Bent Barrel?

[Kraschenbirn]

A few years ago, I acquired a badly 'bubba'd' VZ-24 with all matching numbers on the bolt/receiver/floorplate. As I didn't have that much invested...$50 or so, as I recall...I figured I could invest a bit of time rehabbing it into a 'knock-around' rifle and have been tinkering with it, off and on, for the last couple of winters.

Now that the work, for the most part, is completed, I've discovered that the gun has something of a problem. No matter what I do, it shoots way to the right of POA. Like I've got the windage knob on that Lyman 48M cranked all the way to the left and it's still shoots 6" right @ 100M. Yeah, before anyone asks, the rear sight is correctly mounted and tight on the receiver and the Williams front ramp is properly aligned. Also, the barrel is free-floated with a freshly crowned muzzle. Bore is bright with sharp lands/grooves and slugs at .3235. Yesterday, I shot a sub-2", 10-shot group at 100M (Lee 329-205 over 28.5 gr. Varget) but it was centered at 4 o'clock in the 6-ring of an MR-52 target.

This isn't the first rifle I've rebuilt (or built up from a barreled action) but I've pretty well exhausted everything I can think of. I'm beginning to believe I'm dealing with a bent/distorted barrel but have no idea how to check or measure to verify or disprove that theory. (1) Any suggestions? (2) Can a 'bent' barrel be corrected? If so, I'm open to suggestions or learning from others' previous experience.

Bill

[ilcop22]

Have you shot any mil-spec or surplus loads, or have you only been shooting cast/hand loads?

[405]

By bore sighting with great care you should be able to detect any large difference between bore line and sight line. Now, whether or not that translates into POI in a particular direction?- who knows. Every slightly bent or warped barrel I've been around was a real bugger!! They did not tend to shoot in some particular direction though. They tended to just be lousy shooters- yielding large random groups. Human nature dictates that, while in a state of denial, most will try every other option/remedy to make a gun shoot.... THEN check for barrel straightness last. One way and maybe not the best or only way to check is to put barrel between cone centers on a lathe and spin. Visible wobble of the OD edge (especially of the middle third of the barrel) will be very apparent. Any wobble is not a good thing!

[Me not you]

If you're shooting decent groups, it's probably the load. A lot of rifles will drift the point of impact from one side to the other as velocity changes. Try some heavier loads and see what that does.

[Kraschenbirn]

ilcop22: "Have you shot any mil-spec or surplus loads, or have you only been shooting cast/hand loads?"

Yup! Have tried both milsurp and factory JSPs...same results. Actually, though, my CB loads group better than either.


405: "Human nature dictates that, while in a state of denial, most will try every other option/remedy to make a gun shoot.... THEN check for barrel straightness last."

No argument from me on that point. I've pretty well exhausted my repetoire of 'fixes' and was already considering what you suggested - rotating the barrelled action between a pair of live centers and checking for runout - but I don't have a lathe and haven't had a chance to make it out to a friend's tool & die shop yet.

I probably wouldn't have expended so much effort but the darn thing groups with cast as well as any of my factory guns and, except for my S-Rs, better than any milsurp I own. Guess I may have to start shopping around for another barrel.

Bill

[flounderman]

I just had a jap with a bent barrel. bore sighted it and couldn't hit the target. when I got it on the paper and checked the bore sight again, it was about 5 feet off at 200 yards. I cut the barrel back 6 inches or so, and crowned it and it bore sights where it shoots, now. you should be able to lay the barrel on a flat surface and see if it is crooked by rotating it. you might straighten it with a hydralic jack.

[Pavogrande]

If I recall, the old in shop way to check for a bent barrel was to look through it at a fairly strong light. If it is bent the the circles you see will not be concentric.

