9mm crimping curiosities

[jbauch357]

I pulled apart a couple of my 9mm rounds after becoming curious how much the bullets were being indented in the crimp die. When I pull the Rainier bullets that I’ve loaded they’re considerably collapsed (in my eyes), but when I pull a harder true jacketed factory loaded 9mm round there is little or no indentation on the bullet.

How much crimp should I be putting on these rounds with the softer bullets? My main concern is crimping too much and causing dangerous chamber pressures – but deforming the bullet and causing accuracy issues also comes to mind.

Load measurements:
9mm
Overall Length: 1.150”
Case diameter: 0.374”
Crimped case neck diameter: 0.372”
Bullet diameter: 0.353”
Minimum crimped bullet diameter: 0.345”

 

[rcmodel]

Taper crimp has little to nothing to do with raising chamber pressure. Unlike a roll crimp, it won't have a grip on the bullet much at all, no matter how much you crimp it.

You only want enough crimp to straighten out the case mouth bell and just barely kiss the bullet jacket.

Too much taper crimp can have the effect of loosening the jacket on a true jacketed bullet.

It squeezes the bullet under-size, the lead core stays squooze, and the harder jacket springs back away from it against the case crimp.

Use your loading manual SAAMI case spec drawing as a guide. Then measure the case after crimping. It should be no more then .001" or .002" less then the drawing dimension depending on case mouth thickness of the brass you are using.

rc

 

[Hk Dan]

It's common. Rainiers are plated, as you noted, and won't hold up as well as an FMJ if they're pulled. It's nothing to worry about, but don't reuse the bullet.

 

[jbauch357]

OK, as long as it's not a safety issue I'll probably leave it be for now and see how they shoot.

Being they're Rainier bullets I've also loaded to 10% under recommended load for the round - at 6 grains of Alliant Power Pistol.

Thanks for the help!

 

[Walkalong]

Here are some properly crimped .45 ACP's. 9MM is the same.

Pic 1

Pic 2

Pic 3

 

[jbauch357]

I'll take a picture of the pulled bullet tonight to show the indentation on the bullet itself...

Being the neck is only crimped to 0.002" smaller than the rest of the case I think I'm about right - but am amazed at how much it squishes the bullet...

 

[rcmodel]

If it squishes the bullet at all, it is too much.

rc

 

[D. Manley]

If it squishes the bullet at all, it is too much.

Exactly. Reduce the crimp until the plated bullets are no longer disfigured and you're good to go. The lesser setting will do just fine with true jacketed as well. IME, a slightly visible crimp ring does no harm but it should not resize/deform the bullet at all, should not be deep enough to feel and certainly not to cut into the plating. FWIW, I set all my crimp adjustments for pistol rounds with plated bullets and leave the setting "as is" for jacketed as well...never presented a problem in any respect.

 

[jbauch357]

well crap - anybody else care to ease my worries and confirm that the over-crimping won't result in catastrophic chamber pressure and a trip to the hospital?

 

[rcmodel]

I doubt that it is dangerous. At most, a plating separation and poor accuracy and/or barrel leading.

I have heard of the back half of the plating coming clear off in a revolver forcing cone and cuasing a bore obstruction when crimped like that.
Internet rumor? or not? it would ruin your day if it did happen.

But no worry there in a 9mm auto pistol.

rc

 

[jbauch357]

ok - over-crimping in itself not much of a danger, that's good...

the next possible "big problem" that somebody mentioned is that a 9mm round headspaces on the casing itself. so if I've buried the case too deep into the bullet, the case could possibly slip up into the chamber while loading - then when shot there wouldn't be enough room to expand and release the bullet causing that feared catastrophic failure...

in the end I'm probably just going to shoot them up and see what happens, smart eh

the only thing that makes me feel a little better about this is I'll be shooting in a .40 to 9mm conversion barrel that has a fully supported chamber and will be considerably more sturdy than my other factory 9mm barrels.

 

[rcmodel]

then when shot there wouldn't be enough room to expand and release the bullet causing that feared catastrophic failure

You are over-anal-izing this.

In the event the crimp allows the case to go too far into the chamber?
The extractor hook will stop it.

Then, the first thing that will happen when the primer pops is, the primer will back out to the breach face.
Then, the case, being much lighter then the bullet, will slam backward into the breach face and re-seat the primer, while the pressure builds and gets the bullet moving in the other direction.

Not to worry so much.

You aren't loading a MAX load, and have some wiggle room built in.

rc

 

[edSky]

I've been told by a master gunsmith and bullet caster that a 9mm crimp should be between 0.373” and 0.375". I don't think you need to worry. He even said if I don't see a slight ghost-ring from the crimp it's not crimped enough.

 

[rcmodel]

.373" to .375"??

Thats .005" to .007" below SAAMI spec for a 9mm.

I don't care who your ex-spurt is, he is wrong.

And especially wrong with the plated bullets the OP ask about.

rc

 

[jfdavis58]

I have a slightly different take on taper crimping.

First, straight-wall auto pistol cartridges headspace on the mouth of the case; the case mouth insures that the case head/primer are in firm contact with the breach face and within the reach of the firing pin. The crimp must NOT interfere with this requirement.

I use a tight maximum catridge gauge (LE Wilson, Dillon, Lee-any will do) and set the die to produce a straight wall from head to mouth. This is by feel--you can feel if the mouth is scrapping the gauge, you can feel when it is still belled out to accept a bullet.

