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Bending a barrel ?

7K views 52 replies 31 participants last post by  AJ100 
#1 ·
Thinking about attempting to bend a BT-99 barrel...would appreciate some input on my math.

I would like to raise the POI @ 13 yards (39 feet) about 4 inches to match up with an another gun I have been shooting.

On a 34 inch barrel if I am able to bend it at the midpoint (17 inches from muzzle) my math skills tell me that I need to bend it about .145 inches downward.

I got this by dividing 39 feet (468 inches) by 17 inches....result was 27.52....divide this into 4 inches equals = .145 inches needed for barrel deflection.

Does this seem reasonable? It seems tiny to me, hence my asking for the math review.

Also, would bending a BT barrel this much cause the rib to buckle?

Welcome your comments. Thanks in advance.

Bob
 
#3 ·
The hard part is not calculating how much deflection is "theoretically" needed...

...it's "surgically" getting that amount of actual bend. The barrel steel has memory, and will keep springing back to the same point of impact until you exceed its yield stress...and you'll have to deflect that barrel a lot more than a tenth of an inch at the bend point, to get her to "stay" bent after you take the load off.

Honestly, this is not a calculation job...it's a trial-and-error job. Trust the paper more than any instrument or calculation (even if you have access to a lathe indicator and are capable of making the measurement).

I would say there is a fair chance of leaving a buckle in the rib, at that magnitude of _upward_ bend (downward would not be as noticeable). But hey, "pretty is as pretty does."
 
#4 ·
You need to bend your barrel about .488 degrees. You didn't tell me the barrel length. 4" rise in 39' is .489degrees. Simple trig. Or if you prefer if you have a 32" barrel and bend it at the 1/2 way point you need to bend it .13675" to make it rise 4" @39'. Of course this is NOT figuring in the natural rise of the shot as it leaves the barrle but I would think it close enough. Hope this helps.
 
#8 ·
Hoggy....as I stated, it's a 34 inch barrel...your calculations seem to indicate that I'm on the right track with my mathmatics.

Duck....I think I need to bend the midpoint of the barrel down to make it shoot higher.

Piddie....as I said, I'm trying to match the POI to another existing gun (BT-99), I'm quite happy with this one and have no desire for an adjustable rib.

Buzzgun....I have a hydraulic press and a dial indicator, thought I might use a hard wooden pressure caul to support the rib during the bending process.

I'm thinking (guessing) it may take upwards of 3x the deflection to get it to stay put when relaxed. I wish I could loosen the rib easily.
 
#9 ·
A keensight rib, an adjustable rib, or stock modifications and adjustment would be much prefered to bending a barrel that is straight. I would NEVER bend a straight barrel to adjust the point of impact. I would only consider doing so if the barrel were not straight and I was going to correct it back to true. Bending a barrel is the ruination of a perfectly good gun.
 
#10 ·
Barrel bending was rather common form about 1955 to 1975. This was before we had adjustable ribs and combs. It does work. I believe the best tools to bend a barrel is a padded piece of steel (re-bar works) about 5 feet long and the rear bumper of a pick up truck. The barrel should be bent just a little at several points to protect the rib. Most important is bending the barrel a little and then testing the POI.

A second method of successfully bending a barrel is to support the ends of the barrel between sand bags on the bed of a pick up and with great care, applying pressure to the mid section of the barrel with the spare tire.

Larry Gravestock preferred the pick up bumper method over the spare tire method. With all bending, it is critical to bend a little and then test the gun. Larry taught me how to both bend barrels and pay close attention to my income tax returns. He was an outstanding shooter. It is too bad he had to leave so quickly.

Pat Ireland
 
#15 ·
I hear banjo music frequently. In many areas it is known as Bluegrass but in the Blue Ridge Mountains where I live, it is known as Mountain Music. I like the music and I like to flat foot. When driving locally, the radio station I listen to will play a wonderful Strauss Waltz followed by Crooked Creek. I feel sorry for people who associate the backwoods from backwards.

Pat Ireland
 
#16 ·
Brownell's sells a device to straighten a bent barrel. Ought to work putting the bend in also.

I think you want to re-curve the barrel, more than bend it, however.

Old-timers like to tell stories of guys using the fork of a good, stout tree next to the barn for the same thing. Stick your johnson bar in the breach end and tug. They also said...

"Ribs? Beads? Who needs 'em? Birds don't know!" That sort of crap.

Good luck.
 
#21 ·
jabrlind....thanks for the info on the floating rib.

Neil....I believe I know what you are referring to when you say "reading the rings", I look through the barrels of many of my guns and can tell which and how many of them are bent from the factory.

My Super X-1 "trap" barrels happen to have a considerable bend right from Winchester. They look somewhat like the venue for the 70 meter ski jumping at the winter Olympics.

A lot of the respondents so far have indicated that bending a barrel is something akin to inbreeding. Hey guys...I'm only talking about bending a barrel in a controlled hydraulic press...I don't need a car bumper, tree fork or bumper jack.

Of course I could do something really cool, like get out my Milwaukee Magnum Hole Shooter and drill some teeny little holes in the barrel, or get my Ridgid pipe reamers and take some of that unnecessary extra metal out of the forcing cones, maybe my Sawzall and some threaded rod for one of those custom adjustable comb jobs.

Regardless, thanks for all your input....I take it all in with due consideration.

Bob
 
#22 ·
Good shooter I know from Delaware, Bob Higgins, has a tricked out 1100 with a "banana" barrel as we called it.

It shoots 130% high and it has got to be the one of the weirder thing I have seen in a while.

I he was not one of the best shooters/teachers out there I would have scratched my head when I saw it.
 
#23 ·
OhioBob, it's nice you have a press, but you have gotten the wrong idea about bending from these guys. It's how factories make guns shoot straight, all of them. The gun you now shoot was probably bent and Beretta 303's all shot left and had to be bent to the right to work.


This is as good a way as any:






It works and to put $$$ into a comb when this works so well and can be undone makes no sense. Just bend it.

Neil
 
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