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shotgun changes point of impact

Discussion in 'Shooting Related Threads' started by texasbilly, Mar 22, 2010.

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  1. texasbilly

    texasbilly Member

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    I own a light weight, 16 gauge, Dumoulin double barrel shotgun. It is about 65 years old. Though it is a field grade, I have tried to use it for sporting clays.

    This is my problem. It seems that when I start shooting it on the sporting clays field, it shoots "flat". If I point the gun at the target, I can break it. Later as the gun heats up from shooting, the point of impact of the shot seems to drop. Late in the game, I need to completely cover the bird to hit it. Is it possible that the point of impact is dropping due to the heat of the barrels? If so, is there a fix to this problem, or should I limit the use of the gun to hunting?

    texasbilly@comcast.net
     
  2. GW22

    GW22 Active Member

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    Billy:

    Typical barrel heat can not possibly cause enough droop to create a meaningful change in POI. Certainly not enough for any human to perceive from shooting at clays.

    -Gary
     
  3. Barry C. Roach

    Barry C. Roach Well-Known Member

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    It's French so it goes any way it needs to.
     
  4. craby boy

    craby boy TS Member

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    I think gun mount or some other component of your form changes as you get into your round,

    Speaking from experience


    Pete
     
  5. willing

    willing Member

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    It may be my imagination, but I always thought that my SxS changed
    POI when I shot the full barrel continusely,left to right not up and down.

    Bill
     
  6. oskerspap12

    oskerspap12 Active Member

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    I agree with crabby.
     
  7. texasbilly

    texasbilly Member

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    I appreciate your comments. Perhaps I should have told you that the Belgian made shotgun is a light weight, 16 gauge that was built on a 20 gauge frame. Over time I have noticed this shift of impact, and I noticed it only happens after the barrels heat up.

    I contacted a cryogenics business that confirmed that many shotgun do shift under conditions of heat. During manufacture years ago, barrels were bent at the factory to straighten them. Heat makes them return to this natural (bent) shape. Deep freezing the barrels changes the molecular structure of the metal such that they remain in their "new" natural condition (after freezing) even when they get hot.

    I think I will send my barrels for freezing. It can't hurt.

    texasbilly
     
  8. Neil Winston

    Neil Winston Well-Known Member

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    billy, do this first for us, will you? Set up a rest of some sort that you can put your gun on and a sheet of paper to shoot at at 13 or 15 yards, something like that. Draw some crosses on the paper as aimpoints. Shoot three or four shots with plenty of cool-down time. Then shoot a half a dozen shot quick as you can, just in the air will be fine, and repeat shooting at the crosses without delay so as to tell for sure whether the POI has changed or not. If you don't use a rest, don't bother; you won't learn anything and we won't be able to trust your results.

    Then send it out and repeat the test when it comes back. There are lots of shooters who would like the the data from both tests.

    Neil
     
  9. grunt

    grunt TS Supporters TS Supporters

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  10. texasbilly

    texasbilly Member

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    Neil:

    That is my plan. I will pattern the shotgun barrels from a rest at 30 yards. Both barrels are full choke so I should easily see the patterns and points of impact. Then I will shoot about a dozen shells to heat the barrels, and shoot the patterns again. Assuming there is a change in the point of impact as I suspect, I will send the barrels for cryogenic treatment. Upon their return, I will run the tests again.

    I have a lousy memory, but I will try to report the results of the tests on this site. Maybe we can learn something; maybe I will learn that I am not a good shot. We will see.

    texasbilly
     
  11. pheasantmaster

    pheasantmaster Well-Known Member

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    For those that don't think a barrel can walk, I have a question or actually two.

    First, who do you know that has shot doubles proficiently with old style (rem 32 or K32) K80 non Vandalia?

    Who do you know that has shot a stock 90T proficiently?

    Both are trap related subjects.
     
  12. trapshooterjoe7

    trapshooterjoe7 Member

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    Martin, i know 1 guy that shoots a low rib 90-T, he is AA and shoots it really well. Tell us what you mean??? Joe
     
  13. Neil Winston

    Neil Winston Well-Known Member

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    backwoods, for a laid-back country guy with maybe jes' your pappy's old M12, you sure seem to make a lot of good guesses.

    A couple of months ago I posted this on a similar thread on Shotgunworld.

    "It depends on the gun. But I've had at least one which moved from OK to NDG in a few shots. Really.

    John Findorff was my coach at Metro in the the late 80's and we had one of those huge WW International traps to practice "bunker" on; the Minneapolis Gun Club had an NRA event every year and I wanted to be competitive. I'd shoot both shots most of the time and was able to hit something, either the bird or pieces, on many of the shots. At the start, that is. Then, virtually nothing with the second barrel.

    I'd say to John "Hey, you try this! I can't hit zilch all of a sudden. Tell me where _you_ think it is shooting!" He'd finish his cigarette - and maybe one more just for good measure - , and ever-so-slowly make it to the line. I'd pull a couple of targets; he'd break them, and say "I keep telling you, it shoots right where I point it."

    Finally, some serious mis-points with the second barrel- way under and a solid hit - led us to the pattern board at 13 yards, off a rest. Result: Shot one, everything fine. Shot two, same. But by shot five, the POI had moved several inches high and less to the right. In all, clearly enough to change a flat shooter to a high shooter with the resulting change in needed aiming, which no one could do. It had worked for John because his cigarette and so on had given the barrels time to cool and the barrels were back on track by the time he tested it.

    I sold it, but it led me to invent a shop-located way to test for that kind of problem and my conclusion that _all_ move at least a bit; a very few move a lot. Oh yes, as a point of interest, the barrels I've bent are _no_ more likely to move a lot than factory-untouched ones."

    Here's my question, backwoods: How did you know it was an K32 barrel? It was a Vandalia one, though, so you are being docked half a point, from A+ down to A.

    Neil
     
  14. phirel

    phirel TS Member

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    texasbilly- Use the method described by Neil but do not "pattern" the gun at 30 yards. At that distance you will have to guess where the rel center of the pattern is. At 13 yards you can accurately tell where the center is. If your POI is moving an inch or two with barrel heat you have to be abler to measure the POI within an inch. This cannot be done at 30 yards.

    Pat Ireland
     
  15. Fritzboy

    Fritzboy TS Member

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    Are you using 7.5 or8's?
     
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