help me understand crimping

O

Ocraknife

New member
Right now I'm only loading for two chamberings, 9mm and 41 mag. Would someone help me understand crimping, the whens, hows and whys?

My die sets didn't come with crimping dies but I'm not sure if that means anything or not other than they want to get as much money from me as they can.

I've read that I don't need to crimp 9mm provided it fits in the chamber of the gun I'm using. I don't know if this is true or not.

I've also read that all revolver rounds need to be crimped but I don't know if this is true or not because I've read material that seems to make the issue of crimping seem ambiguous.

Any thoughts?
 
Your die sets may not have separate crimping dies, but but the seating dies incorporate the function. Automatics like the 9 mm typically use a taper crimp. That just takes the flare out of the case. Revolvers, especially magnum rounds like your. 41, use a roll crimp. That crimp is essential to proper function. Study your loading manual for details.
 
I feel your pain.

When I started my manual made no mention of crimp and the only reason I knew was down to the die set-up instructions.

The next massively grey area is how much. That too was a mystery with posts talking about too much or not enough but never saying what the meant,

Here's my limited knowledge:

Crimp revolver rounds so that they don't jump under recoil nd eventually come so far out that they stop the cylinder rotating. The most I've ever used is a half turn on some heavy mag loads using a LEE FCD

Crimp semi-auto pistol rounds so as to remove the flare from the bullet seating phase and aid feeding.

Don't bother crimping rifle cartridges as the neck tension should be enough.

Consider crimping a little if you have unburnt powder: it may be because the pressure was not able to build enough to give a decent burn.

Now I'll just sit back and wait for more experienced reloaders to pull my advice apart! :D
 
Your die sets may not have separate crimping dies, but but the seating dies incorporate the function. Automatics like the 9 mm typically use a taper crimp. That just takes the flare out of the case. Revolvers, especially magnum rounds like your. 41, use a roll crimp. That crimp is essential to proper function. Study your loading manual for details.
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Thanks. I have Lyman's 3rd Edition "Pistol and Revolver handbook" and Hornady's 9th Edition "Handbook of Cartridge Reloading". Neither are offering a lot of information on crimping but they have enough to make me realize that I need more information before proceeding, which is good.
 
I feel your pain.

When I started my manual made no mention of crimp and the only reason I knew was down to the die set-up instructions.

The next massively grey area is how much. That too was a mystery with posts talking about too much or not enough but never saying what the meant,

Here's my limited knowledge:

Crimp revolver rounds so that they don't jump under recoil nd eventually come so far out that they stop the cylinder rotating. The most I've ever used is a half turn on some heavy mag loads using a LEE FCD

Crimp semi-auto pistol rounds so as to remove the flare from the bullet seating phase and aid feeding.

Don't bother crimping rifle cartridges as the neck tension should be enough.

Consider crimping a little if you have unburnt powder: it may be because the pressure was not able to build enough to give a decent burn.

Now I'll just sit back and wait for more experienced reloaders to pull my advice apart!
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Will the crimp that happens with the bullet seating die suffice?
 
Cast bullets for the. 41 mag will have a crimp groove (the topmost groove) and jacketed bullets will have a cannelure for crimping. As pointed out above, your seating die also doubles for applying a roll crimp into the crimp groove for a cast bullet or the cannelure for a jacketed bullet. Remove the seating stem from the die and a shoulder will be observed some distance into the die. The shoulder is what applies the roll crimp. First adjust the bullet seating depth to the point where the case rim is adjacent to the crimp groove or cannelure. Then back off the seating stem and gradually turn down the die body until a proper crimp is applied. Now screw the seating stem back down to again contact the bullet and now seating and crimping should about be coordinated. Some final small adjustment may still be needed.
 
Cast bullets for the. 41 mag will have a crimp groove (the topmost groove) and jacketed bullets will have a cannelure for crimping. As pointed out above, your seating die also doubles for applying a roll crimp into the crimp groove for a cast bullet or the cannelure for a jacketed bullet. Remove the seating stem from the die and a shoulder will be observed some distance into the die. The shoulder is what applies the roll crimp. First adjust the bullet seating depth to the point where the case rim is adjacent to the crimp groove or cannelure. Then back off the seating stem and gradually turn down the die body until a proper crimp is applied. Now screw the seating stem back down to again contact the bullet and now seating and crimping should about be coordinated. Some final small adjustment may still be needed.
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Thank you. So, it sounds like I don't need any extra equipment then? I was just about to order a factory crimp die so I am glad I read this.
 
You're good to go; no additional crimping die needed. That combination seating/crimping die is common for many handgun and rifle calibers. The 9mm utilizes a taper crimp that can also be in combination with the seating die or can be separate.
 
