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What's involved in fitting barrel to shotgun?

Discussion in 'Shooting Related Threads' started by dimapower, Feb 4, 2010.

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  1. dimapower

    dimapower Member

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    What

    I have a Perazzi MX2000 unsingle. Found a nice MX8 O/U barrel to complete my combo gun. The MX8 barrel doesn't fit perfectly: 1) closing the action requires a little more force than my unsingle barrel, 2) the lever is closer to center with the O/U, and 3) the forearm is slightly loose on the side closest to the muzzle.

    Are any of these issues problematic or are they minor?

    Jon
     
  2. jimrich60

    jimrich60 Member

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    In and of themselves, they may seem minor. But they may also be indicators of improper headspacing, locking bolts not fitting and locking up solidly (potentially disastrous), trunnions not fitting smoothly and properly (could accelerate wear on receiver, and thus cause problems eventually with original barrel, and other issues. Barrels should be fitted by a knowledgeable and skilled gunsmith to avoid problems and ensure safe operation. Anything else may be risking serious damage and/or harm to the shooter and/or others.

    Jim R
     
  3. loop02

    loop02 Member

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    You probably should contact Dan at Giacamo sports. There are several issues in fitting two barrels with unequal lug wear to the same forend. On a Perrazi the correct way, in my opinion is to have the loosest barrel lugs welded up and machined to match. But then, with unequal usage, one barrel will wear more than the other, over time, causing one to be better fit than then other. If you change locks, one will fit better than the other, unless they are fit again. They will never stay the same.
     
  4. Setterman

    Setterman Well-Known Member

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    Sounds like you do not have a good fit. I would send it to Giacomo, Laurence Palinski, or one of the other P-gun mechanics just to be safe.
     
  5. Anchorsteam

    Anchorsteam TS Member

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    About 80 bucks to the good folks at Ottsville and the barrel fits perfect.
     
  6. Steve W

    Steve W Well-Known Member

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    Jon, seems you need professional fitting. Here're the possible reasons for your situation as you stated.

    1) The forend might be grinding your receiver with the new barrel on it, the under lug has less wear than your unsingle.

    2) The new barrel has lower shoulder lugs than your unsingle.

    3) Your unsingle barrel is thicker than the O/U.

    Besides your observations, the head space might not be right, ejector timing could be off. These are all the good reasons to have a competent gunsmith check it out.
     
  7. dimapower

    dimapower Member

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    Thanks for all of the advice.

    I'm currently reviewing this barrel and want to pattern it before I commit to buying. In it's current, not a perfect fit condition, do you all think it would be okay to shoot a few pattern shots? Assuming it patterns well, I would go ahead and buy it, then send it off to be fitted.
     
  8. Steve W

    Steve W Well-Known Member

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    Not a good idea. The risk is too high.

    Head space is critical to safety in this case. I wouldn't fire it before I'm sure. Check the following (but not limit to):

    If you can see ANY light between the breech face and chamber, top rib sticking up even by 1/32" inch from the top of receiver, DON'T fire it.
     
  9. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    Does the owner have the original receiver so that you might see how the barrels shoot? Or another MX-8?? If not, I'd send it Giacomos for fitting before I shot it. Hap
     
  10. loop02

    loop02 Member

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    If the chokes have not been fooled with and you want the barrels, get them fitted, and then have Jimmy Eyster tweak the chokes for you if you don't like it.
     
  11. TOOLMAKER 251

    TOOLMAKER 251 Active Member

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    Your breach is open over .006 if you can get 3 strips of paper between the faces, you also have a half ass bolt lockup. When it's fitted right you should not even be able to get 1 strip of paper in the recoil face.
     
  12. dimapower

    dimapower Member

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    Not sure if I explained it properly, but there is no way I can slide even 1 sheet of paper between the faces. However, I can cut a little circle the size of a 12 gauge round, place it on top of the round and close the action.
     
  13. TOOLMAKER 251

    TOOLMAKER 251 Active Member

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    See how much paper you can put between the top part of the receiver and the monobloc when it is already closed. From your picture it looks like there is a small gap in the joint, but what I am seeing might also be the engraved line that Perazzi puts around the boarder of the recoil face.
     
  14. dimapower

    dimapower Member

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    I can't slide 1 piece of paper when closed.
     
  15. MOP

    MOP Active Member

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    Based on my experience and the photographs of your lock-up, it won't hurt a thing to fire some patterning shots.
     
  16. Setterman

    Setterman Well-Known Member

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    Laurence Palinski. I'll PM his cell number to you. Have him look at your pictures on the site and describe to him the clearances you have. He'll tell you for sure.

    Rosey
     
  17. romie

    romie Active Member

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    Dougs gunshop.He is quick fair.I had him fit one this fall
    Monty
     
  18. Anchorsteam

    Anchorsteam TS Member

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    The gunsmith might have to make an adjustment to the cocking rods or equivalent function in a P-gun.
     
  19. Anchorsteam

    Anchorsteam TS Member

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    The gunsmith might have to make an adjustment to the cocking rods or equivalent function in a P-gun.
     
  20. GunDr

    GunDr Well-Known Member

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    Headspacing on a shotgun is a little more forgiving than on a rifle, but it does have it's limit.

    Headspacing a break-open shotgun should involve the use of a "NO-GO" & "GO" headspace guage. Once the chamber is cut to a predetermined depth, the use of a rim-cutter then is use to do the final .010"-.015" to allow the "GO" guage to sit flush with the breech end of the bbl.

    Making any adjustments to the headspacing first requires that the bbl is fitted properly to the receiver, and by properly fitted, I mean that the two breech faces, that of the bbl and that of the receiver, must be as close to 100% contact with each other.

    Note...The headspace guages that anyone can purchase are fine for checking pumps and autos, but for break-open guns, the "head" of the guage must be modified to allow the bbl to swing closed properly.

    Having a small gap in the standing breech does not necessarily mean you have excessive headspace. As long as the GO guage is flush, there could possibly up to .006" of gap and headspace safely. The problem with a gap is that it will forever get greater with the more rounds you put through the gun, as the hooks on the bbl and the joint roll pins/trunnions wear. Those guns with bifurcated lugs will minimize the forward movement of the bbls, but eventually you will feel the mono-block begin to bump into the lugs in the receiver as the gun closes.

    Having approx .003"-.005" of gap in the water-table near the breech face and a tight breech face, a gun would last hundreds of thousands of rounds.

    For a long time in order to correct a gappy breech face on a Perazzi involved replacing the joint roll pins. This is a very pricey repair...upwards of $800 or more, especially more if the gun has been plated or engraved.

    Now, forgive me for a little self-promotion....

    This year I've started welding the hooks on the bbls. I spent a couple of days making fixtures to allow me to grab dimensions from the mono-block, and fixtures for re-machining the hooks. I've done 5 bbls since this last summer, and they came out great. Once I've determined the amount of gap, and a few thoudandths more for final timing and fitting, the breech faces are tight and approx .003" at the water table for a forever tight breech face.

    If you're worried about the heat being applied to the chamber area...this area is protected by flooding the bores. The welding rod is of a tool steel to maximize the life of the hook area. It does remain soft enough to cut with a file.

    Doug
     
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