Barrel straightening

[30calflash]

I hope this is the place for some info. I purchased a Finnish Mosin m39 with a bent barrel some time ago. I know that barrels are straightend in the manufacturing process. I've heard of gunsmiths doing the repair also. The thought was that if I can't fix it it has a bunch of good parts. If anyone has info to pass along it would be appreciated. Thanks, Tom.

[John Traveler]

Rifle barrel straightening is not something that a casual hobbyist or even most professional gunshops can do effectively. Even the rifle barrel factories are "iffy" on their ability to straighten factory barrels. It requires a special overhead arbor press, a perfectly smooth light-reflecting bore, and an operator with many years of experience and ability. What chance does the average hobbyist or even most gunsmiths have in this effort?

[S.R.Custom]

This is one of those "depends" questions that only generates more questions... How bent is the barrel now? And how straight does it need to be after it's "fixed"? And it's also one of those things I can not offer any advice on unless I can physically examine the object.

But I can say this-- it is possible to take some bend out of a barrel with no more sophisticated set-up than two wood blocks and dead-blow hammer. And a Mosin would be the perfect piece to try your luck on.

[MBTcustom]

Hey can you get the barrel off the action? Id be willing to take a crack at it if its a last ditch effort. I would mount it in my lathe and use indicators to find the high spots. It aint nothin but a piece of 3/4" steel pipe. Bet I could get 'er pretty close.
I straitened a shotgun barrel once by building blocks up on my work bench and puttin the 'ol Arkansas on it. I lucked out and it came out great.
If your barrel is bent much, I cant imagine how I could make it worse and who knows? it might shoot fine. I will say this though, I would not go whacking it with a hammer; it was bent into its current shape and it must be bent back. Block it in with 2X4s on a solid workbench top and pull on it. That way you dont go to far and you cant put any thing in that you cant take out later.

[30calflash]

I sighted down the barrel from the action end and it has about 3" deflection down at the muzzle and about 4" left. It bent in front of the rear sight base. No kinks, dents or large dings that I could see. Looks like a shifter from a mid 40's pickup. Really.
I think it a longshot at best. What the Finn's enemies couldn't do to it the common carriers of the US did in the course of their everyday routine!
If I can get a couple pics I'll try to get them up.

[old turtle]

I think you might send it to Goodsteel and let him give it a try. His idea of checking it with a lathe sounds good to me. He is a machinist who seems to know what he is talking about. If all else fails you could get a used barrel I would think. But then, I am clueless in most things. I just saw your description of the damage and that is more than the usual bend. Might be new barrel time.

[rbertalotto]

I took a bunch of folks from my gun club to the Savage factory last year. Savage "trues" all their barrels with a very simple technic. You look through the bore at a white wall. It is amazing how easy it is to see the bend in the bore. Even if it is only a thousandth or two off. I was allowed to try my hand at straightening one. It was quite easy with the overhead press. I was told when they measure a bore with a laser device after this procedure, they were nearly perfect or as close as they could measure.

[rbertalotto]

BTW, that's not me........I'm much more handsome!

[frankenfab]

I took a bunch of folks from my gun club to the Savage factory last year. Savage "trues" all their barrels with a very simple technic. You look through the bore at a white wall. It is amazing how easy it is to see the bend in the bore. Even if it is only a thousandth or two off. I was allowed to try my hand at straightening one. It was quite easy with the overhead press. I was told when they measure a bore with a laser device after this procedure, they were nearly perfect or as close as they could measure.

That is very cool, thanks for sharing!

[30calflash]

That's the deal I've seen pics of at maybe Anschutz. There are a few things that I'll ponder before the attempt. I appreciate the replies thus far, including the offer to straighten it.
I think it would be difficult to remove the barrel at this time. Plus the added length of the receiver may help in the straightening and alignment of things. There is also a fair chance that it is bent under the sight base which would probably finish it as a repair deal. I'll get pics up this week. Thanks to all.

[John Taylor]

I have one of those inexpensive HF 12 ton presses that I use. Like the man said, look through the bore but on one with a 3" bend you ain't going to see through the bore. A couple of blocks with a half round cut out for support and another one to push with and they bend real easy. You need to go a little past center and let it spring back.

