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Back boring a Perazzi barrel

Discussion in 'Gunsmithing' started by LeoTunes, Feb 14, 2017.

  1. LeoTunes

    LeoTunes Member

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    I would like to ask the knowledgeable members of this prestiged forum about what to do to reduce the weight of my shotgun. My barrel is 18.7mm (.736"), 32 inches and weight 1,7kg (3.75 pounds). I want to reduce about 4 to 5 ounces of its weight ( to 3.4 p0unds). Using a back bore formula that I found online I would have to take about 0.003" of each barrel, so my barrel should become 18.8 (.738"). I plan to send the barrel to Briley.
    Is there someone that already did that? Is it something that is safe to do? Will the back bore process remove the internal chrome of my barrel? I appreciate any comment or advise. Thank you.
     
  2. Don Rackley

    Don Rackley Well-Known Member Supporting Vendor

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    Leo,

    How does the barrel pattern?

    If the barrel patterns very well, why not put about 4-6 ounces of weight in the buttstock? You will get less recoil and the balance of the gun will be about the same as if you backbored the barrel. You will not spend as much money as if you had backbored the barrel and if you know the barrel patterns well, you are not fixing anything other than balance and swing dynamics.

    Just my opinion,

    Don Rackley
     
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  3. JACK

    JACK Well-Known Member Supporting Vendor

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    I think your formula is off. A few thou from the bbl willnot get you to 3.75 ounces of metla reduction. Paste/post the formula you found for us to view. Please.
     
  4. LeoTunes

    LeoTunes Member

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    Here is the formula that I found and used.

    weight change in ounces = 7.14 x IDB x (IDA-IDB) x L x N

    IDB = barrel inner diameter before backboring, in inches
    IDA = barrel inner diameter after backboring, in inches
    L = length of backbored area in inches (e.g., barrel length minus chamber and choke)
    N = number of barrels


    For the barrel I used 25" of back boring (32" - chamber and choke).

    The total reduction that I got through the formula after back boring was about 4 ounces or 0.35 pounds (3.75 - 3.4 pounds).
     
    Last edited: Feb 15, 2017
  5. LeoTunes

    LeoTunes Member

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    Don,
    Thank you for your reply and advise. I already did that and the gun is balanced and shooting well, but I end up with the gun weighting more than 9 pounds. I want to reduce the overall weight to about 8.5 pounds. If I take 4 or 5 ounces from the barrel I can take 4 or 5 ounces from the stock and reduce the overall weight about 10 to 12 ounces to achieve a 0.5 pounds weigh reduction. Am I over thinking this or looking for a insignificant modification?
     
  6. Jim Pettengill

    Jim Pettengill TS Member

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    I think you will find that back boring the barrels will cause the soft soldered ribs to come loose much faster after it is bored out. The thinner barrels cause the temperature to rise and cause premature failure of the solder joints. I bought an MX-8 that Wilkinson overbored, I liked the way it performed but did not like re-soldering the ribs back on every year or two. I finally usd a lead free solder, which has a slightly higher melt point and the ribs have lasted about 4 years, so far. JimPettengill
     
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  7. LeoTunes

    LeoTunes Member

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    Jim,

    Thank you for sharing your experience. I read that in another post and it is a concern. I don't know yet if I will do it or not. I am gathering information and advises of more experience shooters as you to decide.

    Leo
     
  8. Stl Flyn

    Stl Flyn Banned User Banned

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    I think you would be surprised also, at how much a barrel actually flexes when shot is traveling through it. Removing more metal I would think can cause even more deflection, which puts pressure on those solder joints.
     
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  9. flashmax

    flashmax Well-Known Member

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    Your last question first. Yes backboring will remove the chrome lining of your bbl. But last I heard Perazzi wasn't chroming the bores, only polishing the bejesus out of them. Chambers are/were chromed but won't be hurt by backboring. I'm not sure you can get where you are trying to go by backboring though.
     
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  10. semperfi909

    semperfi909 Well-Known Member

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    You seem to have great potential with this to not only not achieve what you seek but incur some considerable expense that will very likely not be recoverable.

    Why not consider selling what you have and getting what you want? In the long term the economics alone show that to be a better course.

    JMO of course
     
  11. R&R Rancher

    R&R Rancher Member

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    Go back and check your formula. Area is pi x diameter squared divided by 4. Area of a .738 diameter circle is .4278. Area of a .736 circle is .4254. Difference is .0024 square inches. Multiply that by 25 inches and by .284 pounds per cubic inch and by 2 for the number of barrels and I get .034 pounds or .54 of an ounce.
     
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  12. Stl Flyn

    Stl Flyn Banned User Banned

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    OK, so he would be better off cutting six inches off the barrel.
     
  13. R&R Rancher

    R&R Rancher Member

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    If he wants to reduce his weight by 5 ounces, math says he needs to back bore to .751. Possibly doable, but how much meat would be left in the barrel walls?
     
  14. Don Rackley

    Don Rackley Well-Known Member Supporting Vendor

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    Leo,

    In my opinion, and I haven't seen the way you mount or move the gun or how well you break targets, I think you are chasing a very small change for a target gun.

    If you are strong enough to move the 9 pound gun for a 300 target day, I would leave it alone, it will kick less.
     
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  15. ramorton

    ramorton TS Supporters TS Supporters

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    18.8 is .740

    You'll never notice the difference in weight.
     
  16. Sundown

    Sundown Banned User Banned

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    I wouldn't have my barrel backbored. If it came from the factory, that's one thing. I've seen problems with some that weren't done right.
     
  17. grunt

    grunt Well-Known Member

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    Briley wont do the job if they think the barrel would be unsafe.
     
  18. ChiefR53

    ChiefR53 TS Member

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    There are lots of Perazzi barrels out there. Can you find one of the weight you want?
     
  19. LeoTunes

    LeoTunes Member

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    I want to say a big thank you for all the advises and help that I got from you all. I will leave my barrel alone and shoot it like it is. Probably you guys saved me a bunch of money.
     
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  20. LeoTunes

    LeoTunes Member

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    Regarding the formula, I don't have the knowledge to revise it. I just used what I found. Sorry.