I am contemplating building a .500 J on a Brno 602 action.

I have this .50 MG barrel (QCB), is it usable for this project...I have no idea about barrel twist etc.

I have cut off the hard-metal part on it..

Anyone..?

The bore and groove are right for it, and the twist should be 1:15" for the milsurp,
also very good.

I bought one of those barrels once, at a Knob Creek Machinegun Shoot/gun show.

Some of the rifling was missing inside mine.

Rip

If I was going to go through the trouble. I would not waste the time with a unknown surplus MG barrel.

I am a real fugal guy but being cheap can end up costing you more instead of doing it right the first time.

When yo say you cut off the hard part what are you referring to. Many of the Ma Deuce barrels were Stelite lined. VERY HARD!

IIRC the very first .50 Alaskan was built using an M2 barrel. I don't think he was worried about range. He also cut off steel cored .50 BMG bullets, inverted the base like a truncated cone and loaded them.

I cut about 5 inches ahead of the chamber..

The MG barrels were not known for real accuracy even with the best of bullets. Turning them down may also result in a even looser barrel. Twist is fine but I'd strongly suggest you buy a better barrel.

it would work, "okay" .. a friend had one on a 500a2, and i have that barrel now .. the bore is/was nor true, but the machining of the contour is.. the gun shot pretty well ---

just letting you know it CAN be done, though the machining cost may make the project cheaper if you get a new barrel ....

UNLESS norway is a country where the barrel is the serialized part

Hmmm...okay...a friend built a .500 A-Square on a similar barrel, works like a charm..

You never know, you might do fine. Keep in mind though the Ma Deuce was intended to produce a cone of fire. That's how all MGs work. Single round precision is not on the list of requirements. It's your build, go for it. The worst that can happen is poor accuracy and some wasted money.

Turning a Ma Deuce down to sporter rifle dimentions could introduce a lot of stresses in the barrel. As has been stated the M2 barrels were not meant for great accuracy.
No 50 BMG TARGET rifle shooters would think of using those barrels if they want an accurate barrel. I have a Windrunner and 2 McMillan bench guns and certainly would not use those barrels.