9mm crimp for the 1000th time

[Six Shooter Steve]

Yeah I know this topic has been beat to death, but I cant find the info I need when I do a forum search. How much crimp do I actually need? I have seen in previous threads, people have said consult your reloading manual for crimp measurements, but mine shows none. So what should the top of the case measure compared to the base? That would show how much crimp is being applied corretct? Thanks guys

[Cloudpeak]

I taper crimp my 9's to .375".

I'm sure you know, but some reading this thread might not. In pistol cartridges that headspace on the case mouth, you use the taper crimp to remove the case mouth bell and you don't roll crimp as you do on revolvers. IMO, you derive little to no bullet holding capability from taper crimping. You taper crimp so the ammo will feed and chamber properly.

I always check for setback when first setting up. If there's a setback problem, it's caused by the sizer not sizing enough or the case mouth expander being to large of a diameter. I reduced the diameter on both my 9 and 45 expander's a bit until I had no setback after 6-8 loadings from slide lock with a dummy round.

[res45]

.375" is what I use,I took a few different factory rds. and measured them with my calipers it varied between .375 and .376" on steel and brass case ammo.

[grumpa72]

I read an interesting comment about crimping that got me to thinking, which is always a dangerous thing.

The writer commented that too much crimp actually compresses, or reduces, the diameter of the lead bullet. The brass, being more ductile, springs back into shape whereas the lead bullet will remain compressed. In this scenario, your crimp actually removes the gripping power of the case on the lead bullet. His comment was to crimp only enough to remove the belling and let the case do the holding on the bullet. The Lee instructions for their factory crimp die give very little direction on how much crimp should be used.

Comments on my post? I am curious from the more experienced reloaders.

[IllinoisCoyoteHunter]

Taper crimps are not really meant to grip the bullet. They are used to iron out the flare that you put on to accept the bullet. This is why it is important to not flare excessively. As stated above by grumpa, under an excessive taper crimp, the bullet will swage and the brass will spring back a bit. When setting up my dies, I always make a dummy round and run it thru my pistol a couple times....measuring COL to make sure there is no bullet setback. Good luck.

[Sevens]

Recognize that when talking about a semi-auto rounds the headspaces on the case mouth that CRIMP is not the way to keep the bullet in place.

Case mouth tension keeps the bullet in place. Crimp, in 9mm at the load bench, is merely a way to repair the belling you did to the brass when you flared it to accept a bullet.

First step-- don't flare the case mouth any more than you need to. It shouldn't look like the bottom of the liberty bell. Just a slight flare will prepare the brass to accept a jacketed bullet. A little more flare is necessary to accept a cast lead bullet.

Next, use a little crimp-- enough so that your loaded round falls easily IN to the chamber of your pistol, and drops easily OUT of the chamber of your pistol.

Do that and don't consider using any "crimp" to hold the bullet in place in 9mm. That's not the purpose of it.

Everything I just said is basically the same thing Cloudpeak posted, I just put it in to different words.

Yank the barrel from your 9mm pistol and use it to help you build functional rounds at the load bench.

[Six Shooter Steve]

Good deal guys, I am measuring .376 on the test rounds setting up my dies, so I should be in the good portion of the ballpark I did test it on one of my barrels, and cycled it through the gun a few times with no problems.

[res45]

That would be true with swaged or cast lead bullets which are typically .01 or .02 over bore dia. to much crimp will resize the bullet destroying the whole purpose of the bullet being over sized to the bore to begin with. So yes care should be taken not to overly crimp lead or plated bullets. .375 is what I use on regular jacketed bullets.

[Six Shooter Steve]

I am loading missouri cast lead bullets. They measure .356, is the .375 still an acceptable crimp measurement?

[Motownstan]

I am new to hand loading myself. I bought the 4 piece Lee die set. I don't even use the 4th (crimping) die. After seating the bullet the case mouth measures .376. I've fired about 100 of them in my Kahr K9 and CZ P-01 and they all work fine. I guess the crimping die is a waste of money?

[Lost Sheep]

Originally Posted by Six Shooter Steve

I am loading missouri cast lead bullets. They measure .356, is the .375 still an acceptable crimp measurement?

How thick is the brass at the case mouth? Never mind, this is better, below:

Do you have a bullet puller?

Load a round (no powder, though) just as you do all the others. Taper crimp as normal. Pull the bullet (or knock it out), being careful not to damage the side of the bullet.

What is the diameter of the bullet that was gripped by the case now? It is the same down at the base as higher up? Is it still .356?

If it's less than your groove diameter of your barrel, it is too small (you may get blow-by, which will contribute to barrel erosion and leading, as well).

You determine your groove diameter by pushing a slug through your barrel to force the slug to match your barrel dimensions, then measuring the slug. You also observe how hard it was to slug the bore. Variations in the force required mean your barrel is not the same dimensions throughout its entire length, which is generally a bad thing.

Any gunsmiths or experts on interior ballistics out there who detect something wrong in this post, please educate me (us).

By the way, you can now put powder and a bullet in the case you loaded for this exercise and use it as normal.

Good luck, always wear eye protection, especially when working with primers and don't pinch your fingers in your press.

Remember, only believe half of what you see and one quarter of what you hear. That goes double for what you get from the internet. Even this post. Maybe especially this post.

Do your own independent, confirming research when ANYONE gives you new facts on the web.

Also remember, even the idiotic stuff might have a kernel of truth buried in there somewhere.

