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Riddle me this, please,,,,,,

forgemonkeyforgemonkey Member Posts: 20,346 ✭✭✭✭
edited May 14 in Ask the Experts
Below is a fired case from the 25-25 Stevens. The primer is 'cratered' ,,,,,,, off centered strike due to firing pin traveling at an upward angle (which is normal). BTW, it's a tack driver,,,,,, :)

Which might be the the cause ???? Or maybe both ?
1. Too much pressure ? The formula for Trail Boss is to fill the case to the bottom of where the bullet will seat, weight this amount, and that's the max. load (7gr.). Multiply by 70% = 4.9gr. = starting load.
This was loaded with 5.5gr of TB.
2. The breach block locks up tight/flush when the 'lever' cams over. However, the rear(rim) of the case is a couple of thousandths below the end of the barrel. There is no rearward 'play' in the breach block when locked.
The primer was seated just below the rear of the case, after firing the spent primer is slightly 'above' the rear of the case, leading me to believe the case rim is too thin. Headspace ?????

Comments

  • BobJudyBobJudy Member Posts: 2,168 ✭✭✭✭
    I think you nailed it. Either the rim is out of spec or chamber cut a turn to deep. Case gripping the chamber upon firing allowing the primer to move back and extrude  into the firing pin hole. Bob
  • MIKE WISKEYMIKE WISKEY Member Posts: 9,263 ✭✭✭
    AS ABOVE........with a 'high' pressure round like that nothing to worry about
  • rufe-snowrufe-snow Member Posts: 18,461 ✭✭✭
    You might try loading the bullet so it touches the rifling. This might alter the headspace enough, to have an effect on the primer?Since this will increase pressure, I would drop the load by half grain.
  • TRAP55TRAP55 Member Posts: 7,969 ✭✭✭
    edited May 15
    Forge, was that the first time that brass was fired? If not, did you full length, or neck size?
    TrailBoss is a low pressure powder, I've compressed loads, and never got primer flow at all, much less like that. Headspace issue should leave a ring around the base of the brass, does it have one?
    Any powder burn on the outside of the case around the neck?
    What primers you using?
  • forgemonkeyforgemonkey Member Posts: 20,346 ✭✭✭✭
    TRAP55 said:
    Forge, was that the first time that brass was fired? If not, did you full length, or neck size?
    Yes, first time. Ironic, using the FL sizing die and seating the bullet left the case bulged and would not chamber without resizing the live round. Thus, I loaded a few without sizing, no problem chambering. And groups are excellent,,,,,,go figure.
  • charliemeyer007charliemeyer007 Member Posts: 7,348 ✭✭✭
    You could try and cut some brass shim stock washers to place on the front side of the rim.  Use a hole punch for the inside and scissors or a knife to trim the outside.  Or drill some brass stock to the correct ID and then turn the correct OD finally part it off to the correct thickness.  I would also consider running a bead of solder on the front of the rim and then turning the case to correct rim thickness.

    You could machine a washer to shim the barrel.  Over-sized OD and then cooled on dry ice might provide enough of a  good enough fit to hold it place.

    Did you make the new fitted firing pin or bush the breach block?
  • forgemonkeyforgemonkey Member Posts: 20,346 ✭✭✭✭
    Charlie, haven’t taken the time to turn a new pin,,,,,,,but it’s next on the list. I will reduce the powder load and see if that helps.
  • nononsensenononsense Member, Moderator Posts: 10,587 ******
    Please check the difference between the firing pin diameter and the FP hole in the breech block. This appears to be a low pressure extrusion of the primer into a larger diameter firing pin hole.

    Best.

  • forgemonkeyforgemonkey Member Posts: 20,346 ✭✭✭✭
    Please check the difference between the firing pin diameter and the FP hole in the breech block. This appears to be a low pressure extrusion of the primer into a larger diameter firing pin hole.

    Best.

    Yep, will use my numbered bit set for comparison.
  • XXCrossXXCross Member Posts: 1,306 ✭✭✭
    My two cents worth would say you have a classic example of a round that is producing too little pressure to drive the case back to the breach.  Try upping the load just a little. (emphasis on "LITTLE")  Go in small steps and see how far you have to increase to get the case to back out of the chamber.
    K.t.
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