Poor Crimp in 9mm and .45ACP

Coolray · December 20, 2000, 10:37 AM

I know how to tell if my crimp is poor with my revolver ammo.
I need to know what is to much crimp and what are the signs of to much taper crimp?

It seems to me that the fellow teaching me cuts corners,I have stopped having him help me.

I figured it out when I compaired the revolver crimps (factory) and the ones we had just done and we actually puched the case a little below the crimp,when I mentioned it to my friend he asked if the rounds will chamber....I checked they did,so he said then they are O.K. I think I prefer a more factory look. "It'll work" is just not good enought for me. I have also just learned that he has never loaded Taper crimp ammo. I don't want to learn the hard way I know I load to OAL I just need a tip or two about crimping. I'm using the Lee carbide die set that is a taper crimp.

MADISON · December 20, 2000, 01:07 PM

Here is how I tell if there is enough crimp:
1. Load a round.
2. Find a flat hard surface.
3. Place the loaded round nose down on the surface.
4. Press hard on the bullet--If the bullet does not go into the case, there is enough crimp.

Jerry Stordahl · December 20, 2000, 02:47 PM

Coolray: You don't want to get too excessive with the crimp on .45 & 9mm cases. They have to headspace on the mouth of the case. Use just enough to keep the bullet from sliding into the case under pressure. Madison is right.

Steve Smith · December 20, 2000, 03:32 PM

I don't know about 9mm, but for .45 acp you can jsut about bet that if your crimp measures .470" or less, it's too much. My setup has them crimped at .471". Like Jerry said, it headspaces on the mouth, so you don't want to crimp it too much.

Coolray · December 20, 2000, 05:21 PM

Thanks,
So on the .45 I should measure to .471 no smaller? After I seat the bullet then adjust the die in 1/4 turns to achieve the desired crimp?

drothen · December 20, 2000, 07:17 PM

My 9mm Luger crimp is 0.377, depending on the brass I am using. Since 9mm is a tight fit to the brass, I actually measure the outside diameter of the brass where the bullet has been pressed in and make the taper crimp between 0.001 and 0.002 less in diameter. I check by trying to push the bullet in, as noted in the other posts.

Most reloading books caution about overcrimping 9mm because it can increase pressure significantly. It can also be easy to put enough powder in to compress the load, resulting in the same problem.

Steve Smith · December 20, 2000, 07:41 PM

I don't think .001" will kill you, either way. As I said, I am crimping to .471" with very good results. That's with a .452" bullet, mind you. You may have .451" bullets. Measure to be sure. .473" is max per SAAMI specs. The bullet dia. will affect the crimp measurement. If the mouth of the case looks "bevelled in" toward the bullet, there's too much crimp. Take a look at a factory round, and you'll see that the case mouth is straight, and you can't see a "crimp." That's what you want. I've heard some folks say that taper crimping is what you do to remove the bell or flare. That gives you an idea of what the crimp does...it DOESN'T hold the bullet in (the case does that) it jsut takes the bell out. True, if you don't have it crimped tight enough, you could probably push the bullet in by leaning on it, but that's that a really scientific test. Once you get your crimp around .471"-.473" then take your fiing pin out and put one in the magazine and cycle it. If you can cycle the same one two or three times with out changing the OAL very much, then you're fine. (Mine don't move at all)

December 20, 2000, 10:37 AM	#1
Coolray Senior Member Join Date: August 10, 2000 Location: Spokane ,wa Posts: 290	I know how to tell if my crimp is poor with my revolver ammo. I need to know what is to much crimp and what are the signs of to much taper crimp? It seems to me that the fellow teaching me cuts corners,I have stopped having him help me. I figured it out when I compaired the revolver crimps (factory) and the ones we had just done and we actually puched the case a little below the crimp,when I mentioned it to my friend he asked if the rounds will chamber....I checked they did,so he said then they are O.K. I think I prefer a more factory look. "It'll work" is just not good enought for me. I have also just learned that he has never loaded Taper crimp ammo. I don't want to learn the hard way I know I load to OAL I just need a tip or two about crimping. I'm using the Lee carbide die set that is a taper crimp. __________________ Hello My name is Coolray.............And I'm an Addict

December 20, 2000, 01:07 PM	#2
MADISON Senior Member Join Date: January 1, 2000 Location: Roanoke, Virginia Posts: 2,678	Proper taper crimp Here is how I tell if there is enough crimp: 1. Load a round. 2. Find a flat hard surface. 3. Place the loaded round nose down on the surface. 4. Press hard on the bullet--If the bullet does not go into the case, there is enough crimp.

December 20, 2000, 02:47 PM	#3
Jerry Stordahl Member Join Date: July 9, 2000 Location: Halstad, MN USA Posts: 96	Coolray: You don't want to get too excessive with the crimp on .45 & 9mm cases. They have to headspace on the mouth of the case. Use just enough to keep the bullet from sliding into the case under pressure. Madison is right.

December 20, 2000, 03:32 PM	#4
Steve Smith Senior Member Join Date: December 9, 1999 Posts: 4,131	I don't know about 9mm, but for .45 acp you can jsut about bet that if your crimp measures .470" or less, it's too much. My setup has them crimped at .471". Like Jerry said, it headspaces on the mouth, so you don't want to crimp it too much.

December 20, 2000, 05:21 PM	#5
Coolray Senior Member Join Date: August 10, 2000 Location: Spokane ,wa Posts: 290	Thanks, So on the .45 I should measure to .471 no smaller? After I seat the bullet then adjust the die in 1/4 turns to achieve the desired crimp?

December 20, 2000, 07:17 PM	#6
drothen Senior Member Join Date: November 4, 2000 Posts: 104	My 9mm Luger crimp is 0.377, depending on the brass I am using. Since 9mm is a tight fit to the brass, I actually measure the outside diameter of the brass where the bullet has been pressed in and make the taper crimp between 0.001 and 0.002 less in diameter. I check by trying to push the bullet in, as noted in the other posts. Most reloading books caution about overcrimping 9mm because it can increase pressure significantly. It can also be easy to put enough powder in to compress the load, resulting in the same problem.

December 20, 2000, 07:41 PM	#7
Steve Smith Senior Member Join Date: December 9, 1999 Posts: 4,131	I don't think .001" will kill you, either way. As I said, I am crimping to .471" with very good results. That's with a .452" bullet, mind you. You may have .451" bullets. Measure to be sure. .473" is max per SAAMI specs. The bullet dia. will affect the crimp measurement. If the mouth of the case looks "bevelled in" toward the bullet, there's too much crimp. Take a look at a factory round, and you'll see that the case mouth is straight, and you can't see a "crimp." That's what you want. I've heard some folks say that taper crimping is what you do to remove the bell or flare. That gives you an idea of what the crimp does...it DOESN'T hold the bullet in (the case does that) it jsut takes the bell out. True, if you don't have it crimped tight enough, you could probably push the bullet in by leaning on it, but that's that a really scientific test. Once you get your crimp around .471"-.473" then take your fiing pin out and put one in the magazine and cycle it. If you can cycle the same one two or three times with out changing the OAL very much, then you're fine. (Mine don't move at all)