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Crimp revolver rounds so that they don't jump under recoil nd eventually come so far out that they stop the cylinder rotating. The most I've ever used is a half turn on some heavy mag loads using a LEE FCD
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But James,the FCD does not roll crimp the bullet seater does that.
 
There's a lot to the crimping subject but none of it gets overly complicated, IMO. The biggest thing to know is that semi-auto ammo usually headspaces on the case mouth so the loading dies apply a taper crimp.

Me, I wish our handloading forefathers had named it something OTHER than "crimp." Because for semi-auto rounds, the taper crimp pretty much simply "fixes" the case mouth flare from an earlier handloading step. If you take nothing else from this subject, know this: semi-auto taper crimp DOES NOT HOLD THE BULLET in place in your brass. Case mouth tension is established with proper sizing and -not- taper crimping.

In revolver ammo like your .41 Mag, your bullet seater die can impart a roll crimp. And this type of crimp absolutely does help to grip and hold the bullet in place. For a heavy recoiling revolver round, a solid roll crimp keeps your bullets from jumping forward under recoil. And in a magnum revolver round, a firm roll crimp absolutely helps a slow burning powder to get a solid starting burn before the bullet starts to move.
 
Thanks for asking our advice.

polyphemus said:
But James,the FCD does not roll crimp the bullet seater does that.
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I beg your pardon, polyphemus, the FCD for revolver cartridges does perform a roll crimp. The FCD for straight-walled semi-auto pistol cartridges performs a taper crimp and the FCD for gottlnecked cartridges os completely different in design and function than the FCD for straight-walled (and taperd like the 9mm) cartridges.

Semi-auto straight-walled cases must not be roll-crimped because the case mouth must rest against (this is called "headspace" or "Headspacing"). Rolling it iin would compromise headspacing.

Most of the retention of the bullet in the case is typically provided by friction of the case wall against the sides of the bullet. Rolling in a case mouth (for revolver cartridges) can sometimes loosen that friction. Die adjustment is a fine art. Rolling a case mouth into a crimping groove also "works" the bras more, shortening the brass' life. Case cracks at the mouth show up eventually unless you anneal the brass. Pistol brass is cheap enough that most reloaders don't bother.

Lead bullets take a bit of a different approach than jacketed bullets, too. Friction of brass on copper is a little different than brass on lubricated lead and the FCD tosses in another issue - post-sizing. The Lee FCD has a sizing ring at its base which sizes the loaded round down as the cartridge is withdrawn from the FCD (to ensure easy feeding into the chamber), but brass springs back a bit more than lead. This loosens the grip of the brass on the (lead) bullet, too. Some people knock the post-sizing out of the die to cure this "problem" Some don't see it as a problem.

If you get bullet creep in a revolver, before you apply more crimp, inspect loaded rounds to make sure you have not compromised the friction grip with too much roll crimp before you go making it worse. However, having said that, Sevens is spot-on that roll crimp does provide a very important assist to firction keeping that bullet in place under recoil and for getting a slow-burning powder up to its proper performance (pressure) range.

Note: Slow powders get the maximum energy out of any given cartridge. Fast powders cannot get up to the energy levels of a slow powder. They run out of pressure too fast and adding more of a fast powder spikes the initial pressure too fast. In short: Fast powders are fine for light-to-medium loads. But it takes the long burn of a slow powder to get maximum performance. But yoiu have to keep that bullet in place a bit longer (bullet retention) to get that slow powder into its favored performance envelope.

Good Luck.

Lost Sheep
 
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I'd suggest something, but you're likely to have a lot of disagreement with me.

I would suggest that you buy a separate crimp die, or even try to find a separate seating/crimp die. It is best, imo, to crimp and seat in two steps.

Setting up a die to perform a crimp and seat at the same time, at least to me, is a huge pain, and I have always done it separately. I have several separate crimp dies. I would rather go through the extra process.

The inconsistent length or cases results in inconsistent crimps, and at times, literally crushing the case mouth as you try to push the die to the full lenght of bullet insertion. So, I tend to use four steps, seating the bullet properly and then crimping mostly by feel. The crimp dies are sort of self limiting.

Someone needs to explain what you are supposed to do with the revolber when your bullets don't have cannelures and you need to roll crimp.
 
I agree that seating and crimping separately, even with one die, is the way to go. Regards loading for revolvers with no groove or cannelure, just don't. One exception: Speer lists a load for .32 S&W Long using their 60 grain GDHP designed for .32 ACP. Need to have uniform case length and seat to a specific COL, then crimp over the ogive. It works, but mostly just leave those bullets to the bottom feeders.
 
crimping

Check UTube. Jiujitsu 2000 has 2 good videos on how to set up rifle dies and how to set up pistol dies.They are very informative.
 
the FCD for revolver cartridges does perform a roll crimp.
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ok,not long ago I was reading Richard Lee's book and right on page 55 he describes the seater die/roll crimp adjustment he makes no mention of doing that for the FCD.So I figured that roll crimping was done in the bullet seater die.I don't load revolver cartridges.
 
