What is this?

That's no modern LEO item. You have a sub-caliber chamber which allows you to shoot smaller, cheaper ammo in a larger caliber firearm. Looks like the black steel sub-caliber chamber might fit into a .45 Colt.

That’s really weird. Doesn’t look like a regular chamber adapter either. The rim looks thick and the case looks too short.

It’s not a chamber adapter per se. The rim is too thick (what cartridge would it be adapting good to? It would need to be something shotgun sized by that rim is too thick) and to be honest nobody would toss 10 of those as they are expensive. Plus why 10? I’ve only ever seen the adapters sold as sets of 1 or 6.

This is what a .38 special to .410 adapter looks like:
https://www.gunadapters.com/410-to-38-special-scavenger-series/

It seems more likely that those were .38 colt blanks set in some sort of sleeve to perhaps launch something like a teargas canister. Why .38 colt? I have no idea, maybe they were common when the thing was designed.

Perhaps something like this:

https://firearmscanada.com/ads/40mm-37mm-m203-grenade-launcher-ammo-smoke-inert-etc/

Lots of web hits on 38 short colt and grenade launchers but mostly 404 dead links.

A guy at my range had a small little top break shotgun and a small case with it that carried adapters to shoot center-fire ammunition. Similar to this

https://www.alloutdoor.com/2016/08/...ion-gun-shoot-dozen-different-calibersgauges/

It looks a lot like those caliber adapters.

Funny to see so many laying around, they weren't cheap. I remember the guy saying that the case full of adapters was $250ish..

Isn't there a muzzle loaded that uses a sleeve like that and primed or blank cases as the ignition source? Like the Remington Ultimate Muzzle Loader?

Is the cartridge normal or a crimped blank?

Better be a blank, hole out the front end looks smaller than .36".

Ed Ames said:

It seems more likely that those were .38 colt blanks set in some sort of sleeve to perhaps launch something like a teargas canister. Why .38 colt? I have no idea, maybe they were common when the thing was designed.

Click to expand...

That's my guess. Somebody found it in a old storage locker or dad's garage. That's why they disposed of the sleeves along with the empty casings. Either didn't know any better or didn't care. The new looking Starline cases is a quandary tho...........

.38 Short Colt is an obsolete, early cartridge with a heeled bullet (a smaller section that fits inside the case, like a 22 rimfire). At one time, they were quite available and probably cheap. They are no longer either. They were used in revolvers, I know of no semi-automatic in which they would shoot. From the photos, I have no idea what arm would be the larger gun.

I do know the U. S. military has (or had) such an adapter as a the 'primer' for cannon rounds. Except the 'smaller' round was a blank .38 Special made to set off the cannon round (155mm towed howitzer). Don't know what earlier ones might have been.

The outer section looks like a chamber adapter, to fire the (presumably cheaper and less recoiling round) in a larger arm in place of the more expensive and harsh recoiling round. However to be effective in such manner, the 'larger' arm would have to be functionally the same bore diameter as the smaller round (I believe one can still get an adapter to fire .32 ACP ammunition in a .30-06 rifle; at one time they were plentiful).

Likely these were thrown away in the belief they were worthless, the cartridge and arm for which they were made no longer popular or in use. But a collector of the old gun in question might be interested from a collector standpoint. Or a cartridge collector.

This has been bugging me since last evening. I have seen those adaptors before. They are for a .38 short Colt blank to fire a practice grenade or something similar. The only reason I even know that is I found some of those at a range in Norco CA years ago and a LA Sheriff Deputy friend told me that they were for training rounds for a grenade launcher but that was all I remembered.

I found this document that discusses using .38 short Colt blanks in training rounds. Do a word search for “blank” and you will see various uses for the blank adaptors in different launchers.
https://www.prc68.com/I/40mm.shtml

Hope this helps

Hope you find out and let all know EXACTLY what those are and how old are they ?.