Author Topic: bent barrel (Read 5140 times)

thecapgunkid · « **on:** March 01, 2017, 03:06:59 PM »

How do you tell if a barrel's bent? Any tools or methods that are out there?

Thanks

Capgun

smallpatch · « **Reply #1 on:** March 01, 2017, 05:27:07 PM »

Some good lighting, and a string inside the bore.
Just curious, what are you trying to find?

thecapgunkid · « **Reply #2 on:** March 01, 2017, 06:25:52 PM »

Thanks, Dane.

Nothing in particular as of now, but sooner or later I am going to run into this problem.

The likely candidates are the octagon to round smoothbores I just made, so I need to know how to go about checking

P.W.Berkuta · « **Reply #3 on:** March 01, 2017, 07:36:46 PM »

I think you would have to shoot it first UNLESS the barrel is obviously so severly bent that it can be seen by the naked eye. My thoughts

rich pierce · « **Reply #4 on:** March 01, 2017, 07:44:16 PM »

I once had a barrel with the bore centered at both ends and the muzzle squared off in a lathe but it shot so hard left the rear sight was almost off the barrel. Should have bent it.

Hungry Horse · « **Reply #5 on:** March 01, 2017, 08:34:00 PM »

I had a Mouery squirrel rifle in .45 cal. That had the same problem. I never figured out what was wrong with it. It shot fine with the sight way over on the left side, but just felt weird to shoot like that.

Hungry Horse

EC121 · « **Reply #6 on:** March 02, 2017, 01:01:05 AM »

You can look through the barrel at a straight line and see if the reflection down the bore is straight. I've never done it, but a search will come up with checking procedures. I've also read about using a string stretched down the barrel but don't remember where.

hudson · « **Reply #7 on:** March 02, 2017, 02:51:11 AM »

A thought would be placing the barrel on a flat surface, rotate and watch for clearance between barrel and flat surface. Barrels are sometimes bent during the process of milling the flats. Though this doesn't always mean the bore is crocked it sometimes finds the problem. Last 40 cal. x 42" I had this was found to be the problem. Barrel was straitened by blocking up end and using a large c- clamp on the edge of a good bench. Constant measurements and blocking was required. I haven’t had real good luck looking through the bore and watching the reflection well rotating. A crocked bore or bent barrel shows up quick when being spun in a lathe.

Marcruger · « **Reply #8 on:** March 02, 2017, 05:14:35 AM »

A barrel can get bent. I had an A-weight .50 get bent somewhere in the mailing process. It showed up by the sight needing to be way over to the side to sight in.

Easy to see on a swamped barrel, just measure the relief under the barrel flats at the same point for all 8 sides. Mine showed clearly something was bent.

If you are shooting and the sight is way off, it may not be bent. It may simply be runout that wasn't oriented correctly to the bottom or top when built.

Just some thoughts. Marc

smallpatch · « **Reply #9 on:** March 02, 2017, 05:49:07 PM »

Like Marc said.... the outside can potentially show straight, and the bore can still be off. I have a couple of rifles that I have intentionally bent to POA. Just because the bore is straight, doesn't mean it will shoot to POA, due to run out, and the orientation of that run out.
Shoot it, find a proper ball, patch, load combo, then bend it if necessary.

retired fella · « **Reply #10 on:** March 02, 2017, 08:46:18 PM »

smallpatch,,
would you bend cold or with heat?

Daryl · « **Reply #11 on:** March 03, 2017, 01:46:33 AM »

Quote from: smallpatch on March 02, 2017, 05:49:07 PM

Like Marc said.... the outside can potentially show straight, and the bore can still be off. I have a couple of rifles that I have intentionally bent to POA. Just because the bore is straight, doesn't mean it will shoot to POA, due to run out, and the orientation of that run out.
Shoot it, find a proper ball, patch, load combo, then bend it if necessary.

I had one, don't know what make, perfectly straight on the outside, but the bore must have made a left hand turn close to the muzzle - obviously off centre at the muzzle. The sights had to be drifted, rear to the right as far as possible, with the front sight drifted to the left as far as possible - it looked utterly stupid and felt clumsy, so I pulled off that 42" .50 cal. x7/8" barrel and had Taylor put on a .45GM 7/8" octagonal barrel - perfect. It shot plumb centre with the sights in the middle of the flats.

