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How does one go about measuring a barrel's diameter without damaging it? It seems that the only way to measure a semi-auto's barrel dia. with a caliper is to measure at the muzzle end, and all of the accurate calipers I have seen are made of metal, surely putting the crown of the barrel in such jeopardy by using a metal caliper is not the best way.

I would appreciate it if you guys shared an accurate method of measuring a barrels dia. that does not risk damaging the barrel.

run a soft piece of lead through the bore (AKA slugging the bore) with a brass rod or hard wood dowel and measure the "slug" you can push a soft lead bulet through that is a little bigger than the bore.



theres a product that you melt and pour intoo the chamber to cast the chamber cerosafe, I think that would work too. It has a very low meltiung point.http://www.midwayusa.com/viewProduct/de ... ber=462291

What Bullseye said. I wanted to check the barrel in my 229 and found this tip on another forum.

If this is for a hand gun use a spent brass as a mold and melt some hot lead into it using a torch. Most all spent brass will have a slight taper and only be slightly larger than your bore. Then use an inertia bullet puller to pull the lead slug. Inspect that its a good pour, if not do it again. Clean off the slag with a file or belt sander. Using the brass as a mold puts a taper on the slug. Which makes it easy to start and since it's on a few 0.001" oversize, it will not take a lot of force to get it started. You will need to push the slug out onto a soft surface, not to damage it.

Some say to find some fishing weights that is close to your bore and use them. The ones used for rigging plastic worms are all ready bullet shape and work good too. But if you go that way make sure it's 100% lead and not alloy. Lead you will be able to mark with your finger nail easily.

Oil your barrel before you slug it so it will go through easily.

Thanks for the replies.

When using a straight wall cases as a mold for the slug, do the cases need to be re-sized? Also, in order to remove the slugs from the cases, do the cases need to be lubed?

Georgezilla wrote:Thanks for the replies.

When using a straight wall cases as a mold for the slug, do the cases need to be re-sized? Also, in order to remove the slugs from the cases, do the cases need to be lubed?

Why not just use a cast lead bullet? Maybe I am missing something, but you could hit it on the back against a hard surface to upset i and make it slightly larger and the drive it through the bore.

You do not want to resize the case, other wise it will not fill out the bore. You do not want to lube the brass, or clean one, or de-prime one. To remove the slug from the brass you need to use a kinetic bullet puller. The press type bullet puller will not work due to nothing to get a hold of.

You also do not want to use bullet that has already been sized. Most cast bullets are already pretty close to the final size, the reason not to use them. You want the bore to do all of the sizing.

I just use metal calipers to get a I.D. reading. I also have a set of dial calipers made of polymer plastic from Lyman. As long as you're careful and don't twist or gouge the inside of the barrel it's pretty hard to damage it.

R,
Bullseye.

I would have never guessed that it was safe to measure the barrel I.D. with metal calipers. I figured that metal cleaning rods are not supposed to contact the crown of a barrel, thus it must be the same situation with metal calipers. But now that I think about it, measuring the I.D. of a barrel is a much more controlled situation, and only the grooves are being contacted by the caliper.