Could someone tell me what this is?

fist guess a bomb. looks interesting but I just don't know

Looks like some kind of kinetic bullet puller.

Maybe it's a lube canister for a bullet sizer?

I don't think it has anything at all to do with .308 reloading.
And it certainly isn't a bullet puller.

Looks like the business end off a grease gun for lubing machinery, or a water trap off an air compressor then anything else I can thing of.

Does it unscrew in the middle where the seam is?

rc

Well It's not a bomb. It does resemble a water separator to some degree as RC stated

Hydraulic Berdan deprimer maybe?

did it have any kind of residue inside? or an odor? like some kind of lubricant.

neck expander?

I'm new to reloading but a guy at work has been reloading for many years. He doesn't know what it is either. Maybe some kind of neck seizer???

Are the two black rings gaskets? Is the disc with two holes in it spring loaded or fixed in place? Are the two halves being held together somehow in your OP or are they just stacked? Both halves have female threads. Was there any kind of threaded coupling in the box?

My dad was a machinist, and maybe this is totally unrelated to loading.

Click to expand...

In that case it looks to be a very heavy duty nut cracker.

show some 308 brass beside it for perspective

I think it's a C02 cartridge holder/piercer for making your own fizzy beverages!!

rc

No holes on the bottom? It sure looks like a 'squeezer' of some sort, maybe it would fit a Co2 cartridge as RC mentioned?

Uhm, maybe it is a whippet dispenser.

Search n20 cracker on google. I seem to recall(kind of fuzzily) that folks could get the same size cartridges for laughing gas and take shots of it, for entertainment purposes. The tool(?) for doing that looks very similar.

You need to show us the other end of the bottom piece. Also, the bottom screws into something else, still.

What I see so far is that air (or oil or water) probably goes in one bottom hole and out the other. The screw determines how much....that is if the tapered part of the screw screws into a matching machined female orifice, that will close totally when screwed all the way in. We will know that when we see the other end of the bottom piece. If so, it's probably a pressure valve. jmorris could probably MAKE it into a reloading tool.:

Looks like it might be some sort of pressure regulator. There is something missing from your photos but the adjustment you show likely pushes on a diaphragm and the little hole to the outside bleeds off if you have it set high then adjust to lower pressure, without flow.