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Back bored vs. over bored barrel

geeguy
On another thread Trap55 brought up an interesting question. I was under the assumption the a shotgun "back-bored" barrel was made to reduce the ID by about .070" to lighten the barrel but did not effect the choke area, and "over-bored" was opening the entire dia. of the barrel which did effect the choke area.

I do find many "back-bored" shotguns use the same tubes as the Std. barrel. (not ref. to length of forcing cones in this question)

Are the terms used one and the same?

Enlighten me.
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Comments

7 comments

Date Votes
  • perry shooter
    I always though that one could take a cylinder cut off barrel and Back Bore it this would increase the diameter of the bore between the chamber end and the muzzel end up to about 4 inches from the muzzel which would then cause the shot string to contract and actually cause the pattern to shoot tighter .I thought that back bore would make any barrel shoot tighter groups and mainly used for Handicap distance at TRAP shooting
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  • TRAP55
    geeguy, you were referring to true "back bored" barrels, and I was referring to "over bored" barrels. You were correct, and I missed it.[:I]
    The confusion lies with the manufactures that have labeled their over bored barrels, as back bored, and that has been adopted as industry standard now.
    There seems to be a divide in opinion about any advantage to "over bored" barrels. I'm in the camp that says it does. There is less felt recoil, less shot deformation, and a shorter shot string.
    I have two Browning Upland O/U's that are pretty much identical, except one has fixed choke barrels, and the other has the INV+ barrels. Same choke "designation", same ammo, on a pattern board and the difference is obvious.
    This is Browning's choke size chart, note the choke ID for Fixed, INV, and INV+.

    BrowningChokeSizes-1.jpg
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  • geeguy
    Trap55 - I always read your posts with great interest and due respect, so I thought my assumptions were incorrect after your post and I just wanted to make sure of my thoughts.

    I did look this up a little after our posts and it appears that (as you said) everyone seems to interchange the terms now days.

    Always good to learn something from this group. Thanks.
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  • Maalox
    I thought "Back Bored" was used to true up any manufacturing inconsistencies in the barrel inside diameter. I had Briley work on a Beretta 391 a number of years ago. They had a package which back bored the barrel, lengthened the forcing cone, ported the barrel and included a trigger job. This package also included new extended choke tubes. I was very happy with the work and the gun is still a sweet shooter.
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  • duckhunter
    Back in the "good ol days", late 50's, we used a term "JUG CHOKED" in which a barrel was over bored about 3 inches from the muzzel to make a tighter choke.
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  • TRAP55
    quote:Originally posted by Maalox
    I thought "Back Bored" was used to true up any manufacturing inconsistencies in the barrel inside diameter. I had Briley work on a Beretta 391 a number of years ago. They had a package which back bored the barrel, lengthened the forcing cone, ported the barrel and included a trigger job. This package also included new extended choke tubes. I was very happy with the work and the gun is still a sweet shooter.
    Maalox, What Briley did was over exaggerate the forcing cone when it was lengthened, all the way out to the choke. They can do that on a barrel like yours that has a thick enough barrel wall. Lengthening the forcing cone is the best money you can spend on a shotgun.

    Jess Briley and my BIL are shooting buds. Years back he did a barrel for my BIL's S&W 1000 auto loader. He eventually wore the gun out, and gave me the barrel with extended tubes for my S&W. I have a safe full of shotguns, and with the exception of a Fausti DEA SxS, there isn't one of them that shoots as well that gun does with that barrel.

    I'm curious as to what Rosie finds out about that Rem barrel, I was unaware that Rem had a barrel like that. I'd like to know if they overbored the barrel, or worked it like briley does.

    duckhunter, jug chokes...that goes back aways. Saw a few of those that bulged or split. Looked like a turkey choked barrel that someone had shot one too many slugs through.[:)] It's interesting to see what all the trial and error has resulted in factory barrels today.
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  • sprint
    TRAP55,

    "The confusion lies with the manufactures that have labeled their over bored barrels, as back bored, and that has been adopted as industry standard now."

    It is my understanding that the "industry standard" for choke designation is as published in the SAAMI glossary.

    Here is the link to the SAAMI site. http://www.saami.org/Glossary/index.cfm

    Sprint
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