[Gtek]

Cheap and easy- take barreled action out. Cut 2x4 to length 1/2" shorter than barrel from muzzle to receiver face. Cut 1/4" ply to nail/screw to end with V cuts. Lay barrel/rec on and roll. If you do not have dials of any kind, just stack something to almost touching at middle point. They can be straightened and have done so, but sometimes still have pooch when done. Low end barrels are less than a buck new, used you can sometimes find pretty nice used for half that. Gtek

[scb]

This is how a barrel is straightened properly.
http://www.nij.gov/training/firearms-training/embed_swf.htm?link=images/videos.swf&flvLink=module04/images/fir_m04_t06_04.flv&slides=0
This shows the problem with attempting to straighten a barrel by looking at the out side of it.
http://www.massbayengineering.com/Downloads/AccuBore%20Flyer%202012-01-11.pdf

[405]

No argument from me on that point. I've pretty well exhausted my repetoire of 'fixes' and was already considering what you suggested - rotating the barrelled action between a pair of live centers and checking for runout - but I don't have a lathe and haven't had a chance to make it out to a friend's tool & die shop yet.



I'm in the same boat but do have access to a friend's high end lathe and milling machine- for which I'm very grateful!

As has been posted, the roll-across-perfectly-flat-rails method can also show a warp or bend. Since it is shooting decent to better groups, I doubt it is bent or warped very much and the excess sighting windage may have more to do with something else. One possibility is barrel was bored off axis. A way to check that is again in a lathe between centers. With off axis bore, the runout will either be uniform for the length of the barrel or for sure at either end. A dial indicator placed near the end of the barrel with the lathe turned by hand will easily show the runout. A bore off axis, as long as it's straight, can shoot well but may have a lot of windage compared to the sight line. Of course there could be other reasons for bore line and sight line to be so far out.

Still, I've never seen a bent or warped barrel (bore) shoot any kind of decent group.

[waksupi]

A lathe won't tell you a darn thing about if a barrel is straight. Learn to read the light bars in the barrel, and you will know.

[TNsailorman]

I have seen a barrel or two that were bent slightly that were straightened by the the light and press method, "overhead press", that were accurate when done properly by a smith who knew what he was doing. One of them I owned personally, a model 98 (byf) that was bent slightly and shot low because of it. After straightening, it shot to point of aim with 150 grain .323 Hornadys and was quite accurate. If they are bent badly, they do tend to walk the groups when shot enough to get hot. One that a friend had was a .270 Winchester Remington 700 that came from the factory with a slightly bent barrel that was shooting about 12" right at 100 yards. After being straightened by the same gunsmith who strightened mine, it would shoot to point of aim for the first 3 or 4 shots and then start slowly walking back to the right. But let the barrel cool and it shot to point of aim again. Since it was a hunting rifle, it was fine that way but if it was intended to be a varmint rifle for shooting in a dogtown--I'd have recommended him to sell it. My experience anyway, James

[405]

A lathe won't tell you a darn thing about if a barrel is straight. Learn to read the light bars in the barrel, and you will know.

Beg to differ. First things first- there is a difference between bore and barrel. If you center to center a barrel on a lathe and spin it with no run out and/or no wobble then IT IS STRAIGHT by definition! If you center to center it and spin it and you get runout or wobble in the mid section it is bent or warped. If that runout can be measured at either end then it is for certain bored or turned off axis by definition. But, unfortunately as with a lot of this stuff the short "I have a secret" answer while clever and coy helps very little.

[waksupi]

Beg to differ. First things first- there is a difference between bore and barrel. If you center to center a barrel on a lathe and spin it with no run out and/or no wobble then IT IS STRAIGHT by definition! If you center to center it and spin it and you get runout or wobble in the mid section it is bent or warped. If that runout can be measured at either end then it is for certain bored or turned off axis by definition. But, unfortunately as with a lot of this stuff the short "I have a secret" answer while clever and coy helps very little.

Nothing coy about that. If the rings are not concentric in the bore, it is not straight, regardless of how straight the outside of the barrel is. That is where Elmer Keith got called on condemning barrels at the arsenal. Most people don't know what they are looking for, when they look through a barrel. I can look through a barrel, tell you if it is straight or not, and if not, where it is going to shoot to.

