Let's talk about crimping the autoloader 9mm

Hmm. I used to crimp my 9mm, but have since stopped. I have found that neck tension keeps the bullet in the case without issue. I still have my FCD, but do not use it at present, nor do I crimp with the seating die. So long as the cartridge still chambers correctly, I do not see an issue with a light crimp, but have not found it necessary. YMMV.

I taper crimp and plunk test all 9 mm, .40 S&W, and soon to be .45 auto. Just makes sense to me.

Have a blessed day,

Leon

Neck tension and crimp are two different things. I load plated bullets so they don’t get swaged by the case (no ring around the bullet if you pull from case after being crimped).

For description purposes, you could call my “crimp” a “restore the case mouth to original dimensions, removing the bell or flair after the bullet is seated” step. the tension of the case is what is holding the bullet in place.

If you don’t have enough you might not be sizing the case enough, 9mm is tapered or you are expanding the case too much.

Main problem with thinking a heavy crimp helps hold a non cannelured bullet in place is that you squeeze the lead to a smaller dimension and it stays there, while he brass “springs” back some amount, usually exacerbating the problem.

Measuring crimp is actually not that easy to do in a repeatable, meaningful way for many of us. I have never bothered with trying to quantify/measure it. Here's what I do.

Get a case gauge or, if you have only one gun you're loading for, pull the barrel. Back out the crimp adjuster (the knob on top of the FCD). Put in a loaded, but as-yet-uncrimped round. Raise the press. Screw down the adjuster until you get resistance. Lower the ram a bit and turn the adjuster down a bit (maybe a quarter of a turn). Take the round off the press, see if it fits freely into the case gauge/barrel and can spin freely in same. If not, put it back on the press, turn the knob a bit more, and repeat. Keep going until you get to the point where it plunks freely. Now run another un-crimped round through and make sure you get the same result (sometimes a round that is being "crept up" will react differently than one handled in one pass, so you want to address that variable).

Now you are at the bare minimum of required crimp for that set of components. I usually dial in just a touch extra so that an extra thick case or the like doesn't cause problems. How much will this measure with calipers? I have no earthly idea.

I'll add one more variable. Different case lengths. If you use range pick-ups you can have a good mix of case lengths and it will be hard to set a crimp amount that is precise. I just try to find a middle of the road amount and also use the Lee fcd as added insurance. I believe case tension does the majority of the work though.

The Lee FCD is a collet-type crimp so case length should not have much effect on amount of crimp.
I use mine to remove the case flare and just a touch more for consistent feeding.

egd said:

I just try to find a middle of the road amount and also use the Lee fcd as added insurance.

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Do you mean that you crimp while seating and then separately run through the FCD?

preacherJohn said:

LNL AP ... 9mm Lee factory crimp die ... plated 115gr JHP’s from Ranier

When I released the slide, the bullet jammed on the feed ramp, and after I cleared it, I noticed the bullet was seated considerably lower in the case than what I set it at ... I realized the crimp was too light ... I'll need to reset that crimp.

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With straight walled semi-auto cases and taper crimp, it's not the crimp that holds the bullet but the neck tension from resizing the brass. If you experience significant bullet setback, it's not from insufficient taper crimp rather insufficient neck tension.

Make sure you are full-length resizing your brass. With all stations full and ram lever all the way down, check to see if you see daylight between bottom of resizing die and top of shell plate. If you do, you may not be resizing the case neck enough. I use Lee dies and adjust my resizing die so it barely kisses the top of the shell plate and I do not see daylight. Even with mixed range brass that vary in case length and various 100/115/124/147 gr bullets using different OALs, I essentially do not experience bullet setback when they are chambered from the magazine.

preacherJohn said:

So, how much crimp are you using on your medium size 9mm loads, say around 1050-1100fps? And again, this is with the plated bullets.

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Powder charge range does not determine the amount of taper crimp rather the diameter of the bullets. Since case wall thickness averages around .011", I usually add .022" to the diameter of the bullet to determine the amount of taper crimp. I found adding .022" to the diameter of the bullet, I return the flared case mouth back flat against the bullet.

So for .355" sized bullets, I use .377" taper crimp. For .356" sized bullets, .378" taper crimp. Taper crimp amount does not change whether I am loading light target loads or full-power duplicate factory JHP practice rounds. And yes, jacketed bullets do come in different sizes - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10567453

If you have any concerns about accuracy/wear of your calipers, $5 pin gages allow verification - https://www.zoro.com/vermont-gage-plug-gage-minus-0355-in-black-911235500/i/G0146955/

Also, what brass did the setback occur in/with? If I want to generate setback (joke - I don't ever want setback!) there are certain brands of brass in certain calibers that will give it to me very reliably, regardless of what I do with dies or crimp.

drband said:

The Lee FCD is a collet-type crimp so case length should not have much effect on amount of crimp.
I use mine to remove the case flare and just a touch more for consistent feeding.

