9X19mm Crimp Die vs. 9X19mm (combination) Seater/Crimp Die - Thoughts?

[Bret]

This might be a transfer/relic from reloading for revolvers, which is a different ball of wax, and in which a "heavy" crimp IS used to retain bullets...

I think that's exactly where the confusion comes from. The term taper crimp is a misnomer. It's not really a crimp. It's just debelling.

[chadbag]

I genuinely am curious what you mean by lightly taper crimping. I've heard that and heavy taper crimp and am at a loss to understand what is meant by either. The point of taper crimping is to remove the remaining flare from the belling step. The point isn't to help hold the bullet. When I setup a taper crimp die, I turn it down enough to completely remove the remaining flare, but no more. Anything more and I'd just be smashing the cartridge. So, there's nothing light or heavy about it. The die is just turned down far enough to do the job, no more and no less. I'm not saying that what you're doing is wrong or produces unsatisfactory results. I'm just curious what you mean.

Taper crimp is not just for "de-belling". Taper crimp is to adjust/increase the neck tension. LOTS of calibers that have no belling are "crimped" using a taper crimp. Look at all the rifle crimp dies that offer taper crimp. In most cases you are not belling those at all.

The taper crimp is used to do one or more of a few things -- increase the neck tension, even out or normalize the neck tension, "de-bell", etc. One reason to increase neck tension is for auto-loading rifles where you want to make sure the bullet does not get pushed in at all due to the action of loading (or firing for heavy recoiling calibers).

So adjusting your taper crimp die to touch your case and then turning it a fraction of a turn will apply a light crimp or "pushing in" of the brass to the bullet. This is most useful on those rifle rounds that have a cannelure, but even ones without a very light one will even out the neck tension or slightly increase it (you don't want to physically dig-in to the bullet obviously).

For rifle rounds shot from bolt or single shot guns this is less of an issue.

[Bimmer]

Taper crimp is not just for "de-belling". Taper crimp is to adjust/increase the neck tension. LOTS of calibers that have no belling are "crimped" using a taper crimp. Look at all the rifle crimp dies that offer taper crimp...

You're talking rifle rounds for semi-autos. We're talking pistol rounds.


AFAIK, for semi-auto pistol rounds, neck tension should be set by sizing the case, NEVER by crimping. The "crimp" really is just for "de-belling."


Again, revolvers and semi-auto rifles are different...

[chadbag]

You're talking rifle rounds for semi-autos. We're talking pistol rounds.


AFAIK, for semi-auto pistol rounds, neck tension should be set by sizing the case, NEVER by crimping. The "crimp" really is just for "de-belling."


Again, revolvers and semi-auto rifles are different...

If you want to limit it to pistol rounds, I would suggest that a light crimp for the purpose of making sure you have enough neck tension to keep the bullet from dislodging on loading is still a valid reason. I did a bunch of reading on this last night on the web and there is a variety of opinion. But a self-loading pistol can be quite violent on the round as it goes up into the chamber. I still set my 9mm and other similar rounds for the taper crimp die to touch the case and then lower the die a slight amount more. Not much but just a little. YMMV.

[Bimmer]

So adjusting your taper crimp die to touch your case and then turning it a fraction of a turn will apply a light crimp or "pushing in" of the brass to the bullet.

If you want to limit it to pistol rounds, I would suggest that a light crimp for the purpose of making sure you have enough neck tension to keep the bullet from dislodging on loading is still a valid reason. I did a bunch of reading on this last night on the web and there is a variety of opinion. But a self-loading pistol can be quite violent on the round as it goes up into the chamber. I still set my 9mm and other similar rounds for the taper crimp die to touch the case and then lower the die a slight amount more. Not much but just a little. YMMV.

"Touch the case and a bit more" seems really imprecise to me... I hate to be that kind of geek, but I adjust mine to make my rounds meet spec (measured with a calipers) and/or pass a "plonk" test.

And yes, semi-auto pistols are hard on rounds, and bullet set-back is potentially disastrous, but AFAIK the fix is proper neck tension by sizing in station #1, not crimping in station #4.

[chadbag]

"Touch the case and a bit more" seems really imprecise to me... I hate to be that kind of geek, but I adjust mine to make my rounds meet spec (measured with a calipers) and/or pass a "plonk" test.

And yes, semi-auto pistols are hard on rounds, and bullet set-back is potentially disastrous, but AFAIK the fix is proper neck tension by sizing in station #1, not crimping in station #4.

