So what do you do when a barrel warps during contouring? I'm assuming it would be from stress in the blank, heat while cutting, or both. Looking up the bore from the chamber end, only about 2/3 of the muzzle is visible.

Throw the barrel away and start fresh? Is there some "old timers" trick for straightening a barrel? Note that the barrel has already been installed and chambered, so I'm VERY hesitant to yank it and throw it away!

Any tips before I start crying?

[ 06-30-2002, 18:14: Message edited by: SamB ]

Not that I recommend this, but I once saw a guy stick his shotgun barrel between two boards nailed a few inches apart & "lean" on it till it "looked straight enough"!

On a rifle barrel expected to give good accuracy, I'm afraid I'd have to get a fresh barrel & start over. Sorry.

Not a gunsmith, but I used to do a ton of metal fabrication (built race cars)...And I would be REALLY scared to use a barrel, that warped noticably during contouring...I would say it means there's something really wrong with the metal...Or you got it EXTREMELY hot (and I can't imagine getting that hot during machining)and all hardness is gone (annealed)...In any case I wouldn't dream of shooting the thing, with that barrel, no matter what...

tomato stake, sorry pal.
the barrel might have come to you off center-bore.. and no barrel is perfectly straight. but, if it's a boomarang, it's a gardening tool
jeff

If the outside is straight, and the inside is not, if you straighten the barrel in a press to get a good bore, you will have a bent barrel outside. It sounds best as mentioned,tomato stake. Check the bore before doing any contour work on the next one. I have found some shotgun blanks that did need slight straightening before cuttin the outside.
Good luck.
Ed

Shoot it and see if it works!!

SamB----

Sorry to be a bearer of sad tidings. The barrel is ruined.

A barrel can't be turned between centers for long before it grows from heat, but it's captured between fixed points. It *has* to bend. Once bent it's pretty much junk.

The tailstock should be spring or hydraulicly adjustable to compensate for heat growth OR one end held in a steady rest while being profiled.

You might try this: I recently bought a cheap barrel from GP Corp. for a Martini project I'm working on. When I got it, I found out why it was cheap-a corkscrew. However, it -was- for an experiment, so I didn't want to invest a lot of dough. Made me a hand "brakeover" type press affair out of some angle iron, screwed it down to the workbench. Set the bbl up on a couple of "Vee" blocks, set up a couple of indicators and went to work on it. After working with it a while, got the indicators close, so went to the old "eyeball" method, holding it up to the window, and checking the shadow lines of the window mullions. Worked on it some more, and danged if I didn't get the thing where it -looks- straight. Now, I haven't shot this thing yet, so no idea if I really did any good. But I got it good enough for my 'spearmint'! Now this was a very lightweight profile bbl, and was -relatively- easy to bend. On a more standard bbl, I suspect you'd need a hydralic press. Also, the bore was reasonably straight with the outside profile. If the bore's off center, well, it's probably SOL time.

Actually I believe most pellet rifle barrels are "straightened" before being shipped to the owner. But of course we are talking a very thin and insignificant barrel compared to a real hi powered rifle barrel. I'm out of my depth here and will admit as much.

Oh well, thanks for the replies fellas...

It finally occurred to me that, as another poster pointed out, if the inside of the barrel was straighted then the outside would look bent. Duh! Be glad I don't work on the space shuttle.

The barrel will be pulled and assigned to garden duty. I tried cutting it back in sections, to see if I could shorten it past the point of the bend. I finally got it to look somewhat straight, but ended up with a 17.5" barrel. This might not have been too terrible, but see the picture below and you'll see how offset the crown would have looked.

On the right is the original crown, on the left is the last section I cut.

Mauser 98's are subjected to barrel straightening. The operator uses a rig
like a benchvise but the turning handle is like the steering wheel of a boat
and it rotates on the horizontal plane, the whole thing is pretty much above
the operator's head. The only instrument for checking straightness are the
operator's eyes. The operation is done right after the bore-hole is drilled.

If you have the book "Backbone of the Wehrmacht", it's on page 96-97.

[ 07-01-2002, 03:17: Message edited by: Pyrotek ]

The barrel bent due to stress in the barrel. In other words, the barrel had not been properly stress relieved after manufacture and may not have been done at all. It is unlikely that a barrel could bend enough from elongation while between centers to stay that way. You have to bow a barrel quite a bit to get it to take a "set". Any of the barrels from good makers are well strees relieved. Indeed the buttoned barrels must be or they won't hold dimension when they are contoured. I have had some barrels in the past that walked as soon as I started turning on them. The best cure seemed to be to put them in the oven as hot as it would go for a couple of hours. Since most of these barrels were carbon manganese this temperature appeared to be adequate to vastly improve the stability of the barrel. It would probably not be enough for chrome moly.
Surprisingly, the hammer forged barrels seem to be quite stress free. perhaps due to the high temperature of manufacture.
Where the lack of stress relief really rears it's ugly head is when a gunsmith is attempting to make a complex shape such as a half octagon with rib etc. Regards, Bill.