I've been working on a project that was going quite well until today. This project started off as a Stainless .50 Cal muzzle loader barrel for a T/C Encore. I bored out the breach end, reamed it to .750, and threaded it 13/16 x 20. Then I parted off the barrel, leaving the stub 2 1/2" long. The barrel was threaded to match the stub (an annoying 50 turns to full lock).

Yesterday, I chambered the barrel for 50-70 Government. Today, I cut the extractor slot (1/4" wide).

In preparation for bead blasting I'd put some 6x48 screws into the scope base holes. These holes are now all the way through the internal threads in the stub. All threads had previously been chased to assure smooth connections. One of the screws had been bearing down on the barrel threads, and I marred them slightly when removing the barrel to finish the extractor slot.

When reassembling the barrel for bead blasting, I clamped the stub in my vise by the lug, and clamped on my barrel vise for some added leverage, since the barrel no longer spun on freely. All was fine until I got to that same damn screw which I had never removed. Stupid, Stupid, Stupid! The effort required to turn the barrel gradually increased. I remembered to remove the 6x48 screws. The turning effort continued to increase. The barrel vise only offers about 4" leverage on either side the the barrel CL, so I added a pair of crescent wrenches to the barrel vise and turned until seriously stuck. Attempting to back out didn't work either.

It now occurs to me that the extractor slot has the geometry of a cutting tool at the thread OD. I should have chamfered the OD. If this slot springs at all, it would bite into the inner threads of the stub. I have applied kroil, which is flowing slowly through the threads. The barrel can now be rocked back and forth about 20 degrees by hand, and about 35 degrees with the wrenches. The ends of the 35 degrees of motion stop with a very solid feel. The extractor slot is about 35 degrees at the thread OD. I can't see anything bad looking in about an inch from the breach end.

At this point, I'm considering making a Big wrench to torque the stub after the vise is screwed to the workbench. If I can get it apart, I can chase all the threads again. With 2 1/2" at 20 TPI, a little slop won't hurt anything. I'm just afraid it will continue to get worse. If I was sure I could cut the stub off, and save the barrel, that would be on the table, since I have another one of these Encore barrels to sacrifice.

I'll welcome any suggestions, and accept whatever criticism I'm due.

You know what you have to do; you only have two choices; horse it on, or off. Take your pick. If you are lucky the threads will iron out the burrs.

Any idea how much torque a ER 40 collet can hold at ~.88"? It would be a lot faster to chuck the stub up in the four jaw, hold the barrel in the tailstock, and engage the clutch at 15 RPM. (16 x 54 Pacemaker w/ amps to make 5 HP)

I think (hope) it ain't as bad as you feel it is. So it might spin right in/out.
Or not;
I would do it by hand as under power things can go bad, quick.
Can you drill out the screw, bigger, and put in an 8x40 later?

If I understand correctly, you could bore out the stub from the chamber end to .75" diameter. You will loose 2.5 " of barrel, but you get to regroup and do it right. Your intent was clearly to make a carbine. Never admit to a mistake. Just incorporate it into the design!

The four scope base screws came out quite nicely. At the moment, the extractor slot is about 90 degrees from the screw holes. I can't see anything bad through the screw holes, but was thinking that when I get the sharp edge of the slot back to the next hole (1 or 2 turns), I can knock the high points off the threads at the edge of the slot with a small end mill. The holes may be enlarged then.

I really don't want to make the barrel shorter. I like it where it is, and the reamer has to go back today. I'm headed out of town for the week, and can't work on it now anyway.

Sometimes when a thread is damaged and binding you can hold the barrel by hand with the receiver not supported and hit the receiver with a plastic hammer all the way around. Then turn the barrel until it is snug and repeat the process. With luck this will iron out the rough spots in the thread.
This has worked for me many times, it just takes a lot of patience.

Thanks.
Wayne

Stainless on stainless is a recipe for disaster.

quote:

Stainless on stainless is a recipe for disaster.

And so it was.
I twisted the barrel off just outside the stub.
If I can figure out how to center the stub in the four jaw without much of a datum, it may be salvageable. The barrel lost about 1-1/2" if I can successfully pick up the existing thread.

Feet up. Beer open. Tomorrow's another day.

I keep anti-seize compound on the shelf just for stainless on stainless jobs, and have learned (the hard way) to never even try a thread fit without it.

I work in the water and wastewater industry where most fittings today are stainless steel, antiseize just second nature when it comes to threads, you miss it you seize it.