Barrel profiling question

[DShortt]

So. I set up a dead center in my lathe headstock. Then set up a dead center in my tailstock and matched them.

Then moved the tailstock back to the barrel length and inserted a barrel blank between the 2. Mounted a dial indicator on the carriage and checked the run-out.

Don't ever do that unless you’ve an affinity for nightmares.

Just sayin'.

I freely admit there are multiple possible sources for the results that I saw. Just curious if anyone else has tried this?

 

[Doug Beach]

Some things are best left unexamined.
I chambered a barrel that had a distinct curve, about .050” TIR, in the center of the blank. It shot great.

 

[Will Henry]

Most blanks will be a little crooked. Many of the makers will straighten after drilling, before reaming. Naturally, this results in a curvature of the outside. In addition, it's a rarity that the hole is perfectly centered. WH

 

[LVLAaron]

Sure. The ID of the bore is never going to match the OD of the barrel.

 

[AccelR8]

Sometimes I get unturned "gunsmith addition" blanks from a certain supplier. I center drill both ends with a piloted center reamer, then turn the profile between centers.

"Interrupted cut" is a mild description of the process

 

[Jonnyofalltrades]

I have done this. Scared me at first, but you sort of get used to the reality that nothing is straight, ever. The longer a part is, the more you notice it.

 

[DShortt]

The thing that really grabbed my attention wasn't the run-out in the center area of the span. It was the run-out at the extreme ends.

That's not easily explained away.

If the bore ID doesn’t match the barrel OD at the chamber or muzzle, I can't imagine anything good resulting from that unless.you subscribe to 'spontaneous serendipity'.

 

[AccelR8]

The thing that really grabbed my attention wasn't the run-out in the center area of the span. It was the run-out at the extreme ends.

That's not easily explained away.

If the bore ID doesn’t match the barrel OD at the chamber or muzzle, I can't imagine anything good resulting from that unless.you subscribe to 'spontaneous serendipity'.

Those unturned blanks I've had, I find one end where they stared the drill, the bore is centered pretty well but the other end can be off a bit. Never been horrible, and not always visible at a quick glance. Often have to measure if you want to know. On the other hand yours was a blank that had been contoured or turned between centers, I would wonder about that.