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Bulleting and Crimping Stage of Reloading Ammunition |
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Bulleting and crimping of reloaded ammunition rounds are usually combined into one operation that uses a two function die.
Bullet seating punches have noses that are shaped internally to match the bullet that they are intended to be used with, these may be purchased from die manufacturers or machined from blank punches by the reloader.
Many bottleneck cases do not require a crimp as the friction fit of the case mouth can be sufficient hold the bullet in place. Crimping the mouth of the case causes fretting and shortens case life.
Seating bullets requires accurate adjustment of the seating punch...
- place a resized and trimmed case that has been re-primed and contains the requisite amount of powder into the shell holder and run the ram to the top of the stroke.
- Screw the bullet seating die down into the press until you feel the crimping shoulder touch the case mouth.
- Back off the die half a turn and set the die body locking ring. (Not shown in the drawing.)
- Adjusting the seating punch inside the die to seat the bullet to the correct depth in the case will depend on the type of bullet that you are using, the length of the rifle's magazine, the amount of lead in the chamber throat and whether the reloaded cartridge may be fired in different rifles. Insert a bullet into the mouth of a prepared case and slowly run the case into the seating die with the seating punch manually adjusted to a shallower depth than you expect will be correct. You will feel the bullet contact the punch and be pushed a short way into the case. Withdraw the case and measure how far the bullet protrudes from the case, as you know the pitch of the threads on the seating punch, you can calculate how far to screw the punch inwards. Keep checking and making finer and finer adjustments until the cartridge overall length is correct to specification.
- Remove the seating punch from the press, wipe the threads with a tissue, run the correct length cartridge all the way into the seating die. Screw the punch into the die until it makes firm obvious contact with the bullet and tighten the locking collar.
- Take a second resized and trimmed case that has been re-primed and contains the requisite amount of powder and seat a bullet, then remove the round and check the overall length meets the specification.
- Checking the fit... Take the newly reloaded cartridge and chamber it in your rifle, observing all possible safety precautions. Also insert it into the magazine to ensure that it fits and work the cartridge slowly through the action to check that it feeds correctly. If it doesn't, re-adjust the seating punch until it does. When a reloaded cartridge chambers and feeds correctly in the weapon, the bullet seating die is correctly adjusted for that loaded case/bullet combination.
Revolver cartridges generally require crimping to hold the bullet firmly in place during recoil, such bullets must have a crimping cannelure to act as a receptacle for the crimp.
Consistent roll crimping relies on the cases being identical in length, wall thickness and chamfering.
For bullet seating and crimping in one operation, adjust the seating die as follows...
- Place a resized and trimmed case that has been re-primed and contains the requisite amount of powder into the shell holder and run it to the top of the ram stroke.
- Screw the bullet seating die down into the press until you feel the crimping shoulder touch the case mouth.
- Back off the die half a turn and set the die body locking ring. (Not shown in the drawing.)
- Lower the prepared case and place a bullet in the case mouth. Run the case with bullet slowly into the die, stopping frequently to check the bullet seating depth as the bullet is pushed into the case. Adjust the seating punch up or down so that, at the top of the press stroke, the bullet is seated with the case mouth in the centre of the cannelure of the bullet.
- Remove the bullet seating punch temporarily. Run the un crimped cartridge to the top of the stroke and loosen the die body locking ring. Screw the body of the seater die into the press until you feel the crimping shoulder touch the mouth of the case. Lower the un crimped cartridge and turn the seating die down approximately 1/8 of a turn. Raise the prepared cartridge fully into the seater die and check the crimp. Refine the adjustment of the die until you are satisfied with the strength of crimp, then tighten the die body locking ring.
- Wipe the threads of the bullet seating punch with a tissue, run the satisfactorily crimped cartridge all the way into the seating die. Screw the punch into the die until it makes firm obvious contact with the bullet and tighten the locking collar.
Cartridges for auto pistols headspace on the case mouth and are generally taper crimped in order to retain this feature. Taper crimp bullet seating dies are specially marked by their manufacturers to differentiate from roll crimping dies.
The taper crimping feature is part of the die profile and the amount of crimp is determined by how far the seating die is screwed into the press. Cases to be taper crimped should all be the same length and wall thickness, but bullets do not require a crimping cannelure.
- place a resized and trimmed case that has been re-primed and contains the requisite amount of powder into the shell holder and run the ram to the top of the stroke.
- Screw the bullet seating die down into the press until you feel the crimping shoulder touch the case mouth.
- Back off the die half a turn and set the die body locking ring. (Not shown in the drawing.)
- Lower the prepared case and place a bullet in the case mouth. Run the case with bullet slowly into the die, stopping frequently to check the bullet seating depth as the bullet is pushed into the case. Adjust the seating punch up or down so that, at the top of the press stroke, the bullet is seated to the correct cartridge overall length as specified in your reloading manual or weapon manufacturer.
- Remove the bullet seating punch temporarily. Run the un crimped cartridge to the top of the stroke and loosen the die body locking ring. Screw the body of the seater die into the press until you feel the crimping shoulder touch the mouth of the case. Lower the un crimped cartridge and turn the seating die down approximately 1/8 of a turn. Raise the prepared cartridge fully into the seater die and check the crimp. Refine the adjustment of the die until you are satisfied with the strength of the taper crimp and the way the round chambers in the weapon, then tighten the die body locking ring.
- Wipe the threads of the bullet seating punch with a tissue, run a satisfactorily crimped cartridge all the way into the seating die. Screw the punch into the die until it makes firm obvious contact with the bullet and tighten the locking collar.
- After tightening the locking collar make a second round and check that it is identical with the first sample.
Notes...
- When adjusting overall cartridge length, the bullet must not touch the rifling when chambered.
- If reloading a type of round that may be used in several different weapons, the dimensions of whose chambers may be different. The safest procedure is to set the bullet to the cartridge overall length as specified in your reloading manual or to repeat the setting operation for each weapon and select the shortest as your standard for that group of weapons.
- If you have a factory loaded cartridge available, it can be used as the sample cartridge in setting up your die, providing that the bullet in the sample is identical top that which you intend to use.
- The crimping feature is machined into the seating die and the amount of crimp is determined by how far the die is screwed into the press. Bullets can be seated without crimping by setting the body of the die a half turn shy of the case mouth.
- Setting the seating die too far into the press will cause an aggressive crimping of the case and may result in bulging of the body of the case.
Written... 21 January 2007,
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