[3006guns]

Beg to differ. First things first- there is a difference between bore and barrel. If you center to center a barrel on a lathe and spin it with no run out and/or no wobble then IT IS STRAIGHT by definition! If you center to center it and spin it and you get runout or wobble in the mid section it is bent or warped. If that runout can be measured at either end then it is for certain bored or turned off axis by definition. But, unfortunately as with a lot of this stuff the short "I have a secret" answer while clever and coy helps very little.

To add to the general hilarity......I've put a number of good shooting military barrels between centers in my lathe and found them to be "crooked". That is, the bore was not concentric with the O.D. so my indicator showed several thousandths deviation. Looking through the bore showed a straight hole though. Had I tried to straighen it I would have ruined what accuracy it had.

Deep hole drilling is quite an accomplishment, but sometimes it's necessary to get the finished product out the arsenal door rather than make it perfect!

The O.P. needs to sight through that barrel at a light source and judge if it's bent. Straightening can be done but that doesn't relieve the stress...just puts it in a different spot which can cause "walking" as it heats up. Still, cheaper to straighten it than buying a new barrel!

[Gtek]

A visit to Springfield Armory (THE REAL ONE) with the GCA , they had a light box that the barrel was placed in for internal visual inspection using the light ring method and then pressed straight. I am sure this was only done by the very few that had the gift. there are also rods that can be used. Run out and bend should be checked as far as initial what the ---- is going on. If everything looked good and you had access to chamber reamer, index barrel and cut shoulder and face to rotate your 4 o'clock to 12 o'clock. You said project, right? Gtek

[scb]

http://i487.photobucket.com/albums/rr236/scb2008/bb.jpg
http://i487.photobucket.com/albums/rr236/scb2008/bb1.jpg
Between centers the outside of this barrel has zero run out. Would you call this barrel straight????

[leadman]

I had a Universal carbine that grouped well, but like OP shot so far off to the side the sights were useless.
I took it out of the stock at the range, placed the muzzle on the concrete at an angle, held the receiver in my hand, and stepped on the middle of the barrel. Took several attempts but got it lined up so the sights were almost centered.
I did let the range safety officer, whom I knew, know what I was going to do first.

[303Guy]

That barrel in the illustration scb has shown is no exaggeration. I've fitted a suppressor to one that looked like that. Actually, it looked like that before it was straightened so the OD was all wobbly. After cleaning up the muzzle end OD there was not enough metal for the threads so I fitted a collar and threaded that. It was a skinny barrel to start with.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-148F.jpg

[Kraschenbirn]

Hey, Guys...

Thanks for all the inputs. I pulled the barreled action out of the stock today, clamped it into a set of V-blocks, and bore-sighted it against a target tacked to a tree outside the window of my workshop (approx. 25 yds). Sight settings were unchanged from last range session (cranked all the way to the left) and, with the target centered in the bore, lined up almost perfectly with center of the black. And, reading the 'circles of light' with the ol' MK1 eyeball, the bore, itself, appears straight, too. Without actually pulling the barrel, I've about concluded that (a) the bore, itself, is skewed in relation to the O.D. of the barrel or (b) the receiver threads aren't concentric with the axis of the receiver (thereby 'cocking' the barrel slightly when the barrel shank is screwed tight against the face of the receiver). Guess my next move will be to take it over to my buddy's tool & die shop and get his opinion.

Bill

[303Guy]

How is the bedding? That could conceivably cause it to shoot to one side (and open up the groups too but not necessarily). Just a thought.

[Jeff Michel]

See if you can track down a copy of James Howe's book of Gunsmithing. I think you can download it at the CastbulletPic websight. It goes into a lot of detail of how to straighten a barrel. If you want to see what a barrel press looks like, you can see one similar to the one I made on Brownell's web sight. It's for shotguns but it's plenty strong enough for a rifle barrel. Most barrels have to be straightened following contouring or rifling due to stresses in the barrel steel. Most of the time the bore is not concentric with the outside of the barrel. With very little practice, you will be able to identify a bend, mark it and straighten it. Most military barrels are similarly affected after the steps are removed to make them look a bit more attractive during sporterization.

