300RUM problems

Discussion in 'Reloading' started by pvanwyk, Apr 30, 2009.

  1. pvanwyk

    pvanwyk Active Member

    Dec 23, 2004
    I've been picking up some strange problems with my 300RUM reloads. would appreciate any help. Here are the details:
    Foster CO-Ax press
    Foster dies (FL sizing die)
    Rem brass (twice fired)
    220gr SMK bullet
    CCI mag primer
    Local powder (South African)

    I've sorted the cases by uniform case thickness and weight. All cases have been trimmed to uniform thickness, just below max length.

    The case won't chamber 100%. The case slides forward into the chamber until it seems that the shoulder of the case or neck enters the neck / shoulder part of the chambering then there's trouble. This never happens with new unfired cases.

    It seems to me that there is a doughnut effect at the junction between the case body and shoulder. This does not happen with every case, probably 1 in 5 cases. Sometimes this doughnut is not visible to the eye. (it is also quite possible the this may not be the problem and that I'm missing something else).

    Can anybody shed some light oin what's happening ? Is it possible on seating the bullet that the bullet is pushing down on the neck thus deforming the shoulder ?
  2. AJ Peacock

    AJ Peacock Well-Known Member

    Oct 7, 2005

    Probably your problem, unless your sizing die is dirty and doing the same thing. Is it a new die? Did you clean it? What kind of lube are you using? Do they ALL chamber before seating a bullet? Do you have a sizing ball on the decapping pin?

  3. woods

    woods Well-Known Member

    Jun 4, 2006
    A couple of questions:

    You said the do-nut is at the junction of the case body and shoulder. Normally a do-nut is on the inside of the case and is at the junction of the shoulder and neck

    and obstructs the passage of a bullet below that point on a fired case. Is this the do-nut you are talking about? If not, can you post a pic? I'd like to see one at the case body/shoulder junction.

    Second question would be how are you setting up your dies? i.e. are you threading them in till they hit the shell holder, a little further or a little less?
  4. pvanwyk

    pvanwyk Active Member

    Dec 23, 2004
    thanks for the replies. The "doughnut" is between the shoulder and case body on the outside (from what I have seen) and not in the traditional sense when neck trimming. Will post a pic later. (have not cut the necks)

    the setup of the dies is a good point. I have recently got a gauge to measure the set back of the shoulder but have not yet loaded ammo with the gauge. I had previously setup the dies by screwing in the body to the shell plate and then a touch further in.

    Will check if the die is dirty but that wouldn't expalin that only 1 in about every 5 is giving a problem. using Imperial sizing wax (?) and do have the sizing ball in.
  5. Jim Oliver

    Jim Oliver Well-Known Member

    Jan 2, 2007
    If your seating die is adjusted too deep into the press (bottom of the die bumps the shell holder or is too close to it), you may be accidently crimping the case mouth just a bit. If so, this "can" cause a slight bulge outward of the case right at the point where the neck begins to taper outward to become the shoulder.

    Could be something else, but this is worth a look.

  6. MagMan

    MagMan Well-Known Member

    Dec 20, 2002
    Double check to make sure you don't have the expander ball adjusted to high. The bottom of the expander ball should be closely in line with the hole in the side of the die (per directions).

    Try taking the expander out and size, see if you get the same problem.
  7. BountyHunter

    BountyHunter Writers Guild

    Jun 13, 2007
    My guess is you are sizing the shoulder down too far and creating a small microscopic ridge that you are seeing as the donut. Had this happen to me once. Mftr directions are designed to be lawyer proof and not conducive the max accuracy.

    Back the die off 1/8 inch and start back down sizing until they will just chamber. Also use a bump guage to measure, virgin, once fired and 3x fired. Normally by 3x, the brass has flowed to chamber dimensions.

  8. steve smith

    steve smith Well-Known Member

    Jul 4, 2001
    Seating die is not adjusted properly. Assuming that your using a standard bullet seating/crimp die. If you have the die to far down, upon seating the bullet the die trys to crimp the case mouth. Sierra matchkings don't have a cannalure for crimping and the result is the brass gets pushed back, bulging the shoulder.

    Easy fix! Back off 1/8 of a turn on the die.

    Been there and done that! I accidentally got a few 270win cases mixed in with a whole bunch of 30-06 brass. With the elliptical expander on the die I never noticed the fact that I was necking up to 30cal. Never did trim the brass so when I went to seat bullets the "longer 270win" cases bulged big time at the shoulder.
  9. Rum River

    Rum River Active Member

    Mar 31, 2009
    I just did something very similar on another caliber. Just like has been mentioned, turned out I had the seating die screwed in too far.

    I reset the die by first backing the die out so far there was no chance the cartridge mouth would touch the crimp shoulder inside the die.

    I put a prepared case in the press and ran the ram all the way up.

    Slowly screw the die into the press, you will definitely feel when the crimping shoulder in the die contacts the cartridge mouth.

    Back the die off 1/8 to 1/4 turn and set the lock ring.

    Adjust your bullet seating depth as required.
  10. pvanwyk

    pvanwyk Active Member

    Dec 23, 2004
    I think everyone's got it right. will experiment tonight. Amazing what a fresh perspective can do :)

    Many thanks for the help.
  11. zigliss

    zigliss Well-Known Member

    Nov 12, 2008
    Just a final thought - don't use too much resizing lubricant - just a light covering is all that is needed.

    Interested to know how you get on!