Anyone have an idea where I could get one?

I have a 10mm barrel, and I’ve even shot it on a semi open bolt with a 45 bolt and it worked. But if I could find a 10/40 bolt it would make me happier for the full auto.

Talk to Troy at Barrelxchange. He opens up the breech face on a standard 9mm bolt, which works pretty well. I've got barrels for my Uzi in .40 (runs great) and .357 Sig (constant nose dives) to go with my bolt.

He tends to do things in batches, so it sometimes takes a while.

The .40 runs noticably faster than 9mm.

The biggest issue I had was with mags. A .40/10mm sized cartridge doesn't stack well in an Uzi-sized mag body. I could only get 10-15 rounds in a mag, whether using a .45 mag (IMI or ProMag) or in a .41AE mag.

If you're shooting 10mm in a MAC, you're probably using grease gun mags, which seem to work great.

Thanks! I emailed him.