The purpose of the crimp is to prevent bullet set back while the cartridge chambers-ONCE. From the straight walled position I make sets of ten empty rounds (no primer and powder); each with the die turned further down from the straight wall position by 15-30 degrees of rotation. With a set of ten I load a magazine, seat it in the gun and vigorously cycle the slide. I collect the cartridges and repeat-twice more. After the third run I collect and measure overall length. When all ten cycled three times exhibit no more than 0.001 or 0.002 inches of set-back, I stop; tighten the locking nut and proceed with reloading. I seldom need to dial in more than 60-75 degrees of turning on the die; there is little or no visible deformation of the case mouth. If you back-out all the other dies on a progressive press or use a single stage, you can just feel someting more than contact.

As stated the headspace issue is critical. Too much taper crimp will allow the cartridge to fall/push past the ledge from chamber into the leade/throat of the barrel and this could cause a light primer strike, a hang fire or other problems like a jammed, live cartridge in the barrel.

There are real problems with using exact measurements as found in manuals and cartridge diagrams. Die makers tend to produce dies that resize to the minimum case/cartridge diameter. Gun makers tend to produce chambers that are towards the maximum cartridge diameter in mass market firearms. God ONLY knows to what diameter some bullets are actually swaged. Case wall thickness varies from maker to maker, even within one maker on different lots. A 0.001 to 0.002 crimp may not catch and headspace properly; in all likelihood using the absolute minimum diameter as a crimp setting as suggested by some respondents guarantees a failure in some guns. It is also difficult (maybe impossible) to get an accurate placement of the caliper measurement surfaces directly on the edge of the tapered (angled) case mouth, squarely to the surface of the case head.

During die adjustments you should remove your firearm's barrel and carefully slide each round into the chamber to see that it seats properly with mouth on the ledge. Discard/disassemble any that fail to catch. You should consider a cartridge gauge. You will need to do some of this 'by feel'.

 

[Walkalong]

That is the long version of what we have said. Just enough crimp to remove the bell, and maybe a hair more. Hopefully you have helped the OP understand and quit worrying.

 

[D. Manley]

.373" to .375"??

Thats .005" to .007" below SAAMI spec for a 9mm.

I don't care who your ex-spurt is, he is wrong.

And especially wrong with the plated bullets the OP ask about.

Right again. Even with the thinnest brass, anything below .375 is over-doing it and in most headstamps, .376 to .377 should be near perfect.

To the OP, none of this means much as far as a "hazard" goes provided it's not to the extent you actually compress the bullet sufficient to reduce the case tension actually holding the bullet. Plated bullets are, by the nature of their construction, soft. The greater risk (if you call it that) in deforming them by over-crimping is that it can ruin accuracy potential.

 

[jbauch357]

Thanks all very much for the good info! Obviously I needed to slow down more in the reloading process rather than just cranking a bunch of these out.

Here is a pic of what I have now, depending on how I feel about it after pondering some more I may pull everything apart and start from scratch.

 

[jbauch357]

Never mind, about 1 in 5 I can get to push past the chamber and get stuck on the case - they're all coming apart and I'm going to start from scratch (removing the primer punch though so I can still re-size and not deal with de-priming live primers).

How bad of an idea would it be to try and re-use the bullets?

 

[D. Manley]

Way too much crimp. I'd shoot the ones loaded "as is"...you will gain nothing by pulling them and reloading and could easily make any problems worse.

Back off the crimp and re-set it again from scratch using new bullets...seat, measure and pull the bullets. As you get to around .377 go very slowly and check the bullets. You should get to the point you have a perfectly acceptable crimp that no longer mars the bullets...this will most likely be .3765/.3775 measured at the case mouth.

 

[Walkalong]

Ditto what D. Manley said.

My crimp is so light I have to use magnification to see it. See pics 1, 2, & 3 again.

 

[jbauch357]

Re-adjusted and we're all good now. I can see the ring on the bullet from the crimp - but it's less than 0.001".

 

[D. Manley]

Sounds good. I occasionally have seen a slightly visible line on mine with no ill effects and when things are just right, most bullets will not even show that much. The difference is probably just a little variation in brass thickness, no big deal. Go light 'em...

 

[Ghiller]

9mm Crimp.

Everyone here seems to be correct, But here is a fool proof way to crimp...Set your die to loosely "grab" the bullet...Take the loaded round, and push the bullet head into your reloading bench, if it gets pushed into the case, then you have the chance of it pushing back when it is being slammed forward.
Tighten your crimp until it is too hard to push the bullet into the case...then, if you'd like pull one apart, and see what it looks like..Plated bullets will leave a crimp mark, and Jacketed most likely will not...If you can make a mark on the bullet with your fingernail, then it is probably plated, not jacketed.

 

[D. Manley]

Everyone here seems to be correct, But here is a fool proof way to crimp...Set your die to loosely "grab" the bullet...Take the loaded round, and push the bullet head into your reloading bench, if it gets pushed into the case, then you have the chance of it pushing back when it is being slammed forward.
Tighten your crimp until it is too hard to push the bullet into the case...then, if you'd like pull one apart, and see what it looks like..Plated bullets will leave a crimp mark, and Jacketed most likely will not...If you can make a mark on the bullet with your fingernail, then it is probably plated, not jacketed.

Not to be argumentative but, I have to disagree. Taper crimping cannot increase case tension on a bullet. This is a function of the resizing die and the "crimping" function merely serves to remove any belling of the case mouth plus, a fraction. Over-crimping can actually loosen the case's tension on the bullet. This is because when compressed, brass has the ability to "spring back" to some extent whereas, a lead, plated or jacketed bullet does not thereby, loosening the hold on the seated bullet. IMO, if a sized case fails to provide sufficient tension to hold the bullet then, there's another problem.