[JIMinPHX]

I spoke to a guy that had worked for Savage many years ago. The barrel straightening methods he described sounded crude at best. So did the standards for straightness that he said they employed at the time. He seemed to think that a barrel with a little bend was no big deal because as long as it shot to the same place every time, you could just adjust the sights to compensate for it. He said that back then, they only straightened the really bad ones. Rbertalotto's post makes it sound like they may have improved things since then. The one piece of valuable information that I did get off that gentleman was that they determined straightness by viewing the bore. Apparently the bore is not always concentric with the OD of the barrel, so indicating the OD is no guarantee of success.

I haven't straightened any barrels myself, but I have straightened plenty of motorcycle forks, pump shafts, impeller shafts & torque tubes. In most cases, you need 3 blocks that fit the OD of the part to be straightened & a hydraulic press with enough pressure to move the part. I concur with what John Taylor says about bending the part past straight & then bringing it back a little. If you don't do that, then you leave stress in the material & part of the bend will likely come back in time. As a rule of thumb, I usually bend most shafts & tubes about 5-10% of the original deflection past the point of being straight & then flip them over & bring them back straight.

[nanuk]

I remember reading an article by a gunsmith who straightened barrels, New and Used, using a press, for large bends, a lead hammer and lead blocks for smaller radius bends, and offset blocks and sliding the barrel in where you need, and pulling by hand on the end.

His theory was like JIMinPHX said. Barrels bend when shot anyways, as long as they are as stress free as you can make them and as straight as you can get them with the naked eye, they will shoot well.

I've never had a bent one to try, and hope I never do

[B R Shooter]

Most every MAJOR custom barrel maker will not straighten a barrel. It's not the barrel that is crooked, it's the drilled hole. You go bending the OD of the barrel to compensate for the drift in the drilled hole, then you WILL end up with a bent barrel.

A lot goes into the deep hole drilling. Of late, most barrel makers are doing a quite good job at drilling. When I put any new barrel through the headstock and dial it in, I look down the bore. At one time several years ago, it was not uncommon to see quite a bit of "wobble" in the bore while turning. No so often now days. Proper tooling of course plays a big part. But a drift in the drilling can also be caused by hard/soft parts in the steel. These barrels are after all an alloy, and the consistency can vary.

Another item on these so-called straightened barrels, I wonder if they are stress relieving them after they bend them?

[John Taylor]

I get barrels in from several different makers and some will have the bore running true to the OD and some will be off. Douglas barrels are always true because they turn the OD after it is bored to insure the bore is centered. Most barrels have the caliber marks on the end that is centered or where the drill started, this is used for the chamber end. If the muzzle end is off a little it does not matter because I turn between centers for a few passes to get the OD to match the bore. Very seldom will I see a bore that has a bend in the bore bad enough to see while looking through the bore on a new barrel. I get old rifles in with bent barrels quite often. Had one old 1886 come in that looked real bad, story was that great grand-pa used it to pry the wagon out of the mud. A lot of these old barrels are what we would call mild steel today, very soft and bend easy.

[Molly]

I once bought one of those $25 Chinese air rifles that arrived with a badly bent barrel. It would have cost nearly as much to send it back as it had cost to buy it, so I decided to try to straighten it out myself, since I couldn't do any harm. It sounds like you're in about the same boat, so you might want to give it a try. It's simple, easy, and won't cost you anything but the time.

Don't laugh, but I went out to the barn where I had a set of really heavy steps. I inserted the barrel between two of the steps, with the bent area down and closest to me. In other words, put the bend right at the edge of the step or whatever you use, and lean on it a little bit. Did this several times, until a little progress was evident. You can get a good idea of progress by noticing how far you bent it last time, and bending it just a TINY bit further next time. The trick is to make haste slowly. No point in getting rid of one bend by getting another one. Then I took it out and looked it over to judge the effect.

There was some visible improvement, so I did it again ... and again and again, until I couldn't see any bend left. Then I took it out and shot it a few times, which showed me that there was still a little bit of bend left. Back to the steps for few more LIGHT treatments and test groups. When I was done, it shot very nearly to the sights at about 20 feet, so I just moved the sights to zero it in the rest of the way.