[303Guy]

See if you can track down a copy of James Howe's book of Gunsmithing.I just happen to to have both volumes! My Uncle gave them to me. He was a gunsmith in the old Rhodesia.

[Gtek]

Is the rear sight base still on? Did you V off rec ring? If there is sight base V just fwd of that on barrel OD. Gtek

[Jeff Michel]

I just happen to to have both volumes! My Uncle gave them to me. He was a gunsmith in the old Rhodesia.

If you learn everything in those volumes, if your not a gunsmith when you start, you will be when you finish. I've used them a resource for 30 years. Your Uncle gave you quite a gift.

[Kraschenbirn]

How is the bedding? That could conceivably cause it to shoot to one side (and open up the groups too but not necessarily). Just a thought.

Receiver is fully glass-bedded and barrel free-floated...sometime before I got the rifle, 'bubba' tried his hand at restocking (one of those 'one-size-fits-all, pre-inletted numbers) and managed to crack the new stock through the recoil lug recess in the process. I recut the recess, installed a brass through-bolt (similar to the original military stock), and glassed from the receiver ring back.


Gtek; Is the rear sight base still on? Did you V off rec ring? If there is sight base V just fwd of that on barrel OD.

Nope, was already gone when I got it...I think 'bubba may have used a cold chisel 'cause it took some serious draw filing to clean up the scrapes and dings. Only used the V-blocks to hold the barreled action for bore-sighting and doing the 'light-ring' check...didn't bother trying to measure either exterior or interior run-out cause my machinist buddy has much better equipment (and skills) for those measurements.

Don't have Howe's books but do have a couple of McFarland's, several volumes of Brownell's "Gunsmith Kinks", and a small collection of armorer's manuals. Haven't yet delved into any of them, though.

Bill

[303Guy]

To get a clearer view of the bore reflected ring, try looking through a primerless case in the chamber. A bend close to the muzzle or breach is hard to see.

Those books sure do have a lot of stuff in them and I am very appreciative of them. They're all I have of my Uncle.

[justashooter]

A lathe won't tell you a darn thing about if a barrel is straight. Learn to read the light bars in the barrel, and you will know.

then learn how to whack a barrel with a rawhide mallet, and you're in like flint.

[KCSO]

If you haven't been taught or learned to read a barrel you probably won't be able to tell straight unless it is real bad. A bent barrel can be straightend but not by just anyone.

[lcclower]

then learn how to whack a barrel with a rawhide mallet, and you're in like flint.
Or whack a shotgun barrel on a bag of shot (moving the pattern higher, as in fine tuning a trap gun).
Nothing has really advanced beyond basic oilfield technology, that is, if it doesn't fit, hit it with a bigger hammer.

[Kraschenbirn]

Took the barreled action by my buddy's tool & die shop yesterday afternoon. In addition to tool & die development, he also does some (very!) high precision prototyping for two or three major players in aerospace and construction technology so he's got some really sophisticated measurement equipment.

To make a long story short, the barrel, itself, ain't bent...actually it's pretty darn straight for a 70 year-old milsurp manufactured in a Nazi-occupied country...like less than .005" radial variance from the hypothetical centerline of the bore. However, as I speculated earlier, the barrel is definitely misaligned with the receiver. Without removing the barrel, we weren't able to determine whether it's a poor threading job on the barrel shank or the receiver ring is bored/threaded off-center . In either case, judging from proof marks and s/n's, it most likely left the factory that way.

Hey, with a barrel-mounted rear sight and full military wood, who'd notice a two or three millimeters misalignment - at the muzzle - on a 540mm long barrel? And, judging from some the off-center groups I've shot, with the original military sights, it was potentially as accurate as any other rifle coming off that same production line.

Haven't yet decided whether or not to try rebarreling...50/50 chance that the receiver threads are out of whack and would show same problem with any barrel I screwed in there. May try a bit of that ol' 'oil field technology' using a pair of v-blocks and a hydraulic press. Center up the receiver sight and 'realign' the barrel to match.

