super tight chamber??

Discussion in 'Reloading' started by shade mt, Feb 12, 2012.

  1. shade mt

    shade mt Active Member

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    first question.

    i have a custom 7mm mag built on a argentine mauser 98 ,09 action, 26" barrel...super, super accurate..i mean like out of the ordinary accurate...here is the deal...i also owned a 7mm in a savage. This custom gun will NOT! chamber shells that were shot out of the savage. And it's really hard to full length size them enough. The only way i can resize them enough is by adjusting the sizer die down so far i can barely cam it over when i run the case up....The thing that baffles me the most is i bought a couple boxes of new Rem ammo that chamber in and out perfect...Why am i having such a hard time sizing cases that were shot in another rifle? The new empty's shot out of the custom chamber fine and will require nothing more than neck sizing... baffled on the resizing

    second question

    if this custom gun has that tight of a chamber...will the pressure be higher for any given load?..using less powder to achieve the same velocity as in say the savage?

    i haven't spent a lot of time with this gun yet..it also has a stock that don't fit me very well..(see thread in gunsmithing)...but i need to get this rifle up and running...shoots way to good to be sitting around.
     
  2. larrywillis

    larrywillis Well-Known Member

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    shade mt .....

    first question

    You've described a very common problem that happens whether you're loading for a dozen rifles or just one. Your case width above the belt just requires a bit more resizing. Read up on the Belted Magnum Collet Resizing Die. It's designed specifically for belted magnum handloads that don't chamber.

    second question

    There are several reasons why each and every chamber develops pressure differently. That's why it's a good idea to work up loads slowly.
     

  3. shade mt

    shade mt Active Member

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    thanks larrywillis

    i'll check that out..
     
  4. shade mt

    shade mt Active Member

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    checked it out and although the die seems like a good idea. i'm not 100% sure its necessary. I shoot a number of belted mags. This is the first time iv'e ever encountered this. Normally i use the same brass in each rifle..i was just baffled as to why i could not resize them to work...By using only brass shot out of that particular rifle and neck sizing..i should be ok....thanks for the info though...and i wouldn't mind buying one. whether necessary or not.
     
  5. larrywillis

    larrywillis Well-Known Member

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    Shade mt .........

    Using ordinarey calipers, measure the diameter of your resized cases just above the belt. Be sure to use the wide part of your blade. Then compare that to a new unfired case. See what you get ......
     
  6. BountyHunter

    BountyHunter Writers Guild

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    Larry is right, it is extremely common for brass fired in one gun not to chamber in another even after FL sizing.
     
  7. Edd

    Edd Well-Known Member

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    For several years I had three 7mm Rem mags, two Kimber model 89's and a Remington custom shop 700C. Once fired cases from my model 700 would not chamber in either of the Kimber rifles. I'm guessing if you try your cases from the Savage to other custom 7mm's you will find those cases won't chamber in them either. I'd also guess they will chamber fine in my model 700.
     
  8. larrywillis

    larrywillis Well-Known Member

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    Quality handloads require measuring.

    It's best to not guess if your handloads will chamber. When belted magnum cases bulge, they can be measured with ordinary calipers. The shoulder clearance of your handloads can also be easily measured with the Digital Headspace Gauge.

    Even when you're loading for just ONE rifle, your cases usually bulge above the belt - sooner or later. This bulge doesn't happen in the chamber, and it never happens on the first firing. This case bulge happens during the reloading process because of a weakened area just above the web (solid part of the case).

    This is how it happens . . . . .

    Factory belted ammo headspaces on the belt, and the shoulder gets blown forward .015" to .025" at the very first firing. That stretches, thins, and weakens belted cases far more than any non-belted case will ever experience. After that, the cumulative wear from reloading (pushing downward on the case) eventually causes a bulge at the weakest place - just above the belt.

    Unlike factory ammo, handloads MUST headspace on the shoulder.
     
  9. Bart B

    Bart B Well-Known Member

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    Re: Quality handloads require measuring.

    I disagree.

    I've worn out three .30-.338 barrels (two standard and one with the Keele version using .300 Win Mag cases) and accuracy with new and resized fired cases was the same. Fired cases were double sized (first time with a standard full length sizing die setting the shoulder back just enough to permit headspacing on the belt then a body die to reduce the ridge in front of the belt back to new case diameter; same thing the Willis collet die does) Accuracy for both new and resized cases with 20+ shot groups at 1000 yards was well under 7 inches. I'm not the only person to get such results; there are others.

    Back when the 30 caliber magnums were "the" cartridge for long range matches, the above methods resulted in virtually of the match winning and record setting scores.
     
  10. Loner

    Loner Well-Known Member

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    The cases I have had stick from being to large in the od really stick. And the bolt opens
    until the extractor hits the rim and then stops like it hit a wall. A case that is head spaced
    too long will just cause a hard bolt lift from the beginning of it's movement until the
    pressure comes off. I suggest another shell holder with a few thousands taken off if you
    have to reuse the cases. I can't stress enough to etch , dipple, blue or what ever else
    you have to do to mark that modified shell holder from your stock one. You'll ruin a lot
    of brass if you don't.
     
  11. larrywillis

    larrywillis Well-Known Member

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    Loner ........

    Grinding down your shellholder allows your sizing die to push the case shoulder back too far. When your problem is excessive case WIDTH, this does nothing to help your handloads fit better.

    Here's what happens when you push the shoulder more than .002"

    When your round is fired, the brass stretches even farther as it expands to fit the chamber. This cumulative stretching (at each firing) thins your brass until it is paper thin. This thinned brass makes is even easier to bulge during the reloading process. Your cases still won't chamber; and if they do, you'll experience case head separations.


    [​IMG]
    Picture from WWW.LARRYWILLIS.COM
    This picture shows a cut-away view of a belted case that had the shoulder pushed back too far. It was stretched (after 3 firings) until it became dangerously thin.

    It's always best to "measure" your cases, to determine why your handloads don't fit.


     
  12. shade mt

    shade mt Active Member

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    i never really ran into this problem before simply because i usually never mix brass between rifles.
    As noted above brass that was fired from this rifle alone ...chamber in and out fine.
    I fully understand your concept of the case bulging above the belt.
    I guess i just never ran into the resizing problem before because i usually don't mix brass.
    At this point i'm curious to see what happens to brass that is fired in this rifle alone and neck sized only.
    I could be wrong , but i don't anticipate any problems. i should be able to as usual , get several loadings from brass, as long as i don't try resizing brass from other rifles.
     
  13. larrywillis

    larrywillis Well-Known Member

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    shade mt ........

    You could be right if several means 3 to 5 firings. If you don't want to measure your chamber clearance at the shoulder (and set your die height accurately), then it would definitely be better to just neck size.

    However, I know of about 4,000 shooters that would disagree with your last statement.
     
  14. Bart B

    Bart B Well-Known Member

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    While neck only sizing of bottleneck cases is popular, the folks that probably have done the most testing for accuracy with both belted and rimless bottleneck cases have been full length sizing fired cases setting their shoulder back a few thousandths. They now use Redding full bushing dies for cartridges they're made for and Redding standard full length sizing dies for the rest. Very few folks shoot their bullets as accurate as they do from test barrels chambered to SAAMI specs. I'm referring to Sierra Bullets, who have been full length sizing all their cases used to test their products for accuracy since the 1950's.