Result: A well salvaged barrel that gave groups plenty good enough for tin cans and mice in the hay. It would never win any benchrest matches, but then, it never would have anyhow. Results were good, cost was zip, nothing expended but a little time, and I was well pleased with the outcome. If it works as well for you, good enough. If not, you haven't hurt yourself any, have you? Good luck, and let us know how it comes out.

[lreed]

I have a 95 Mauser that had a bend in the in the last foot or so in the barrel, would throw the bullet low and left, could not adjust sight to solve that, so tried streatening . A thin twenty-nine inch mauser barrel is like spring steel, used presses,lead hammers and got little results. In desperation used c-clamps and a little heat got the bore looking good,after fireing several rounds the barrel sort of went back home,crooked again,repeated the process again. but this time I hung the action on a beam tied a fifty pound weight to the muzzle, used a propane torch to heat to good sizzleing heat and let it cool slow. The bore is still streight and the rifle shoots cast with good accuracy. I will tell you up front this is a lot of doing with no guarrentee of success, worked for me but might not for you. Hope this helps. lreed

[JIMinPHX]

Near the end of WWII, the Germans made up a bunch of rifles with barrels that were bent almost like the letter U. They issued them to tankers so that they would be able to stick them through the top hatch & fend off an infantry attack without getting out of their armor box. I don't know how effective the guns were for their intended purpose, but all reports that I have heard have stated that they did shoot reliably. It sounds strange to me, but that's what I've been told. I've seen pictures of the rifles too.

[30calflash]

I once bought one of those $25 Chinese air rifles that arrived with a badly bent barrel. It would have cost nearly as much to send it back as it had cost to buy it, so I decided to try to straighten it out myself, since I couldn't do any harm. It sounds like you're in about the same boat, so you might want to give it a try. It's simple, easy, and won't cost you anything but the time.

Don't laugh, but I went out to the barn where I had a set of really heavy steps. I inserted the barrel between two of the steps, with the bent area down and closest to me. In other words, put the bend right at the edge of the step or whatever you use, and lean on it a little bit. Did this several times, until a little progress was evident. You can get a good idea of progress by noticing how far you bent it last time, and bending it just a TINY bit further next time. The trick is to make haste slowly. No point in getting rid of one bend by getting another one. Then I took it out and looked it over to judge the effect.

There was some visible improvement, so I did it again ... and again and again, until I couldn't see any bend left. Then I took it out and shot it a few times, which showed me that there was still a little bit of bend left. Back to the steps for few more LIGHT treatments and test groups. When I was done, it shot very nearly to the sights at about 20 feet, so I just moved the sights to zero it in the rest of the way.

Result: A well salvaged barrel that gave groups plenty good enough for tin cans and mice in the hay. It would never win any benchrest matches, but then, it never would have anyhow. Results were good, cost was zip, nothing expended but a little time, and I was well pleased with the outcome. If it works as well for you, good enough. If not, you haven't hurt yourself any, have you? Good luck, and let us know how it comes out.

I thought something along the same lines with possibly using a press if need be. Barrel steel is on the soft side from what I understand. I thought that once the process was underway and started getting close that a visual through the bore and maybe using a boresighter with the sights could give some indication of being close. Going slow and steady will be the WTG.
Again, thanks for all of your advise.

[jmh54738]

My thoughts regarding straightening would be the stress that results from the straightening process and how the straightened barrel will react to the heat of firing a string of shots. I believe that all barrels are stress relieved during manufacture. Ireed brings up interesting facts regarding straightening......As a tool and diemaker, sometimes a length of tool steel would warp in the heat-treat process beyond the amount of stock allowed for grinding. The young fellows tried using a press to straighten the steel with no affect. I was able to straighten the piece within .0005, that's half a thou, by setting up the piece on blocks (carbon/graphite blocks from the EDM) in a vertical mill and using the spindle to press the die section straight and without over bend. It was then slowly heated to around 450 or 500 deg F, (below the normal tempering temp) then allowed to cool. The .022" bend was reduced to .0005, and didn't warp again during finish grinding. As an example of stress in metal, just put a 6" long piece of cold rolled steel in the mill vise and mill off .062 from one side. Now check the once straight side opposite the cut and you will find it now bowed about .060 to .080 or more. Well, after all, it is cold rolled and full of stress.