Didn't you screw up your neck tensioning with the belling action? You sized it (and got whatever your die gave you) at station 1. At station 2 (assuming a Dillon RL 550) you belled it a little. So you just messed up whatever station 1 did. Where else are you going to correct this?

[Bret]

Taper crimp is not just for "de-belling". Taper crimp is to adjust/increase the neck tension. LOTS of calibers that have no belling are "crimped" using a taper crimp. Look at all the rifle crimp dies that offer taper crimp. In most cases you are not belling those at all.

We have a fundamental disagreement here. Taper crimping for semiauto pistol cartridges is just for debelling. If you turn down the taper die more than necessary to just remove the bell, you're just smashing the cartridge. When removed from the die, the brass case will spring back more than the lead core bullet. As a result, case tension can actually be decreased by turning the taper crimp die down too much. Look at the inside of a taper crimp die. It's actually smooth. If you don't have enough tension between the bullet and case to prevent the bullet from setting back in the case, then something is wrong. Most likely the cases isn't sized enough (happened to me with a Hornady 40S&W die) or the bullet diameter isn't large enough (happened to me with some IMI 40S&W bullets) or a combination of the two. Fix the problem. Don't bypass it and try to resolve the problem by smashing the cartridge.

There are actually some 9mm bullets that have rebated bases, so it's not necessary to bell the cases. Zero Bullet Company makes a 147gr rebated base that's my favorite 9mm bullet. Because I don't have to bell the cases in order to start seating the bullet, I don't have to use a taper crimp die.


As for semiauto rifles, those are not taper crimp dies in spite of what the manufacturers might call them. Most are roll crimps which are the same as used on revolver cartridges and some are like the Lee Factory Crimp Dies for bottle necked rifle cartridges. Both types are designed to press the case mouth in to the bullet (cannelure typically) in order to help hold the bullet.

All that said, this is reloading theory. If what you're doing provides safe quality reloads, by all means continue to do what works for you.

[Bimmer]

Didn't you screw up your neck tensioning with the belling action? You sized it (and got whatever your die gave you) at station 1. At station 2 (assuming a Dillon RL 550) you belled it a little. So you just messed up whatever station 1 did. Where else are you going to correct this?

No...

Station one sizes down the top 2/3rds of the case.

Station two bells only the case mouth... Maybe the top 1mm or or 1/16" or so. (As little as necessary to enable seating without shaving the bullet.) The rest of the case, especially the sides of the case, stays sized.

Station three seats a bullet in the case, and the tension is the insides of the case on the cylindrical part of the bullet.

Station four merely de-bells the case mouth, and doesn't touch the lower part of the case.

[vicious_cb]

No...

Station one sizes down the top 2/3rds of the case.

Station two bells only the case mouth... Maybe the top 1mm or or 1/16" or so. (As little as necessary to enable seating without shaving the bullet.) The rest of the case, especially the sides of the case, stays sized.

Station three seats a bullet in the case, and the tension is the insides of the case on the cylindrical part of the bullet.

Station four merely de-bells the case mouth, and doesn't touch the lower part of the case.

?

Im not sure what dies you have in your station 3 & 4 but my stage 3 seats and removes the bell and my station 4 crimps the neck. This is a standard factory Dillion 4 die set.

[chadbag]

No...

Station one sizes down the top 2/3rds of the case.

Station two bells only the case mouth... Maybe the top 1mm or or 1/16" or so. (As little as necessary to enable seating without shaving the bullet.) The rest of the case, especially the sides of the case, stays sized.

Station three seats a bullet in the case, and the tension is the insides of the case on the cylindrical part of the bullet.

Station four merely de-bells the case mouth, and doesn't touch the lower part of the case.

This did not address what I said. The 9mm is not straight walled. It is a tapered case. When you bell it, you just messed up the neck tension at the point where you belled it (obviously not the rest of the case -- but remember this is tapered so the case mouth area is the most important).

I am bowing out of this. I am not an expert. I've loaded 9mm and 40 S&W for years applying a slight taper crimp (as I outlined before) and it has worked for me.

There is no way, without expensive equipment, for you to just de-bell using your die. You don't know exactly what the brass was sized to and the neck tension was before the belling to get back to it. Adjusting your crimp die to touch the case and then lowering the die another slight bit, maybe 1/8 turn, will lightly "taper crimp" it and provide a more uniform neck tension.

YMMV and all that.