" To crimp or not to crimp?"

[smokjunkee]

I believe I read somewhere that you don't put a crimp on certain handgun ammo. Is there any reason not to put one on say, 45ACP or 9mm.?
SJ

 

[Walkalong]

In general you would roll crimp revolver cartridges and taper crimp auto cartridges. Revolver rounds headspace on the rim of the case and auto rounds headspace on the case mouth. A good crimp is an important part of reloading for a number of reasons. That is the short answer.

 

[cdrt]

We just had a big discussion on another post about taper crimping .45 ACPs. The .45 and 9mm headspace on the case mouth unlike .38 Specials, etc. that have a rim; that's why I taper crimp them.
I have one of those drop in case gauges, but I taper crimp the .45 to between .470 and .472 and they work fine in both my 1911s and my Model 25 S&W w/o moon clips.
You can roll crimp the .45 ACP as long as your case mouth measurement is .460 and not smaller. I got that measurement from the old NRA reprint on the .45 Govt Model that has loading data in it.

 

[smokjunkee]

Ok, I'm a newbie. I don't have a single, live round loaded yet. So my second question is: What is the difference between roll & taper? I have the Lee 4-turet press with a factory crimp die. Will this do both?
SJ

 

[The Bushmaster]

Nope...If your Lee die set is for .45 ACP or 9mmX19 then it has a tapper crimp. If you have Lee revolver die set, they will give you a roll crimp...Remember that all you wnat to do with Auto ammunition is to remove the bell and no more. With revolver ammunition you want a firm crimp into the cannelure...Read your loading manual and if you have only one manual get at least one more...And read it too...

 

[the pistolero]

I remember reading somewhere that if you don't put enough crimp on a round, you'll end up with more unburned powder. That's been my only issue with my reloads so far..and getting those little grains out of the gun's nooks & crannies is a royal PITA, too. I need to work on that.

 

[The Bushmaster]

Pistolero...You are correct except that with auto ammunition one has to be careful not over crimp and loose that edge that the rounds needs to headspace on. If you are crimping revolver rounds pretty good and still have unburned powder granuals you may need to either use a little more powder or change powders to a cleaner burning one. Sometimes changing the primer to a magmum primer helps as long as you realize that you need to back off the powder charge by 10% and start over building the load. Not knowing what calibre you are having problems with isn't much help here either...Also whether you are using lead or jacketed bullets makes a difference as to what help we can do for you on that one...

 

[CMcDermott]

A taper crimp die is just slightly tapered inside, so as the case is forced up into the die it gets squeezed and the outside diameter is reduced. This leaves the end of the case square so that it can fit against the end of the chamber for proper headspace. That is why cdrt gave the neck diameter (.470-.472") of his finished cartridges as that is how you can determine if you have a proper taper crimp or not.
A roll crimp die rolls the case end over into a groove or canalure on the bullet, so the end of the case isn't square to the chamber. This crimp uses mechanical interference to help lock the bullet into place in the cartridge case. It can be used for rimmed, belted or necked cartridges that don't depend on the end of the case to determine the headspace in the chamber.
It is also much more difficult to determine if you have a good roll crimp or not as you just can't just measure the diameter of the case.
Here is a link to a thread on another forum that has some good pictures of some roll-crimps.
http://leverguns.sixgunner.com/topic.asp?TOPIC_ID=29794&whichpage=2

 

[the pistolero]

Sometimes changing the primer to a magmum primer helps as long as you realize that you need to back off the powder charge by 10% and start over building the load. Not knowing what calibre you are having problems with isn't much help here either...Also whether you are using lead or jacketed bullets makes a difference as to what help we can do for you on that one...

So far the only caliber I've been loading for is 10mm, with 155-grain Hornady XTP and AA#9, with a Kimber Stainless Target II as my delivery platform. I've been loading so far only the minimum load according to Accurate data, which is 14.3 grains of No. 9 for the 155-grain bullet in front of a regular LP primer. I have the No. 13 Speer manual, and one of the loads listed for a 200-grain bullet has a magnum primer behind 14 grains of No. 9. I've heard some people say not to use magnum primers at all with it, but that particular load makes me wonder how it would do with a lighter bullet. Not that I am going to run out & load any of the 155-grainers I have now with magnum primers, but still I do wonder.

 

[Sunray]

Crimping on rifle cartridges is really only required for heavy recoiling cartridges and ammo for lever actions. Otherwise, neck tension is enough.
The .45 and 9mm require taper crimping only. The .45 moreso. Aids feeding.
Picture the case mouth with a slight taper. Taper crimp looks similar to this / \ . Roll crimping similar to this ( ){the top half only}. Nowhere near as severe either.
I've never bothered to crimp any 9mm. or .38 Special/.357 mag. I don't crimp any rifle ammo. Even ammo used in a semi-auto.