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I generally do not use a fcd but when I do this ^^^ is how I use it. In the 4 die Lee set, die #3 (seat/crimp die) I back off the body threads a few turns and use the seating stem to seat the bullets where I want them. That die will then not touch the case mouth flair. The use the fcd as a taper crimp die to just remove the flair. I use a case gage to verify and pull the first bullet to check for excessive crimp.

Walkalong said:

Neck tension holds the bullet.

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^^^ Very true

drband said:

The Lee FCD is a collet-type crimp so case length should not have much effect on amount of crimp.
I use mine to remove the case flare and just a touch more for consistent feeding.

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One problem when talking about Lee FCDs is that there is two distinct, different type of FCDs and they are often mixed up. One is for handgun cartridges. IMO a tool of little or no value. It is and adjustable crimp sleeve with a carbide sizing ring. The second is an FCD for rifle cartridges. IMO a good designed collet crimp die.

I don't "crimp" my semi-auto ammo in the normal sense. I just use a taper crimp die to remove flare in the mouth and insure good feeding/chambering. I use just enough to pass the plunk test.

If my gun misfed for any reason, I'd fix that first rather than change my ammo to work in a malfunction...

“I generally do not use a fcd but when I do this ^^^ is how I use it. In the 4 die Lee set, die #3 (seat/crimp die) I back off the body threads a few turns and use the seating stem to seat the bullets where I want them. That die will then not touch the case mouth flair. The use the fcd as a taper crimp die to just remove the flair. I use a case gage to verify and pull the first bullet to check forexcessive crimp.”

^^^^^
Exactly!

Properly adjusted, a pistol Lee FCD works great for removing flare. That's how I use mine. I prefer not to have to juggle two variables with a single die, and I load on a turret or progressive, so crimping separately is no extra work.


If I loaded on a single stage press, I'd probably just work hard to make the seating/crimp combo work well.

I am with those who don't crimp at all or just do enough of a taper crimp to remove flare. I also barely flare my cases when using jacketed bullets. I flare just enough that the bullet will sit on top of the case and, with very light pushing down, will stay upright without tipping over.

Lead projectiles are another matter.

Lee rimmed caliber (38, 357, 44 etc...) FCDs produce a standard roll crimp. They do have a carbide sizing ring but it seems very generous in size. I hardly ever feel it in use.

Lee auto pistol cartridge dies (380, 9mm, 40, 45, etc...) impart a taper crimp, though they, too have a carbide sizing ring. Easy to control taper crimp.

Rifle dies are as you noted.

Some folks knock out the carbide rings from the FCDs but I find that unnecessary.

Let’s not get into a FCD die bashing. Some of us use them, some do not.

preacherJohn said:

I set my factory crimp die like Lee said to do; off the top of my head without looking at the paper it was like - screw die down till it touches the case, lower ram, then turn clockwise 1/3-1/2 turn for a light crimp.

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When dealing with a FCD, this is a reliable way to talk about the degree of crimp. Lee recommends a half-turn for a light crimp or a turn for a heavy one. I prefer to crimp my 9mm and with heavy-plated bullets generally use 3/8's of turn, a little less for those with thin plating. I also resize the cases as BDS described and prefer for them to exhibit a bit of the 'coke bottle' profile once the bullet is seated.

On any cartridge that headspaces on the mouth, I apply just enough of a taper crimp to remove the belling of the case mouth. Nothing more.

PreacherJohn wrote:
When I released the slide, the bullet jammed on the feed ramp, and after I cleared it, I noticed the bullet was seated considerably lower in the case than what I set it at. Hmmm, right then I realized the crimp was too light.

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I expect the neck tension of my reloaded cartridges to be sufficient to resist bullet set-back attributable to the dynamic forces of the gun firing repeatedly. I do not expect neck tension (or neck tension + crimp) to be sufficient to prevent the bullet moving when hammered by the pistol's slide or the rifle's bolt. I would assume the bullet had been pushed back into the case and segregate such a round for later inspection.

ATLDave said:

If I loaded on a single stage press, I'd probably just work hard to make the seating/crimp combo work well.

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Without uniform brass this is an exercise in frustration! I load everything (at times 3k/year) on my Rock Chucker and finally broke down when MidWay put the small Lee Breech Lock press on sale for something like $27 which I use for crimping. I buy lock rings for all of my dies and also crimp just enough to remove any bell.

preacherJohn said:

I never really gave any thought to the case wall size before, and pretty much took for granted the bullet size was .355. I guess I've been doing this wrong for some time now. You guys raise a lot of different points I never considered. Guess I should have been on this forum years ago. So what happens when they produce the +P rounds? Do they set the bullet deeper, or tighten up the crimp? Both? or none?

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From the ammunition I've inspected it doesn't look like being +P changes much. You are only talking about 10% more case pressure in 9mm. Most factory ammunition will have a more pronounced crimp on it than what is recommended here, +P or not.

ATLDave said:

Do you mean that you crimp while seating and then separately run through the FCD?

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No, I said it wrong. I just use the fcd.
When I bought my LNL I bought it with the seat and crimp die, and was planning to use my fcd also as a finishing touch just to be sure things were good. But I'm too stupid to get the seat and crimp die set up together properly, so I backed off the crimp part and just use it as a seat die.