8X57 JR Heym made February 1928

[Meinherr]

My Heym drilling has no caliber marks on the rifle barrel other than DRGM Plomb which is French for lead , Pat # 60215, serial # 3036, STMG, 2G GBP, Crown with an R on the rifle barrel. Both the S .323 and the .318 shells load and close. I was told the bore is .318. I have been offered a box of 8X57JR 360. Can I shoot that 360 version in this gun or is the case too small ?
Thanks for your help

[Axel E]

Don't even try it! Apparently your drilling is chambered for the 8x57IR with a base diameter of .470". The much slimmer 8x57R 360 with a .427" base will invariably split if fired in the larger chamber. Drillings don't handle such accidents kindly. You will most likely burst the stock if hot gas enters the firing pin hole.

[mike ford]

Meinherr,
Factory 8x57R-360 is much harder to find than 8x57IR, so you or your friend should just sell it to someone that needs it. People are often confused because the post 1911-12 proof marks are the same for both( 7,8 over 57, usually). Follow Axel's advice closely.
Mike

[Meinherr]

Thanks so much. If there is anyone one in Canada that wants the 10 RWS rounds I can forward their information as it cannot be shipped to the US. He wanted $25 for the 10 rounds plus shipping. I will get the barrel slugged as there are no caliber indications

[mike ford]

Meinherr,
You might find it informative to post photos of all the markings on your drilling. You cited the lack of marks, then described some. For instance, the STMG you mentioned means the drilling was proofed for a steel jacketed bullet, the 2G, GBP means it was proofed for a duty load of 2 grams (30.9 grains) of Rifle Flake Powder. Also the Crown R means the drilling had some type of significant work performed on it and was reproofed accordingly. Photos of other markings may reveal other similar information.
Mike

[Meinherr]

I took the Heym to my English gunsmith today and he measured the bore and confirmed that is. 317.5 . We discussed the issue of the reworking that shows on the barrel flats and the shotgun barrels are 12 g 65 MM (12 with a circle and 13/1) so it is possible that the throat was opened for .323 bullets. As I have 60 rounds of the 8X57 JR I decided to shoot that load but would an enlarged throat and neck affect the accuracy with that bullet size? It is hard to get good readable pictures of the rifle barrel. These are the other marks
Serial # 3036, Pat #60215 DRGM Crown R on rifle barrel , Crown with U and a W with a Crown , date 2/28, Witten Excelsior on the shotgun barrels , On the frame there is the serial # 3036 and a 478 but there is no 7.8 X57 anywhere on the frame or barrel flats

[mike ford]

Meinherr,
I would expect to find the 7,8/57(maybe 7.7 or 7.9) on the rifle barrel rather than the barrel flats or frame, it may be difficult to read. The crown U is the "view" proof mark which is a detailed inspection after firing a proof load. The Crown W is the mark for a choked barrel, but constriction is not shown. Whitten Excelsior is the type steel the shotguns barrels are made from. While not exactly approved, some throats were reamed for bullets larger than .318". Experience shows that if you hand load, you can use a bullet that easily fits into the neck of a fired case, even if larger than .318", such as .321 or .323 ( in the same cases, if other cases are used, they should be checked). Of course, you can always the 8x57IR ammo.
Mike

[Meinherr]

Thankyou very much