Marcruger · « **Reply #12 on:** March 03, 2017, 03:23:23 PM »

A good friend explained runout to me early on. The Gunsmith of Grenville County book has a whole section on checking to make sure runout is at the top or bottom before proceeding. I am sure you know all of this Daryl, I am just posting for others who may not.

Measure at the muzzle and breech to make sure you know which (if any) flat has the least distance from the bore to the flat. That flat should be either up or down. Most barrel makers mark their barrels so runout is oriented up or down, and mark the bottom flat. If runout is not at the top or bottom, then the bore is aiming in a different direction than the external part of the barrel with the sights. Not good. The gun will shoot right or left, but the sights will be straight. Not fun.

If runout is oriented up or down, you simply file your sights. No problem.

If you have an unmarked barrel, always check for runout before building.

I hope this helps someone. Best wishes, Marc

smallpatch · « **Reply #13 on:** March 03, 2017, 04:43:07 PM »

Retired fella,
Cold bend. No heat necessary.

You want a gradual bend, not one concentrated where the heat is.

Daryl · « **Reply #14 on:** March 03, 2017, 11:23:17 PM »

Yes - I recall Douglas mentioning this with every barrel bought - along with about all the gun digests and gun making books in the 70's saying the same thing. The rifle with the severe run-out was 'as purchased' and couldn't be changed due to dovetails, etc. It was easier to re-barrel.

When bending the barrel to correct the poi ---IF you KINK the barrel- ie: SHARP bend, I wold replace that barrel immediately, then cut each side of the kink and use it for pistols.

Marcruger · « **Reply #15 on:** March 03, 2017, 11:40:10 PM »

No insult intended Daryl. I'd have had that one re-barreled too. Best wishes Marc

Daryl · « **Reply #16 on:** March 06, 2017, 04:03:00 AM »

NP- no offense taken, Mark.

Hungry Horse · « **Reply #17 on:** March 06, 2017, 08:24:18 PM »

Douglas barrels had instruction that stated that unless the barrel was marked with an X indicating a premium barrel, the Douglas stamping at the breech should be put on the bottom, to orient the runout properly.

Hungry Horse

rich pierce · « **Reply #18 on:** March 06, 2017, 10:44:22 PM »

Runout at the breech and muzzle are largely a thing of the past because the round stock is bored and reamed and rifled then the exterior profile is machined nowadays. It is still possible there's a curve in the bore, I suppose. Hard to figure.

Waksupi · « **Reply #19 on:** March 06, 2017, 11:43:31 PM »

On inspecting barrels

Apparently, there is little knowledge of what you are looking at, when you look through the bore of a firearm.
I learned how to inspect a barrel at the Bauska Rifle Barrel, Co., from Les Bauska.

He told me the way to train your eye, is to first look through a shotgun barrel. You will see concentric circles the length of the barrel.
These are light bars, and there are somewhere around 100,000 per inch.
On any good barrel, you will see these are all the same size for the length of the barrel.

On a crooked barrel, you can see the light bars are oblong in the bad part of the barrel. They will show you which direction
a barrel needs bent to correct things.

This holds true on a rifle barrel, although it is a bit more difficult to read for some. Others never can see it. The bore of the barrel is a polished smooth cylinder.
You can train yourself to see the light bars, even with the rifling. Rough rifling is inconsequential, as long it is not cutting patches. Shoot it smooth, or lap it.

I've been the barrel inspector for three gun companies. I was able to teach some, but they were not common.

So, that gives you an idea of how to see if a barrel is straight. If you can't see and understand what you are seeing, you are
swinging blindfolded if you need to bend the barrel.

Daryl · « **Reply #20 on:** March 07, 2017, 04:43:43 AM »

I spent a day in Les's shop in March 1975, straightening barrels for him, and selecting 10 or so to take back up North, with me. That was a fun day.

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Author Topic: bent barrel (Read 5140 times)