Lost Sheep

disclaimer: I do not know you, so if my advice seems over-obvious, take into account my ignorance of your experience level. Also, other readers of all experience levels are reading.

[IllinoisCoyoteHunter]

No need to measure. That is not a good way to measure crimp due to bullet and brass variations in thicknesses. As stated before it is much easier to use your barrel as a gauge. The crimp does not hold the bullet in place, so no one can say for sure that .375 will work in your gun. You will need to lightly crimp some and see if they fall in and out of you barrell easily. Good luck!

[Lost Sheep]

Originally Posted by IllinoisCoyoteHunter

(edited for brevity and focus)
... so no one can say for sure that .375 will work in your gun. You will need to lightly crimp some and see if they fall in and out of you barrell easily. Good luck!

I can say for sure that .374" will work in your gun.

That is the standard diameter at the case mouth for 9mm parabellum (aka 9x19mm) The chamber inside dimensions are to let the cartridge fall into the chamber just the right distance (nominally 19mm, but my loading manual says 0.754") AND NO FURTHUR. There is a shoulder or step 19mm inside the chamber and that shoulder sharply steps the diameter of the chamber from chamber diameter down to bore diameter (EDIT: Originally, I used ".375" down to .355" ". Those are cartridge dimensions, not chamber dimensions. Sorry for the mistake and thanks to gregjc9 for spotting my blunder. I should have used SAAMI chamber dimensions, which I do not have handy, but that's what I meant). When the cartridge case falls just that far into the chamber, the case mouth is stopped by that shoulder and the primered end of the cartridge will be smack up against the breechface awaiting ignition. That is what the case mouth is for. To butt up against the shoulder so that the base of the cartridge will be up against the breechface and within reach of the firing pin. The case mouth (or the lip) is not meant to grip the bullet or to crimp into it.

The neck (not the mouth or lip) of the cartridge (the several millimeters BACK OF the very case mouth grips the bullet-with friction). The mouth-or the lip- is to butt up against that step, 19mm deep inside the chamber, which holds the cartridge firmly against the breech face. In a bottlenecked cartridge, the shoulder does that. In a blted case, the belt does that. In a rimmed case, the rim does that. In a rimless case (like the 9mm), the case mouth does that.

If the lips of the cartridge are crimped in more than .01" (.02" diameter reduction), the round will not headspace properly on the case mouth. It may still fire because of the extractor catching on the rim, but that is a lousy way to assure ignition in a firefight.

Anyhow, the advice to see if "they fall in and out of your barrel (the chamber) easily only tells half the story. The other half is where they should STOP. They should stop firmly and definitively against that step/shoulder in the chamber.

Sorry to be repetitive, but I want to be clear.

The lip of the cartridge case butts up against the shoulder in the chamber and keeps the cartridge positioned up against the breech face and firing pin.

For that reason, it has to be square and NOT crimped or rolled into the bullet cannelure or crimping groove.

The neck of the cartridge holds the bullet by friction. That is why the bullet is a press fit into the casing.

the 9x19 cartridge case has a slight taper to it and is nearly 10mm (.394") at the rim, .391" at the base and .374 at the mouth.

The mouth "steps" down in diameter to the bullet's diameter of .355" or .356". That step should be sharp and square, not in any way rounded (which a crimp would be).

Lost Sheep

[IllinoisCoyoteHunter]

To make things easier for you, I will use a diagram to help you along. This diagram was made by Unclenick and I take no credit for it. You say you are using lead bullets. For best accuracy and leading (if any leading), it is best to headspace the cartridge NOT off the case mouth, but off the bullet. It is important, as always, to start at the starting load and work up. The bullet will actually be in contact with the beginning od the rifling (the lands). I have found this method very beneficial in both 45 acp and 9mm. Check out post #38 on this thread http://thefiringline.com/forums/show...=324039&page=2 Good luck!

[CrustyFN]

No need to crimp 9mm. All you need to do is get rid of the flair the powder/expander die put in.

[Lost Sheep]

IllinoisCoyoteHunter posted a link to another thread wherein UncleNick posted (post #38, paragraphs 10 AND 11)

Originally Posted by UncleNick on post 38 of thefiringline.com/forums/showthread.php?t=324039&page=2

(edited for brevity and focus)...You need especially to ensure lead bullets are not pushed deeper into the case on loading or by the magazine housing recoiling against their noses. That is because lead bullets are lubricated and push in easily. You can often do that with your thumb if the case is not crimped.

The crimp fixes that. The standard taper crimp should dig into the lead bullet a little so it forms a step in the bullet that prevents it being pushed deeper in. Each time a case is reloaded, the brass work-hardens a little more. If it gets hard enough it will springs back enough after resizing to grip a bullet only weakly if at all. Remington .45 ACP cases are particularly famous for this.

Revolver shooters take great pains to crimp bullets (especially if shooting hard-recoiling rounds) so that the bullets do not come OUT of the cases. Semi-auto shooters should take care that the taper crimp "bites" into the bullet to ensure that the bullet does not get pushed deeper INTO the case.

I keep forgetting that (since I shoot mostly revolvers and rarely chamber any round more than once in my bottomfeeders). Also, I have never seen a more clear and succinct explanation of why.

Thanks, UncleNick and IllinoisCoyoteHunter.

Lost Sheep

[IllinoisCoyoteHunter]

I think that crimping the bullet with a slight "bite" or crimping to just iron out the flare will yield good results. I have done it both ways with great results. I prefer to just iron out the flare. But, I make sure to test a dummy round when I initially set up my dies. I chamber that dummy round and make sure there is no setback.