Barrel bending.

[patchbox]

I have a rifle with a 42",36 cal.,13/16",Green Mtn.barrel. At the 25yd. range I got it to print a nice 3/4" group about 3" to the right of center. By drifting the rear sight to the left untile it looked odd then the front sight to the right till it was noticable I got it to center on the bull. The fact that the sights are so off center bothers me.I remember reading somewhere that bending a barrel will change the POI. I'm a coward when it comes to anything that sounds that drastic so any information that  I could get on the subject would be greatly appreciated.......Chuck P.

[T*O*F]

First off, one does not bend a barrel.......one straightens a bent barrel.
Your first testt is to determine if your barrel is indeed bent and causing your problem.  Then proceed accordingly.

One can use the reflected light method, or the taut thread method.  Both require debreeching the barrel.

While the barrel is out, also check to see if the barrel channel has warped and is putting pressure on the barrel.  Long 13/16" barrels are pretty whippy.

[Scott Bumpus]

One option is to make a new rear sight with the notch offset.  It gives the same effect but does not look funky.  First i would pull the barrel and make sure there are not any issues with stock making it shoot left or right.

[Birddog6]

I would send it back to Grn. Mtn. and have them check it. Good chance it is bored in a roc from too much pressure on a dull bit. I had one like that one time. It was allot worse than you hae, but regardless it was way off.  Sent it to Colerain & they replaced it.

Keith

[chris laubach]

Had the same problem last week with a 50 cal Green Mtn barrel. Had two 4x4 posts that where positioned perfectly. Put the barrel between the posts and gave it a pull. Working my way from muzzle to breech. Put the gun back together and went out and shot it. Found that it needed a little more bending. Took gun apart and gave it another tug, again working my way from muzzle to breech. Sights are now centered on the barrel and gun shoots where it needs too.



Chris Laubach

[smshea]

When it comes to barrels.....whatever Chris says!

[Lucky R A]

    I make a couple of wooden blocks with an octagon shape cut out in the center of them.  From the bottom of the octagon cut out to the bottom of the block is about 1/2".  I lay these on the floor of my shop.  After determining which way the barrel needs to be bent, I place the barrel onto the blocks so it is supported at both ends.  I then just step up onto the barrel, putting more and more weight onto the barrel until it bends enough to make it shoot where you want it.  I do it this way because i am heavier than Chris is strong.  This also prevents the possibility of overbending and kinking a barrel  which would be really hard to do.  It is a "bend and try" process, unless you are a mathematical genius with sophisticated measuring equipment...but then you probably wouldn't be making muzzleloaders.

[Don Getz]

We do the same thing as Lucky states above, but use an arbor press to do it.   Basically flexing the barrel from end to end
until it moves.   For Dave, we do "bend" a barrel, we sometimes jokingly call it "bending it straight".    If, after removing
the breech plug, and running a patch thru the barrel to get it nice and bright, if you look thru the barrel  you wll see some
reflective rings in the barrel.   If the muzzle end is not centered in those rings you can tell which way it is bent, this helps
when you go to straighten or bend it.   Years ago whenever Joe Wood would have a gun built with a low front sight, which he  liked, if it did not shoot to that point of aim, he would send it to us to bend so that it would to that point of aim.
It would sometimes take several sessions to achieve that........Don

[davec2]

Don,

I remember reading an article a few years ago about machining a little device (out of plastic, brass, etc.) that was fitted to the bore and would slide a short way into the end of a barrel to help check it for straightness.  The device had a small (i.e. 1/32 to 1/16 inch) hole through it.  When you looked through the other end of the barrel, the light coming through the small hole would accentuate the reflective rings you talked about and the small hole gave a more pronounced "center" to judge the straightness by.  Have you ever used anything like this and is it any easier than just looking through the clean bore?  Thanks.

Dave C

[Don Getz]

Dave......I can recall doing that, but, since it worked OK to just look thru the barrel, that is the way we ended up doing it.
For some reason, some people can look thru a barrel and not see those rings.   I guess it might just require a trained eye to do it...........Don

[Acer Saccharum]

Dave......I can recall doing that, but, since it worked OK to just look thru the barrel, that is the way we ended up doing it.
For some reason, some people can look thru a barrel and not see those rings.   I guess it might just require a trained eye to do it...........Don

It may depend on the light, Don. If you gave a disbeliever a smoothbore barrel to look thru, the scales may be lifted from their eyes. I bet they look at the rifling details, and cannot see the reflections for the grooves. Once they 'get it', they will always understand what to look for.

[Roger Fisher]

My 28 Ga smoothy shooter shot low at 30yds rest  and after taking the frt sight down to a mere nub (no rear sight)  I bent the thing 'up' using a heavy plank a combo of blocks - shims - and big C clamps.  Really squeezed the bejebers out of it and noticed she went back in to the stock 'different'   She was then shooting where I wanted!  Happy day!

[Acer Saccharum]

Watch bending barrels that have lugs dovetailed in. That's where most of the bend will take place...the weakest place.

Tom