Excuse my ignorance, but

[tooslo]

I've been reading some posts, and a couple of folks said they crimp to -.002 or -.003. Am I right to assume this means bullet+case thickness X(2) -.002?

Surely you'd have to sort case brands to do this. Is it that critical? I seem to find alot of conflicting info on preferred crimp on 9mm. From a crimp that doesn't deform the bullet at all to what is suggested above, which sounds tight.

[Chris Keen]

I dont set my crimp by numbers. I start out close to what I want my crimp to be, then I keep lowering it and pulling bullets until I get a slight ring (indent) around the bullet. Then I set it, and forget it.

[Sarge]

Standard answer for 9mm will be to only crimp enough to remove the bell. Which in most cases mic's at around .376 or so.

[Merlin Orr]

I know it sounds bad but I do mine by feel mostly now with pistol ammo. Visually you can crimp to where the edge of the brass is about 1/2 way indented into the bullet. By feel I can still feel a distinct "lip" of the brass but it is smooth enough to where it does not create a full width "ledge" that grabs your finger when you drag across it.

Works great for me... Does anyone else check the crimp like this?

[kaiserb]

I know it sounds bad but I do mine by feel mostly now with pistol ammo. Visually you can crimp to where the edge of the brass is about 1/2 way indented into the bullet. By feel I can still feel a distinct "lip" of the brass but it is smooth enough to where it does not create a full width "ledge" that grabs your finger when you drag across it.

Works great for me... Does anyone else check the crimp like this?

I check my crimp by feel and have the same thing. A slight ledge that you can feel with your finger, just barely crimped into the bullet. One thing to note, is that over-crimping will cause your accuracy to suffer.

[GrumpyOne]

I've pulled some of mine after loading ( alright, more than a few! ) and apparently, I just crimp enough to take the bell out. There is no "ring" or indentation on the bullet what so ever. I've never had an issue with bullet setback in 38 super, 40 S&W, 38/357, or 45ACP. I have had an issue with crimping too much when I first started reloading. When I crimped them too much, they would get jammed, with the case mouth going inside the barrel, instead of stopping at the end of the chamber. Total PITA to get the slide back open with that! Lesson learned.

[Flatland Shooter]

I set the taper crimp with a loaded round of WW White Box. Adjust to where the crimp die does not change the profile on the factory round. Run a few through a case gage and all should be well.

Bill

[High Lord Gomer]

I mic the width of the case near the middle of where the bullet has been pressed into the case. I then mic it right at the case mouth and try for 1 or 2 thousandths less.

On the .357 SIG I load (using both .357 Sig and .40 S&W brass resized) I crimp a lot more!

[RH45]

I know it sounds bad but I do mine by feel mostly now with pistol ammo. Visually you can crimp to where the edge of the brass is about 1/2 way indented into the bullet. By feel I can still feel a distinct "lip" of the brass but it is smooth enough to where it does not create a full width "ledge" that grabs your finger when you drag across it.

Works great for me... Does anyone else check the crimp like this?

I check my crimp by feel and have the same thing. A slight ledge that you can feel with your finger, just barely crimped into the bullet. One thing to note, is that over-crimping will cause your accuracy to suffer.

+1

I've pulled a couple of bullets over the years, and mine show no "ring" where the crimp should be, but, with some bullets, it appears that where they were inside the case, they are a little smaller.

[CocoBolo]

I am a Computer Scientist so I use a very scientific method on 9 mm. After a preliminary setting I take the loaded round and press the bullet against my reloading bench if it pushes in easily well it just isn't enough. So another 1/4 turn, then another test and so on till the bullet stays put. I'm loading 9 mm major and if I get one pushed in its probalby going to be ugly, aka a rupture of the brass. As it turns out this is going to be about .003 crimp. These are jacketed bullets. I probably over crimp but I have had no ill effects.

With lead you can reach this point sooner but then its a matter of the drop check, if you don't have enough crimp they won't fit the guage. On plated bullets this is where the crimp is critical to get right or the accuracy will be adversly affected.

And you are right each brand of brass is a little different and you just have to adjust so that most all of them fit the drop check.

Over crimping a lead or moly bullet will undersiZe it and cause a build up in the barrel and accuracy issues. Jacket bullets are very forgiving and just hard to mess up.

