This has probably already been discussed, so my
apologies. Could someone provide a "stroke-by-stroke" description with product names of an
acceptable way for the average Joe to lap his
own barrel. Thanks

577ne---

First you make a lapping cradle. It holds the barrel blank in line and level with a support/guide block for the hardened steel lapping rod that has a wood screw silver soldered to the front to hold the lap. The support acts like a rod guide to keep the rod from touching the sides of the barrel.

The lap is lead poured into the end of the barrel and against a card wad strung onto the screw end of the lapping rod.

Once the lap is cool you force it *almost* all the way out of the barrel, but not quite. Smear on the lapping compound (available from MSC (800) 645-7270), and then pull the lap *almost* all the way back through the barrel. DON'T allow the lap to disengage from the rifling until you're finished with that grade. Usually it takes from 5 to 25 strokes to lap one grade.

Once that grade is done force the lap from the barrel, melt the lap from the rod, completely clean the barrel, repour a new lap and repeat with a finer grade.

Trim the ends of the barrel where the lap changed direction and you're done.

It's easier to screw up a *finished* barrel by beating it with a hammer or "cleaning" it with a rat-tail file. Lapping is for blanks. The muzzle end in cut off and the butt end is taken out by the chamber.

Is that what you wanted?

JBelk: Yes and thank you. How many grades of
compound do you use, and how thick (much) lead
do you pour in? Do you think the benefits
justify the effort?

I'll add a couple of things to what Jack said. I use the cores of worn out cleaning brushes as the core for the lap. I wrap a thin strip of cloth or even some string around the base. Warm the muzzle end of the barrel prior to pouring the lap so the lead does not set up too quickly.
The grit used is dependent to a large extent on what is being done. Normally lapping is used to achieve a desired surface finish in the bore and not to correct any dimensional deficiencies but it may be used for this as well (and was in the old days). If the intent is to simply smooth out a microscopically rough barrel then the use of a 600-800 grit compound is fine.
If, instead, you are wanting to remove a tight spot or in some other way improve the uniformity of the bore, then you might start witheven a 280 grit.
It takes a LOT of lapping to have much affect on dimensions.
It is possible to lap a finish barrel and improve it if it has a problem related to finish or a tight spot. The technique is modified a bit to avoid any belling of the muzzle. A plug with a through hole made to fit in the chamber will align the rod and limit rearward travel of the lap.
In practice, I charge the lap and draw it to the breech then work my way to the muzzle using short back and forth strokes. I then take a half dozen full length strokes. If there is an obvious tight spot I will concentrate on that then go back to the full length strokes. If the lap loosens in the bore I will periodically run a rod down and bump the lap to increase it's diameter.
I have seen some original military barrels that had places that were tight by over .001. It takes a lot of effort to remove this much with a lap.
I have to say that with any decent barrel their are no significant tight spots and seldom any taper. Also the finish, even in the good cut rifled barrels, is so good it is unlikely you can improve it. I know one maker who cut rifles and does not lap because he says, "The barrel is perfect now! Why screw it up with a lap?"
He also makes gain twist barrels which cannot be lapped.
In the days of the muzzle loader it was common practice to lap the barrel so as to leave a choke of about .001 at the muzzle end. That is not done now. The one barrel maker I knew who claimed to choke his barrels in modern times made a product that was so inconsistent that the choke could have been at either end or in the middle for that matter.
So, in the end, lapping can improve a bad barrel if it is done correctly. It can also hurt a good barrel if done wrong. Also if you think you are going to lap a .318 dia mauser barrel out to 323 you'd better pack a big lunch! Regards, Bill.

A lap should be about an inch an a half long. Normally three grades are needed to take the bore from machined finish to semi-mirror.

There is absolutely and positively NO reason to lap ANY barrel unless it's been terribly abused already or has an obvious problem. (Pitting, damage from shooting with dirt in it, dirt dauber nest, rat pee, etc)

If you buy a decent barrel it's already been lapped. To relap it is the absolute last resort to try to save it.

Good post, Bill. We were writing at the same time.

[ 10-31-2002, 20:49: Message edited by: JBelk ]

Thanks very much guys-my questions have been answered

I would add to the wonderful answers of the others, that fire-lapping is probably a much easier alternative if you are wanting to lap a barrel that is already chambered.