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Bending a barrel ?

Discussion in 'Uncategorized Threads' started by OhioBob, Jul 29, 2007.

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  1. OhioBob

    OhioBob TS Member

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    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
     
  2. Dennisw

    Dennisw Member

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    Dont worry about the math, bend it a little then text fire it.. keep bending til you get it where you want it, I shoot an 1100 and have bent a few barrels
     
  3. buzzgun

    buzzgun Member

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    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. hoggy

    hoggy TS Member

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    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.
     
  5. Duck

    Duck Member

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    Bob,

    Downward?, so it shoot's to high?.
     
  6. hoggy

    hoggy TS Member

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    I think he meant up not down.
     
  7. goose2

    goose2 Well-Known Member

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    How about having Keen sights build you an add on rib that will shoot what ever you tell them you want.
     
  8. OhioBob

    OhioBob TS Member

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    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. Quack Shot

    Quack Shot Active Member

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    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. phirel

    phirel TS Member

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    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
     
  11. XTFreak

    XTFreak TS Member

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    Have you tried a smaller front bead yet? You are not trying to rais the POI that much .. I bet a smaller bead would do the trick.

    Bending the barrel is the fast way to trash the gun. The barrel will resume its orginal shape shortly after bending it.
     
  12. ksaul1

    ksaul1 TS Member

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    Does anyone else hear banjo music?
     
  13. jabrlin

    jabrlin TS Member

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    Bob, A BT 99 has a floating rib, I have bent & striaghtened several barrels on Bt 99s never kinked a rib!Go slow &check often, you have too go a little
    past or it will spring back to what it was before you started! jabrlind
     
  14. ksaul1

    ksaul1 TS Member

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    Does anyone else hear banjo music?
     
  15. phirel

    phirel TS Member

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    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. CharlesR1100

    CharlesR1100 TS Member

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    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.
     
  17. old tex

    old tex TS Member

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    Larry Gravestock shot Rem. 31 and was indeed extremely fast as was his protege a kid named Britt Robinson.
     
  18. goose2

    goose2 Well-Known Member

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    Good heck, if you need to bend a barrel just use it as a jack handle. That should put a kink in it for you. He! He! He!
     
  19. fssberson

    fssberson Active Member

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    Car bumpers work real well.
     
  20. Neil Winston

    Neil Winston Well-Known Member

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    Ohiobob, do you know what "reading the rings" is all about? If not, ask around about it before you go bending. It's the way to do the job you are contemplating.

    Neil
     
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