[kmitchl]

I use a combination of the CocoBolo and Merlin technique. Most important is not having a bullet set back. That's done with the two finger test on the loading bench. You MUST have enough grip on the bullet to keep the bullet from setting back. Second issue is getting the case mouth bell closed enough to clear the case gage and ensure the round feeds and chambers with no problem. That's the feel test. I've never been sucessful trying to measure the crimp particularly with mixed brass with varying wall thickness.

[LPatterson]

I've been reading some posts, and a couple of folks said they crimp to -.002 or -.003. Am I right to assume this means bullet+case thickness X(2) -.002?

Surely you'd have to sort case brands to do this. Is it that critical? I seem to find alot of conflicting info on preferred crimp on 9mm. From a crimp that doesn't deform the bullet at all to what is suggested above, which sounds tight.

The answer to your first question is yes, that is how it is figured. If you use this method then yes it is critical to sort. I prefer to sort but I have OCD. The method of setting a crimp and pressing it against the bench is where most of us came up with the amount of crimp needed. The more a bullet is crimped, the more it is deformed. So for accuracy with a bolt action rifle it would be no crimp. However with semiautomatic pistols, a bullet that moves back into the case upon loading can become a drawer changing event. So it becomes a compromise between bullet set back and over crimping. I prefer neither so I sort.

[G-ManBart]

If you seat a bullet and can push it deeper in the case before you crimp, you've got a problem. The "crimp" shouldn't determine whether you have enough neck tension (bullet pull is the correct term, but nobody seems to use it) or not. R,

Edit to add: This is only for cartridges that headspace on the case mouth. Heavy revolver loads are different, and crimp does matter.

Edited February 6, 2010 by G-ManBart

[tunakilla]

If you seat a bullet and can push it deeper in the case before you crimp, you've got a problem. The "crimp" shouldn't determine whether you have enough neck tension (bullet pull is the correct term, but nobody seems to use it) or not. R,

Edit to add: This is only for cartridges that headspace on the case mouth. Heavy revolver loads are different, and crimp does matter.

only crimp enough to remove the bell

[Duane Thomas]

It's not the crimp that prevents bullet setback. It's the fact that the diameter of the casing is smaller than the diameter of the bullet, thus when the bullet expands the casing down to, but not past, its base you wind up with, in effect, a "seat" of brass all the way around the base of the bullet past which the bullet can't be driven. This, combined with the fact that the bullet circumference (all the way around the sides of the bullet from the case mouth down) against the interior of the cartridge casing gives you one hell of a lot more surface-area-to-surface-area contact and friction than just the small area around the case mouth, prevents the bullet from setting back. Overcrimping to prevent bullet setback is a classic case of doing something that's not only not going to accomplish what's intended, it can actually cause the problem that's trying to be prevented. Overcrimping causes the area along the casing under the crimp to bell outward, destroying casing-to-bullet friction along a huge length of what would otherwise be secure contact area. IOW overcrimping can cause bullet setback, not prevent it.

[Flatland Shooter]

After reading about how much crimp some of my fellow shooters put on their loads, I noticed that no one has mentioned how excessive bullet pull , i.e. excessive crimp, will affect your load.

Shooting 9 Minor probably no problem. You have a little room for comfort.

But if you are shooting 9 Major be warned that increasing the bullet pull (crimp) will also increase the load's pressure.

The tech folks at Dillon are more than willing to discuss just how you set up your loads and several times through the years I've had them offer that cautionary note.

Bill

[High Lord Gomer]

*NOW* I'm thoroughly confused!

2 Questions:

1. Is there any reason to ever crimp (more than just removing whatever bell you may have made)?

2. What about .357 Sig where there is very little case contacting the bullet?

[G-ManBart]

After reading about how much crimp some of my fellow shooters put on their loads, I noticed that no one has mentioned how excessive bullet pull , i.e. excessive crimp, will affect your load.

Shooting 9 Minor probably no problem. You have a little room for comfort.

But if you are shooting 9 Major be warned that increasing the bullet pull (crimp) will also increase the load's pressure.

The tech folks at Dillon are more than willing to discuss just how you set up your loads and several times through the years I've had them offer that cautionary note.

Bill

Crimp and bullet pull aren't synonymous.....neck tension and bullet pull are. Crimp is a measurement that doesn't correlate directly to neck tension.

