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Thread: Diameters Vary Among Bullets of Same Caliber

  1. #1

    Diameters Vary Among Bullets of Same Caliber

    I came across this interesting article this evening.
    Regards JCS

  2. #2
    That could be interesting to those that like to burn at max. pressure all the time

  3. #3
    I don't think it will have much if any effect at all. If you are a handloader who has worked up loads with a bullet that has slight variances in diameter (in the ten-thousandths of an inch) and done more than fired one group and called it good, then your load has already taken in to account the variances over the average pressures in your string of shots. Bullet diameter is a funny thing. I have a Swedish Mauser target rifle with the characteristic over-sized groove diameter that shoots under MOA with .264" bullets. I have a No1, MKII .303 that has a .310" grove diameter and I shoot .314" heat treated cast bullets through that. My Benny Rifle 218 Bee has a .223" groove diameter and I'm supposed to shoot .223" bullets to avoid "pressure problems", but I shoot .224" bullets with absolutely no problems. Serious cast bullet shooters know the simple truth about rifle barrels. The average factory barrel is seldom nominal groove diameter.~Muir

    PS: There is the possibility that severly undersized bullets at max pressure could cause erosion, but a ten thousandth of and inch will probably obturate at the usual pressures.
    Last edited by Muir; 05-10-2012 at 13:16.

  4. #4
    I'm fairly certain I saw some research somewhere that demonstrated that, within reason, using oversized bullets made little or no difference to pressure. Might be worth getting google on your side and doing some searching if you are worried or interested.
    For self catering accommodation on the Isle of Lewis please visit:

  5. #5
    have a google for a guy that developed tapered barrels!
    now that is amusing. starts of .224 and end up .17 at the muzzle

  6. #6
    Bench rest shooters have been using fatties for years.

    I did once have to spec an oversize free bore on a reamer order to accommodate some 7mm cauterucio bullets that were pretty much a full thou. over diameter. This isn't the kind of thing that would affect factory rifles though. Just work up he load.

  7. #7
    A stalker I know fired a 7x57 cartridge through a 270 Win rifle. The rifle and stalker both survived, though the latter was, er, fairly shaken!

  8. #8
    I once saw what was left of a 7x57 that someone fired a 308 through. It was destroyed. ....As was the shooter's underwear.~Muir

  9. #9
    Quote Originally Posted by jcampbellsmith View Post
    I came across this interesting article this evening.
    Regards JCS

    Truly mental masturbation without reference to metrology standards / environment.

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