To crimp or not to crimp?

[fischfam]

I recently started reloading my ammo and am using a Lee single stage hand press so speed is not really an issue here but I have a question for you all. I have both .38 and .45 caliber dies in the 4 die set. These come with the last one being a factory crimp die, although I think that this is new either this year or last. So I am thinking that for my .45's 'yes' if really does matter and it rolls the edge very nicely but for the .38/.357 is it really necessary or can I just skip this step since the seating / crimping die looks like it really seats the bullet firm. I am thinking that up until they just came out with these dies no one was factory crimping their .38's. Unless there is a reason to crimp them such as creating more pressure on exit of the bullet from the case or something like that, I am not sure if it makes a difference. (I haven't tried the two differences at the range yet and everything I am loading is factory crimped, in case it really matters.)

[hornady]

I don’t crimp most of my rounds. The exception is Hunting rounds. Or hot load In the revolver. Most mild load will not effect the rounds in the cylinder.. Autos you will need a crimp . A crimp will increase pressure. .Its also harder on the brass

[Xringshooter]

A .38/357 headspaces on the rim of the case and if a heavier load is used you need the roll crimp in the channelure to insure the bullet doesn't move under recoil. If a light load you may just need to have it set enough to remove the bell on the mouth. You don't want the bullet to come out during firing, especially in a revolver because it could jam the cylinder.

The .45 (I am assuming it is a .45ACP) headspaces on the case mouth so you DO NOT want to use a roll crimp on it to hold the bullet. Rounds designated for semi automatics need a taper crimp to hold the bullet and still have a clearly defined case mouth to correctly headspace.

If the .45 is a .45 Colt. You treat it the same as you would the .38/.357.

[bert]

Roll crimp the .38, taper crimp the 45 if it is acp. .45 long colt roll crimp. With higher loads the bullet can come unseated during recoil. The bullets in the cylinder. Taper crimp the automatics to insure closing the results of the expander die. A light crimp will do. Also use a case gauge with your auto loads.

[JoeWilliams]

The Lee Factory Crimp Die is a taper crimp, and a nice one. I found my accuracy is more consistent using the factory crimp die... it won't over crimp, and will actually resize the case one more time, tending toward better reliability with your ammo as well. So, yeah, I do use the factory crimp die.

[Jim1911]

With my many days of experience, if it is going in a semi-auto, I always use the factory crimp die. Some loads the crimp is just enough to straighten out the flair from the sizing die. Some loads I use it for a firm grip but ensure a good seat in the chamber. I tried a batch with using it. The pronounced lip got stuck on anything it could.

Target loads with the 38, I don't bother.

[eulogyADD]

A crimp will increase pressure. .Its also harder on the brass

According to the Lee manual, a crimp only increases the pressure by 100 or so psi. So firing a crimped round when the pressure is already in the 10's of thousands psi, it wont really make much of a difference.

[Dave_n]

Easy rule of thumb. If a rimmed case, roll crimp (R in case nomenclature = roll in crimping), if a SR or no rim, taper crimp. Lee's crimp dies are specific to calibre, so quite easy. Dave_n

[WVBob]

I like the taper crimp on a .38/.357 mag. You never get to much roll and have one that does not want to chamber. I started reloading using the roll crimp but about ten years ago went to the taper or factory crimp for everything.