seal the diameter nether the pb lap.

When you have information technology properly heated, pull the rod back into the barrel until the meridian of the loop is about i inch below the cage. Cascade in melted lead until the lead is fifty-fifty with the muzzle. Needless to say, exist darn conscientious and wear gloves and protective wearable. Hot, molten lead can cause severe burns. That's too another good reason to have the barreled action out of the stock and supported in a padded vise.

By the way, I use almost pure atomic number 82 considering it's softer than atomic number 82 with a high tin or antimony content. The p

ure-lead lap moves through the bore much easier than a hard pb-blend lap.

Allow a few minutes for the pb lap to cool and solidify. Next, push the rod from the breech and so the lap extends forrard out of the cage about 3 inches. I use a vi-inch coarse apartment file to remove whatever lead extending out further than the diameter of the diameter. Mostly in that location'south a "button" of pb that extends into the crown. If you lot don't file information technology abroad, you'll never be able to pull the lap through the butt.

Use a small file to cut some grooves around the lap. This can be one long spiral groove or several dissever circular grooves; it actually doesn't matter. The important thing is that you have these grooves to help carry some of the lapping abrasive.

Coffield prefers nigh pure lead for barrel lapping.

While you could use almost any annoying, with these erstwhile barrels I accept found that Clover silicone carbide grease-based annoying--by and large available in automotive parts stores--works just fine. I have a shop sampler kit with 2-ounce tins in grits from 120 up to 800. I seldom need to use finer than the 240 grit.

I use the grit by merely putting a bit on my finger and rubbing it over the lap. It doesn't take much. In fact, if you lot utilise too much, it'll make pulling the lap through the bore well-nigh impossible.

With the lap loaded with abrasive, the cleaning rod is pulled back through the bore. By the manner, I utilize an old cleaning rod designed for utilise with the M14 burglarize. Be very careful that you lot don't pull the rod then far that the lap disengages from the rifling. If you accidentally pull the lap out of the barrel, just melt the lap off the rod and starting time over. A slice of record wrapped around the rod about 4 inches below the lap is a skilful, simple means of keeping track of the location of the lap as it nears the chamber.

Pulling the lap through the barrel can be very tough initially, specially if the bore is rough. As you work the lap back and along in the barrel, it will begin to move more easily. After about a dozen strokes or so, y'all'll feel a noticeable departure. This is due to wear on the lap and the abrasive smoothing the diameter.

As the lap wears, you lot'll want to melt off the sometime one and recast a new, tight lap. I use my hot air gun to do this, but you can also employ a propane torch. I more often than not supercede the lap three or four times while using the same grit of abrasive. Once I accept completed a series of three or 4 laps with the initial 120-dust annoying, I clean the barrel and check my work.

I more often than not notice a significant difference in how easily a cleaning patch will move through the bore. There is as well a visual deviation in the effulgence of the diameter. It just looks ameliorate!

Depending upon the condition of the bore, I echo this bike of steps with 180- then 240-grit abrasive. Each fourth dimension, the bore should expect and feel smoother. Just how far you should go with higher dust abrasives or how long you should lap the barrel is entirely subjective. Do information technology until you lot're satisfied. If you later determine you want the bore smoother, just pull out the lapping supplies and become for it.

Lapping former military rifles will not make a rusty tube into a prize-winning match barrel, but it can help to make the rifle more enjoyable to shoot. Information technology's just amazing what y'all tin do with a fiddling bit of sand.

Until next time, good luck and good gunsmithing.

Source: https://www.shootingtimes.com/editorial/gunsmithing_st_lappingbarrel_200805/100288

Share this post