Not sure if this is correct section for this..

[pabirdman]

I have been buying some antiques,and have started to wonder about what calibre they would be.Can anyone suggest a way to measure or is there a book to read that describes how to calculate?Thanks for any help.Glen

 

[josquin]

I have been buying some antiques,and have started to wonder about what calibre they would be.Can anyone suggest a way to measure or is there a book to read that describes how to calculate?Thanks for any help.Glen

Really the only way is to slug the bore by ramming a pure lead slug through it and measuring with a micrometer. This can be esp. useful with some old guns as the bore diameter can vary by a surprising amount. (Even .303's can vary from .311- .314 or so.) There are also dedicated forums for some types, such as britishmilitariaforums.yuku.com.

If you are talking about really old guns, like flintlocks, slugging the bore is more difficult as you'd have to only run it in an inch or so then pull it it out with a screw extractor; possibly there are special "corkscrews" than can be put in the bore first and the lead poured around them (?)

It really depends on the type of gun and the age. Posting pics with any identifying marks or maker's name can sometimes be useful. I'd try posting in the "Black Powder and Antiques" section.

Stuart

 

[mooncoon]

For cartridge guns, slug the bore with a lead ball a small amount larger than the hole. Using an elongate piece of lead takes too much force for practical purposes. Also take a chamber cast and while Cerrosafe is what a gunsmith would usually use, you can get some pretty good measurements using parafin wax. Block the bore just ahead of the chamber and pour in melted wax. Let it cool and knock it out. You might try putting a piece of cotton string in the wax to keep the pieces together in case it cracks while removing.
Use a micrometer or good digital caliper to measure the base diameter, shoulder diameter, neck diameter and the length to the shoulder and total length then compare these to the published dimensions in Cartridges of the World. It is not uncommon for chambers to be a little oversize.

cheers mooncoon

 

[darxtar]

Brownells Cerrosafe. You can easily cast part of the bore and the complete chamber. Melts with a heat gun or on the stove in a double boiler. I have been using the same 1/2 pound block for years.