I certainly don't discount what the folks at Dillon would have to say, but I don't believe too much neck tension causes an unreasonable increase in pressure. I also don't know how it would even be possible to get too much neck tension short of very thick brass, and undersized resizing die and an oversized bullet. Most 9 Major loads are coke-bottle shaped to start with....that's as much neck tension as possible....and they're not experiencing problems because of it. R,

[Flatland Shooter]

Most 9 Major loads are coke-bottle shaped to start with....that's as much neck tension as possible....and they're not experiencing problems because of it. R,

Interesting comment "most 9 Major loads are coke-bottle shaped to start with.".

We have a few 9 Major shooters down here but I've not seen any with the coke-bottle shaped loads. I'm not saying there is anything wrong with loads like these, but are they all that common? I've always tried to keep my reloads as close to factory dimensions as possible but if folks are having good performance with this much neck tension, I might like to give it a try.

Bill

[GrumpyOne]

The "coke bottle effect" is caused by the sizing dies. I haven't really noticed it in 9mm, but in 40 S&W it is quite noticeable. Using a 550 with the Dillon 40 S&W dies, you don't really see it until the bullet is seated. I know there are a few pics somewhere here in the forums depicting it. Do a search for "coke bottle" and the posts should come up.

[G-ManBart]

Most 9 Major loads are coke-bottle shaped to start with....that's as much neck tension as possible....and they're not experiencing problems because of it. R,

Interesting comment "most 9 Major loads are coke-bottle shaped to start with.".

We have a few 9 Major shooters down here but I've not seen any with the coke-bottle shaped loads. I'm not saying there is anything wrong with loads like these, but are they all that common? I've always tried to keep my reloads as close to factory dimensions as possible but if folks are having good performance with this much neck tension, I might like to give it a try.

Bill

I've seen quite a few shaped that way. I don't load Major 9 now, but my Minor loads using a standard Lee resizing die, Lee expander/powder funnel die, Redding Comp Seating Die and Hornady Taper crimp dies show a slight coke-bottle shape. It's not dramatic, but it's there. I've taken seated bullets and pushed them against the edge of the loading bench as hard as I can and gotten zero setback according to the dial calipers. I haven't tried it, but I should try feeding a couple of dummy rounds that are with a bullet seated, no crimp and see if that will cause any setback (just for info sake). R,

[Flatland Shooter]

I've seen quite a few shaped that way. I don't load Major 9 now, but my Minor loads using a standard Lee resizing die, Lee expander/powder funnel die, Redding Comp Seating Die and Hornady Taper crimp dies show a slight coke-bottle shape. It's not dramatic, but it's there. I've taken seated bullets and pushed them against the edge of the loading bench as hard as I can and gotten zero setback according to the dial calipers. I haven't tried it, but I should try feeding a couple of dummy rounds that are with a bullet seated, no crimp and see if that will cause any setback (just for info sake). R,

Went out to the reloading bench and screwed down the Dillon taper crimp die about a quarter turn. The result is a loaded round that follows the contour of the bullet, then at the base of the bullet tapers in slightly and as we continue down to the extractor groove it returns to full diameter. This is the "coke-bottle" shape, right?

Now I'm thinking of a way to measure how much weight on the end of the bullet is required to cause the bullet to set back. Compare that to my "standard" load and possibly against a factory WW White Box load to see how much difference there is.

Trying to determine how much pull is needed to pull the bullet from each of the three cases might be a little more difficult but if it turns out the pull is significantly increased, pressure might also be increased. If pulling bullets from each of the three cases is about the same, then there is no reason to think that extreme crimp would cause extreme pressure.

Thanks for the info.

Bill

[G-ManBart]

Yep, that's the shape I was thinking about.

I'd be interested to hear what you come up with on the amount it takes to cause setback. Maybe an arbor press with a FT/LB gauge? R,

[Duane Thomas]

I understand the need to test things instead of taking another person's word for it. I'm that way, myself. Just call me Doubting Thomas. Having said that, this is an awful lot of work being expended toward "figuring out" something that really was figured out decades ago.

[1SOW]

Shooting 9mm jacketed bullets-minor PF: Everything I've read in manuals and various reloading articles has led me to 'crimp' to remove the case mouth bell made by the powder die. I honestly don't remember where, but I also read that this should not deform the bullet in any way.

I use Lee dies and they do leave the slight coke-bottle shape.

I also sort bullets. (2 X case thickness) + bullet diameter should be the measurement at at the case mouth of the loaded round.

My digital vernier isn't accurate to that degree. My win cases end up around .377/+ and pulled bullets have no indented marks or lines .