.308 Win to .30 Carbine sub-calibre adaptor

I don’t know what this is supposed to shoot. It closely resembles .308 which I provide for comparison. There is nothing written on it. What is it?

Could chamber the following calibers:

30 Mauser
32 ACP
30 Luger
30 Carbine
32 colt short, long, H&R

etc… to name a few…

Here is a company that make the chamber adapters:


I think we can exclude rimmed or semi rimmed cases to be used with this adaptor (if it is one at all) as there is no recess in the base section.

Vlad, can you check if there is a step inside the case located at c. 33 mm from the rim?

Or just shove in a .30 carbine round and see how it fits…

Actually, Alex’s suggestion worked very well, .30 Carbine sits very snuggly. So, this is probably .308 to shoot .30 Carbine adaptor. And, yes, Fede, there appears to be a step-up at about 33mm.

Vlad, then you have a type of .308 adapter for .30 Carbine cartridges that was first distributed in the States by Sport Specialty of Kodiak, Alaska. These were made in Germany by Lothar Walther but this fact was only mentioned in early ads from 1969-70; after this date the company moved to California and changed its designation several times (Owen Specialties; Sport Specialties; Harry Owen) and the manufacturer of these adaptors was not indicated anymore. However, I don’t have any indication confirming that this company has manufactured any of these. It still advertised these in the mid-1990’s.

This ad was published August 1970:

The products offered under the current company designation (since c. 1999 MCA Sports/Ace Bullet Company) seems to be indeed of US manufacture.

Be a little cautious when using one of these. I have collected quite a few of these over the years and used one in 32 ACP X 30-06 to finish of an antelope. The adapter refused to be extracted and it took 3 attempts using chamber casting allow poured into the chamber to finally get the dang thing out of the chamber of my pre 64 model 70. While other I have used over the years have had extraction and chambering issues as well. My suggestion would be to oil it well, then check to see it it chambers and extracts well enough before use.