Unknown gun. 75mm?

[nirvana]

Found this at a VFW post in Indiana over the weekend. It looks sort of like a 75mm gun, but it has some unusual qualities. If you look in the first two photos, there is a tube running down from the trunnion area back towards the breech at a 30 degree angle. There is a hole in the barrel here, almost like it was designed to vent some pressure towards the rear. The barrel is massive, a lot thicker than you'd expect. The mount looks scabbed together, so I don't think it goes with the gun. There is a linkage on the breech handle, that makes me think the gun was somewhat automatic? Any guesses?

[Dangerous Bob B]

It is a 3 inch 50 trainer

[nirvana]

I see the resemblance, yea. Does it have a special nomenclature? Does it fire blanks, or do anything else notable?
thank you.

[Dangerous Bob B]

Pretty sure it is just for practicing loading and unloading those wooden 3/50 shells that are everywhere.

[MASH_4077]

You must be on the back side of Ft. Benjamin in Indy! A photography company did a photo shoot there back in 2012 and I had the privilege to let them use my M38A1. But I don't remember that gun being there.

[nirvana]

Bob,
Thank you for the info. It's helpful. I had no idea what this thing was.

Mash,
You're right. They have the Sherman, an F-86, a GP bomb (250 lb?) and this gun. Was traveling through the area and decided to grab a few shots.

Thanks all.
C