Bill

[KCSO]

I have actually straightend a trade gun barrel at rendevous by using the crotch of an oak tree but that is NOT my prefered method. I have a lead hammer and a set of blocks but usually use a press and v blocks.

[ilcop22]

Bbl mounted irons or a fine optic should turn that into a respectable shooter. It has no collector's value, so I think you'd be better off not messing around with any adjustments to the receiver. That may end up just making things worse. Alternatively, since you know where it groups, good ol' Kentucky windage works, too. ;) Just my 2 cents.

[scb]

If it were mine and I was going to shoot it I'd mount a score using Leupold style base with the windage adjustment on the rear ring. A barrel has to be bent (or misaligned with the receiver) really bad if you can't sight it in with that set-up.

[Kraschenbirn]

If it were mine and I was going to shoot it I'd mount a score using Leupold style base with the windage adjustment on the rear ring.

For a few minutes, last night, I considered installing another military rear sight sleeve...I've got a couple laying around someplace...and using that to mount a base for an IER 'scout-style' scope and then decided against it. The Lyman 48M receiver sight and Williams hooded ramp are already installed, and the stock is a 'classic' low-comb style unsuitable for use with a scope. (Not to mention the considerable 'sweat equity' I've already invested in repairing, rebedding, and refinishing to undo 'Bubba's' butchery.) The way I see things, hangin' a scope on it as a compromise fix is just a shortcut back to somewhere around "Square 1 1/2".

Besides, I don't really care for shooting scoped rifles for fun...competition or varmit hunting, certainly, but for straight recreation, I'll take irons, anytime. If you were to browse through my gun safes, you'd find exactly four pieces - out of over two dozen CF rifles - wearing scopes; all the rest are either milsurps with original military sights or have been fitted with good quality aperature sights.

Bill

[TNsailorman]

I just thought of something, Have you checked the front sight to see if it fitted straight vertically to the bore? I read a piece by a former slave laborer who worked in a rifle factory in Germany during the war and he talked about "sabotage" by doing things like putting front sights on that were slightly off center so that they looked okay to inspectors but would shoot right or left in the field. I believe he mentioned that they would rap the top of the sight with a small hammer to distort it to one side or the other. Probably not the case for you but worth a look. The top of the sight will be bent to the left or right of center if it is the case. He also talked about the sabotage of tanks by leaving bolts in bogey wheels slightly loose so they failed in the field and other things like that. They were careful not to do things which could be traced back to the manufactureing steps; which would bring on retalliation from the Germans. James

[Kraschenbirn]

...just thought of something, Have you checked the front sight to see if it fitted straight vertically to the bore?... James

Original front sight was gone when I got the gun. Bubba had already used a dull hacksaw blade to cut the barrel back to 22" and refaced the muzzle with a wood rasp(?), before cutting a new crown with a pipe reamer(?). One of the first things I did was remove another 1/2", recrown the muzzle, and install a low profile Williams ramp.

Bill

[Hang Fire]

Do like the old timers did. Put the barrel in a good set up of V-blocks so a arbor press can be used. In a darkened room, from outside one end (receiver) shine a light down the bore, place a piece of plain paper several inches from the opposite end of barrel. If the light on the paper does not appear as a near perfect circle, the barrel is bent.

If so, with light still shinning down bore, rotate the barrel until high side is up, then use arbor press to straighten until light shines a true circle on paper.

I have straightened couple ML barrels this way.

[Multigunner]

I've read in multiple sources of sabotage of mausers built in occupied countries during WW2.
They had to be very crafty, since if caught the least they could expect was savage torture and public hanging with a wire noose inserted in the mouth so as to make the dying last as long as possible.

The sabotaged rifles would pass visual examination, and the minimum accuracy requirement, but at anything beyond 200 yards no amount of sight adjustment could keep POI anywhere near a mansized target.
How they managed this is a secret that probably died along with the workmen.