Q: I have been given an old military rifle of European make which does not have the maker’s name or the calibre marked on it anywhere. It is a bolt-action which my gunsmith does not recognise. The rifle’s bore and the action are in reasonable condition and I’d like to try shooting it.
My gunsmith suggested that the only way to find out what cartridge this rifle is chambered for is to get a chamber cast made.
How do I go about it? What can you tell me about making a chamber cast?
George Montgomery
A: Don’t try to make the chamber cast yourself; ask your gunsmith to do it.
After I obtained an M17 rifle chambered for the .30 Newton, gunsmith Rob Spittles made a cast of the chamber in order to determine the chamber dimensions and throat length.
Some of the older American guns were never marked or else wear obliterated the original markings. I believe Model 1876 Winchesters were bad offenders in this respect, since calibre markings were stamped on the soft brass cartridge carrier where in time they were worn off.
In the case of European weapons, there may be several reasons why they have no markings. Thousands of small gun shops rebuilt military rifles without giving any thought to applying marks, not even their own names.
Military rifles were frequently left unmarked even if the calibre was changed by reboring or rechambering.
Before you can buy ammunition or make some, you must determine the calibre. In some instances it may be possible to do this by taking a few measurements from the chamber and bore, but this can sometimes be misleading. The best solution is to make a cast of the chamber from which all the dimensions of the chamber can be measured precisely.
I could give you a recipe to do the job, but several casting compounds are available from various sources which produce a better result.
Once your gunsmith has made a cast, its dimensions can be measured and a comparison made from listed cartridge data, using a book like Cartridges of The World as a guide.
Once you have these measurements it should be easy to match the cast with one of the cartridges listed in this or any other reference book and the correct calibre designation will be evident.
Bullet diameter may also be determined by measuring that portion of the cast which extends into the rifling, that’s if the cast filled out completely to the bottom of the grooves.
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