Taper Crimp

LAR15 · March 18, 2008, 06:44 PM

Need some help with the taper crimp using Rainier 180gr plated bullets. I know that you have to watch for overcrimp when using these softer bullets and that is what I seem to be having trouble with. I'm pulling the bullets after running through the press trying to check for overcrimp.

I'm loading 40 S&W with RCBS dies in a Dillon 550b. The taper doesn't seem to wanna go under .424 or it really looks to bite into the bullet. I'm a bit concerned that it is just not enough taper. On the other hand the idea of overcrimping and getting it down to .421 seems much worse.

Question is what is your OD around the crimp with these rounds?

I appreciate the help.

ShootingNut · March 18, 2008, 07:18 PM

I load with Lee equipment. Using their FCD I just lightly crimp my .40's to take "the sharp mouth edge" off and snug the casing to the bullet. Seems to be all my M&P needs, as it feeds great and shoots very well.
I may be wrong, but some folks seem to over crimp more than not.
Regards,
SN

LAR15 · March 18, 2008, 07:23 PM

Could you measure the OD around the crimp and let me know what you are shooting? I appreciate it.

Shoney · March 18, 2008, 09:41 PM

You must first understand that the 40SW is designed to head space off the front edge of the case. What that means is the case stops it's forward progress in the chamber when the rim of the case hits the front edge of the chamber.

If you crimp the front outside diameter of the case less than 0.400", the case will slide beyond the chamber, and if the firing pin does strike the primer, either an over pressure load may result or it will slam into the slide face and eventually may cause damage.

Begin the taper crimp by just removing the bell of the case, then test it by pushing it against your bench with sufficient force to see if the bullet sets back into the case. Next test is to load a magazine and fire them one at a time examining each newly chambered round to make sure the bullet has not been set back.

Usually the resizing die reduces the case diameter enough that no additional crimp is required beyond simply removing the bell.

March 18, 2008, 06:44 PM	#1
LAR15 Junior Member Join Date: October 20, 2007 Posts: 6	Taper Crimp Need some help with the taper crimp using Rainier 180gr plated bullets. I know that you have to watch for overcrimp when using these softer bullets and that is what I seem to be having trouble with. I'm pulling the bullets after running through the press trying to check for overcrimp. I'm loading 40 S&W with RCBS dies in a Dillon 550b. The taper doesn't seem to wanna go under .424 or it really looks to bite into the bullet. I'm a bit concerned that it is just not enough taper. On the other hand the idea of overcrimping and getting it down to .421 seems much worse. Question is what is your OD around the crimp with these rounds? I appreciate the help.

March 18, 2008, 07:18 PM	#2
ShootingNut Senior Member Join Date: December 27, 2006 Location: Wisconsin Posts: 1,475	I load with Lee equipment. Using their FCD I just lightly crimp my .40's to take "the sharp mouth edge" off and snug the casing to the bullet. Seems to be all my M&P needs, as it feeds great and shoots very well. I may be wrong, but some folks seem to over crimp more than not. Regards, SN

March 18, 2008, 07:23 PM	#3
LAR15 Junior Member Join Date: October 20, 2007 Posts: 6	Could you measure the OD around the crimp and let me know what you are shooting? I appreciate it.

March 18, 2008, 09:41 PM	#4
Shoney Senior Member Join Date: February 21, 2002 Location: Transplanted from Montana Posts: 2,311	You must first understand that the 40SW is designed to head space off the front edge of the case. What that means is the case stops it's forward progress in the chamber when the rim of the case hits the front edge of the chamber. If you crimp the front outside diameter of the case less than 0.400", the case will slide beyond the chamber, and if the firing pin does strike the primer, either an over pressure load may result or it will slam into the slide face and eventually may cause damage. Begin the taper crimp by just removing the bell of the case, then test it by pushing it against your bench with sufficient force to see if the bullet sets back into the case. Next test is to load a magazine and fire them one at a time examining each newly chambered round to make sure the bullet has not been set back. Usually the resizing die reduces the case diameter enough that no additional crimp is required beyond simply removing the bell.