barrel straightening

[infideleggwelder]

have an antique smoothbore barrel that is slightly bent. it is octagon to round with a wedding band. I`m talking very slightly, but I can see it. when a straight edge is held to it, on one side there is no gaps, but directly opposite, there is a gap beginning at the wedding band and gently arcs to the muzzle. it might be 1/16 max, probably less. how do I straighten this out?

 

[Dogleg]

Hit it with a hammer.

 

[hunter5425]

Take to a gunsmith, with a press and dial indicator he can return the outside of the barrel to straight.

 

[dan belisle]

Barrel press will straighten it (Google it for a picture), not too hard to make your own either. Dial indicators are good, but if you set it up so that you can see through it while you're pressing you can do it by eye (watch the light circle). - dan

 

[diopter]

https://www.canadiangunnutz.com/forum/showthread.php/751225-Brit-Krummlauf?highlight=Krummlauf

 

[infideleggwelder]

Thanks for the info. I guess that it being thinner walled I`d just need to be more careful. it is not worth the money that I`d have to pay a "smith" around here

 

[diopter]

Remember that you have to bend it a bit past straight due to metal rebounding back.

 

[yomomma]

Straightened my shotgun with a rubber tire...truth

 

[guntech]

have an antique smoothbore barrel that is slightly bent. it is octagon to round with a wedding band. I`m talking very slightly, but I can see it. when a straight edge is held to it, on one side there is no gaps, but directly opposite, there is a gap beginning at the wedding band and gently arcs to the muzzle. it might be 1/16 max, probably less. how do I straighten this out?

Maybe it needs to be bent... where is the point of impact in relation to your aim? I have seen trap shooters bend their smooth bore to shoot where they want it to... and it works...

 

[mooncoon]

have an antique smoothbore barrel that is slightly bent. it is octagon to round with a wedding band. I`m talking very slightly, but I can see it. when a straight edge is held to it, on one side there is no gaps, but directly opposite, there is a gap beginning at the wedding band and gently arcs to the muzzle. it might be 1/16 max, probably less. how do I straighten this out?

I would start with a couple of wooden cradles to go under the barrel ; short pieces of wood about 6" long and 2 or 3'" wide and 1" thick with a half round rasped on the top side to cradle the barrel. Make another for the top of the barrel and finally a long tapered wedge starting at 1/4" thick tapering to 1" at the big end. Lay the barrel in the cradles with the rear one just ahead of the wedding band.. You need a ridged piece to clamp against and use a large C clamp with the third "cradle" on the top of the barrel at the middle of the bend. The long tapered wood wedge is to allow you to measure how far you are bending the barrel down; slide the wood under the barrel with no pressure on the barrel and mark how far under it goes then remove the wedge bend the barrel down a bit, measure and mark how far down you are then take the pressure off and use the wedge to see if you made any lasting difference. Be careful because some barrels are dead soft while others are quite springy. Just keep clamping down a bit more each time until the barrel is straight

cheers mooncoon

 

[David Henry]

Just because it looks like the barrel has a slight bow or bend on the outside when a straight edge is applied doesn't mean the bore will follow suit. Often in smooth bore manufacture the I.D. is tended to first and then the O.D. is final turned and polished which can remove material in spots not concentric to the bore. Its not hard to tell if a barrel is bent, clean the inside until you get it as shinny as possible and look at a light source, many suggest a light bulb. Walk the light source around the periphery of the inside of the barrel wall. if every shadow is symmetrical in 360 degrees your good if not you have a bend. I know you may not have looked down many barrels and there's no substitute for countless years of service at some viewing room in a proof house or barrel shop but at least you will get a feel for it if you take your time. D.H.

 

[Ganderite]

I have bent a number of barrels. Put the gun across the front of an ATV in fork rests. Hit a tree with the muzzle end of the barrel. Works evry time....

 

[Ol' Flinter]

Dave Henry is absolutely correct, as is Guntech. Looking down the bore is the only true way to determine if a barrel is crooked. Also, it was not uncommon for owners of NW Trade Guns and the like to bend their barrels upward or wherever slightly to achieve the desired point of impact. I strongly suggest that you shoot it first to determine the point of impact as it may in fact be right where it should be rather than off to one side.

 

[infideleggwelder]

all good advice, especially Ganderite`s.....lol
I`ll hold off on it for now, it is for a project that requires a lot of work. I`ve looked down the barrel and it does not seem bent inside. Before I re-stock it, I`ll set it up for a test fire and see where the MPI is.

as an aside, the "bent" side`s wall thickness is thicker than the straight side as well

 

[mooncoon]

here are some photos of the method that I use. The barrel is from a New Model 1863 Percussion Sharps rifle. The long wooden wedge is how I measure the degree of flex when clamping down and how much of that is retained after the clamp is loosened off.
The base that I am clamping against is a piece of 1" stainless scrap and I also marked the top of the bend with soapstone before setting it up for clamping. Very easy to forget exactly where you feel the bend is, while setting up

cheers mooncoon

 

[SIGP2101]

mooncoon, what is on the other end of that C-clamp screw?
If you find the way to attach forklift steering wheel with knob you will gain more precise control and ease whole process of straightening barrels..

 

[guntech]

I tried bending an Italian reproduction large caliber barrel... a 45-70 I think... it had a gentle very slight curve to it but was like a truck spring... with hundreds of pounds I could bend the muzzle off plane about 8 inches and it would spring right back... I couldn't increase the pressure and gave up...

 

[mooncoon]

mooncoon, what is on the other end of that C-clamp screw?
If you find the way to attach forklift steering wheel with knob you will gain more precise control and ease whole process of straightening barrels..

I just turn the screw with my fingers. There is a fair amount of guess work in deciding how much to bend a barrel and guessing how much it will return. As guntech mentions, there is a lot of variation from one barrel to the next in how springy they are and you have to try a bit and if it is not enough, try a bit more until you have the right amount. The purpose of the wedge is that it is a cheap and dirty way of measuring the amount of flex and without a way of measuring how much you have bent the barrel (down) it is very difficult to consistently increase the amount of bending by a small amount. I think that I have straightened 4 or 5 barrel so far, over a period of several years and those because I mostly play with antique guns which have lead a hard life (which is why I can almost afford them ). If my memory is correct, the barrel in the photos was very soft (probably made of wrought iron) and I overshot and had to come back a bit. I must have done something right because while the gun is by no means spectacularly accurate, it does group more or less in line with the centerline of the barrel. The accuracy problem is in part a result of a significant amount of pitting in the first 3 or 4 inches ahead of the "chamber"

cheers mooncoon