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How do you know when you have a sufficient crimp. I am reloading 40 S&W to OAL of 1.120 and am not sure about the crimp...


NM Hunter
How do you know when you have a sufficient crimp. I am reloading 40 S&W to OAL of 1.120 and am not sure about the crimp...

There is a letter to the editor in the current HANDLOADER magazine that addresses this question. Since you are asking about an autoloader cartridge the answer is fairly simple. Your crimp is most likely going to be a taper crimp, that is what all of the current dies I'm aware of are producing now. That being the case, look at the SAAMI drawing in your loading manual or on-line and you will see the correct loaded cartridge case mouth diameter and that is where you should set your crimp die. Measure with a blade caliper.

If the bullets you are using are undersized for that then you'll have to get a different bullet. If they are too large then you will probably have a bulge in the case at the base of the bullet. If that keeps the ammunition from seating in the chamber then a pass through a Lee Factory Crimp Die should cure that problem.

Good loading and good shooting!

Red Hat

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You don't want a heavy crimp on your 40's just enough to hold the bullet in place. Like 45acp 40S&W rounds are headspaced on the mouth of the case that's why I like Lee's factory crimp dies. For about $15 they are a must for auto rounds. They resize the case after seating the bullet which take the slight bulge out that sometimes happens when seating the bullet. I love the positive feel when adjusting the crimp setting. Link Removed


With a semi auto round like the .40 or .45ACP, you are using a taper crimp because the round headspaces off the case mouth. You can't roll crimp it because that means there is no case mouth available to head space off of because you just rolled it into the bullet or into a crimping cannelure. Basically, it means you are holding the bullet in place solely by friction. If you overdo the crimp, you'll see a band of distorted brass right at the case mouth where too much brass has been forced into contact with the bullet. Too little crimp, on the other hand, means you can end up with bullet jump under recoil and that can lock up your pistol. It will also result in erratic velocities, dirty cases, blowback of gasses and unburned powder being left in the gun.

What I do to set the crimp is I set it up (using dummies) with too much crimp and back it off until the 'banding' that means I have too much crimp disappears. That's one reason I went to crimping as a separate stage rather than seating and crimping at the same time.

I've used the LEE Factory Crimp Die a lot when using a progressive press (for several rimmed revolver cartridges and .45ACP) but I find I don't need it for a single stage. You can get the same crimp by using the seater die with the seater plug and knob pulled in a process separate from bullet seating.


I'll second the Lee Factory Crimp dies. I have them in just about every caliber that I reload for. A well designed, affordable, easy to use product. Bill T.


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How much crimp?

For me, the simple answer is to first look at the round whose bullet you have just seated. Typical auto-load handgun rounds needed a little belling on the case mouth, right? Now, get rid of that belling, crimp it in with your next step, and look again! Belling gone? But, you ask, how tight? Since, as those who have already answered stated, your crimp is a friction hold, take the finished round in your hand and press the bullet end into the counter--hard! Measure your change?... no movement of the bullet into the case? You're done.
I checked with the peeps at Dillon Precision (in person) and that simple "press test" is all you need. Again: Adjust your die to that point where the belling is neutralized and you cannot move the bullet into the case with a strong hand press.

SC Tiger

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If they are too large then you will probably have a bulge in the case at the base of the bullet. If that keeps the ammunition from seating in the chamber then a pass through a Lee Factory Crimp Die should cure that problem.

Good loading and good shooting!

Are you referring to the ring around the case at the base of the bullet? I have factory 9mm ammo (Speer Gold Dot) that has that - it actually helps me tell the difference between my 124 gr and 115 gr loads.

I've never worried about crimp but I only reload for revolvers. That's the main reason I started with wheelgun ammo - figured I could learn the basics that way then get into crimps and case trimming after I have the basics down (on a revolver all that matters is that the bullet doesn't stick out the front of the cylinder).

I don't know about the crimp dies but I'll second Lee dies in general. Only ones I use. I use them in a RCBS SB2 press with the Hornaday Lock-n-load kit.


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Lee factory crimp dies are great. I buy one for all the handgun calibers i load. I use the 3 carbide die sets from lee, I add the forth being the factory crimp die.
Autos use a taper crimp, Revolvers use a roll crimp. The lee dies give you these crimps as they are caliber specific. No guess work, if you have a progresive turret type price, you add this to your tool head. This die will be the one after the seating die. You seat then you go to this next die and perform your crimp.

You can adjust the die for a light crimp or heavier crimp, by turning thr knob as you do with your seating die.What this die also does is make all your ammo universal as to function in all like caliber pistols. Hence the word "factory" in its normanclature. Basically it will make your auto and revolver rounds more reliable. When you start using these dies, you will notice that some rounds will feel like they are being crimped more than others.

Although you have the crimp knob setting at the top of the die at the same setting, some rounds will get more attention than others. My theory is that some of the brass might be that little bit longer than the rest. Or the bullet projectile is that little bit more or less in circumfrence.

All i know is that your ammo will be better in feeding and unerversal. Have you every given a reload to another shooter with a different make gun in the same caliber, and for some reason it does not feed right in his or visa versa?

That is the Factory aspect of the design at work. I do not have any go no go type guages for any of my reloads. I stay within the perometer of the OAL given in the load data, and respect to thier oal regarding different powders, as not to raise pressures. Not exceding the Max oal.

I have been reloading pistol ammo for 25 yrs, and use Lee dies exclusively. 4 dies to complete the process. I have been reloading rifle for a couple of years now and find the big difference is the rifle cases, especially the the AK and Ar shouldered cases stretch after following. This is mostly due to thier shoulder type cases and more powder resulting in higher pressures. So you need to trim, you rarely if every need to trim pistol brass.

Getting back on the crimping, i do not use a alot of crimp when i adjust the crimp die, they say the brass will last a little longer. I really do not know how many times you can reload a cartridge, depends on how hot you are reloading


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The other plus to crimping is your bullets will have a tighter grip on the case,which will aid in feeding up the ramp of the barrel and stripping off the round from the mags in autos of course.

In revolvers the advantage is the rounds that are not chambered the heads will stay put in thier brass. Especially with +p or magnum type loads. The crimp die has aided you by putting a roll crimp to these rounds. Have you every fired a round in a revover and the cylinder did not want to rotate to the next round after doing so. What happened was the round you just fired had pulled the head or heads out of the others because of the recoil of that fired round. I had this happen to me early on when i started relading. You will not be able to swing out the cylinder, if this happens. you will need to use some type of dowel that will push the head back in the shell making the round s oal shorter again, maybe more than on round in the cyclinder even.

When you do get it open you at first question yourself as to why or how did i make this round longer than the others. You will then relize that the wheelguns reputation to always go bang is not so. This rarely if ever happens with new factory ammo because all compotents of these round are using all new brass with cases that the mouths where never streched open from prior use.
This is why i never load to maxium charge when using once or more fired brass. If i wanted to make said rounds to equal factory power level rounds, i will buy new virgin brass and the expensive type projectiles to go in them.

At that point i never did the math, but i do not think i will be saving much money per round. Hey i gave up thinking a long time ago that i can make better ammo than the high quality factory stuff, i can make damn good reliable ammo. And i do with a nice saving in cost compared to the price of most commercial ammo.

I know, a little more than you were asking in this thread but hopefully it makes sense and saves you some grief and gets you to making some better ammo, It is a great hobby,

Good luck in all your reloads, Steel Hammer

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