To Crimp or Not to Crimp?

[Zeke Menuar]

I am loading for a BC.  My current experimental loads are between 46-50 grs of AA2015 under the Remington 405 SP.  Does one need to crimp 45/70 in a single shot?  

ZM

[John Traveler1]

Crimping is not needed for a single-shot .45-70.   Factory ammo is crimped because of the variety of single shot and repeaters it may be fired in.

Your cases will last longer if you do NOT crimp and if you minimize the amount of flare (mouth belling) too.  Some BPCR shooters claim better accuracy from non-crimped ammunition.

What is important is that you at least straighten out the mouth flare so the cartridge chambers easily.  I do this as a minimum, but also like to add a "taper crimp" like on factory pistol ammunition.  For lever action repeaters and box magazine bolt guns, a heavy roll crimp is advised to prevent bullet movement from recoil and feeding impacts.

HTH
John

[John Traveler1]

Crimping is not needed for a single-shot .45-70.   Factory ammo is crimped because of the variety of single shot and repeaters it may be fired in.

Your cases will last longer if you do NOT crimp and if you minimize the amount of flare (mouth belling) too.  Some BPCR shooters claim better accuracy from non-crimped ammunition.

What is important is that you at least straighten out the mouth flare so the cartridge chambers easily.  I do this as a minimum, but also like to add a "taper crimp" like on factory pistol ammunition.  For lever action repeaters and box magazine bolt guns, a heavy roll crimp is advised to prevent bullet movement from recoil and feeding impacts.

HTH
John

[stuffit]

I've tried several approaches to this including "no crimp", slight roll crimp, moderate roll crimp, and a Lyman "short" taper crimp die.  The last approach give me the most consistant accuracy in my BC.  

I use almost exclusively cast bullets so a slight flare is necessary to achieve undamanged seating of these bullets (even the gas checked ones).  I've currently decided that I prefer the taper crimip just over the front driving band of most bullets (at least the ones I use) also aids in consistant accuracy.  My conjecture in regard to this is that it give a more consistant neck tension and more consistant "release" of the bullet when firing.
 :wink:
stuffit

[jgalar]

If you can seat the bullet far enough out so that it can touch the rifling (lead bullet) then don't crimp. If you can't get the bullet near the rifling a crimp would help.

With a jacketed bullet you dont want to engrave the bullet, but have it .015" or so away from the start of the rifling. If you can't then crimp.

[ricciardelli]

No crimp required.