But James,the FCD does not roll crimp the bullet seater does that
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Pure horse poop. It surely does and as the internet goes more bad incorrect information being given out. You can even get a tapper crimp die for revolver rounds, from Lee. For me personally I use lee factory crimp dies on all my rounds which are 380acp, 9mm, 38spl, 357mag, 40S&W, and 45acp. Just like the lee web site and ALL there literature states using the Lee factory Crimp die YOU CANNOT OVER CRIMP A ROUND
 
Will the crimp that happens with the bullet seating die suffice?
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YES

When done "right". But doing it "right" takes a little bit of practice, and knowing what "right" is.

No, You do not need any additional dies. You may, decide you want a separate crimp die, but you do not NEED one.

What brand(s) of dies do you have, and how old are they??

I've been loading (and crimping) ammo in different ways for over 40 years. If there's a way to screw it up, I've probably done it, at least once. :D

Most of the important things about crimping have already been mentioned, so I'll try to hit points I don't think were, or were not mentioned, enough. ;)

9mm Luger and .41 Magnum, these are the two classic "taper vs. roll crimp" rounds (also tapered case vs. straight wall case). Seating dies have a crimping shoulder built in, the process for using it has been described, (and will be in the die instructions too, or SHOULD be).

In revolver rounds, the primary use is to prevent bullet jump during recoil. In magnum calibers, it also has the benefit of providing a bit more resistance to bullet movement allowing for the better combustion of very slow burning powders. In semi auto pistol rounds the crimp is to help hold the bullet in place during the stresses of the feeding cycle. In ALL rounds, the primary thing holding the bullet in place is case neck tension.

The important things are "enough" crimp to do the job, and in the right place. The die shoulder "rolls" (bends/folds) the case mouth into the bullet. There must be a space on the bullet for the case mouth to go into.

Meaning the case mouth must be aligned with the cannelure (crimp groove) of the bullet. IF not, crimping is a bad thing. If there is no groove for the case mouth to crimp into, the round can be deformed. Buckled brass, to the point the round will not chamber, is possible. The other possibility is (as was mentioned) the bullet being compressed, and the brass springing back, which can actually LOOSEN the hold on the bullet.

CASES MUST BE OF UNIFORM LENGTH, or you will have to adjust the die separately for each individual round.

Take a look at a factory round to get a good idea of what the proper crimp should look like.

TAPER crimp also presses the case mouth into to bullet, but uses a gradual taper, not a sharp shoulder like the roll crimp does. It also can be overdone, actually reducing the case grip on the bullet. Taper crimping does not require a crimp groove in the bullet, because the taper does not "turn" the case mouth into the bullet. Case length is still critical for uniformity, though.

I do not use the Lee FCD die, and have no opinion about it, other than I seem to be able to get along fine without one.

I do use a separate crimp die for some pistol calibers, as a convenience more than a need. Standard advice is to only use as much crimp (either type) as you need for reliable function.

Am happy to answer specific questions, just ask!:)
 
Thank you so much everyone. This has been very helpful.

My die for 9mm is Hornady American Series and for .41 mag it a Lee, three die set. Both are brand new.

On the 9mm I've flared the casings carefully, just enough to get the bullets seated without scraping the jacketing. Right now, there is only 2 one-thousandths of an inch in diameter between the case neck of the cartridges that I've made (but not yet crimped) and the factory rounds. In my test chamber - the barrel of an H&K VP9, both my rounds and the factory rounds appear to head space identically.

As for roll crimping the revolver bullets with cannelure, should I seat the bullet to the middle of the cannelure? What happens if this doesn't correspond to the stated COL or is that something that something that doesn't happen?

Thank you.
 
Ideally, at least for appearance, seat the bullet to the center of the cannelure but OK if OAL seems to be improved by offsetting slightly one way or the other.
 
In my experience crimping revolver ammo, I seat the bullet to the case mouth almost even with the top of the groove. But actually a few thousandths either was makes no difference as long as the case mouth has room to curl into the groove. For revolvers just seat bullet to crimp groove or cannalure and disregard book OAL. Rule of thumb; revolver bullets with cannalure of crimp groove get roll crimped. Semi-auto bullets sans cannalure and crimp groove gets a taper crimp (but I don't "crimp" semi-auto reloads, I just "deflare" with a taper crimp die). Smooth sided plated bullets toss a monkey wrench into the rule of thumb, but I treated them same as semi-auto bullets no matter what gun I shot them in, taper crimp...
 
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