Measuring crimp on a 45acp

[Bugs100]

I was reading on one of the 1911 forums a discussion on measuring crimping on a 45acp.

It got me completlly confused. Some guys said measure a 1/16 of a inch below the edge of the case where it was belled and some guys said measure at the edge of the cartridge where the shell was belled. Which is where I haved always measured.

Which one is right?

 

[TY43215]

I can only answer this way, if you crimp too much, the case will bulge and the moon clip will not properly seat. I measure crimp at the edge and use a very light crimp.

Regards,

 

[Bugs100]

Is there a difference in where you measure from Taper crimping for Semi's to roll crimping for revolvers?

 

[Lugnut]

Bugs I crimp my .45ACP with a light taper crimp. Not even sure what the measurement is now. I measure right at the lip near the edge (I compared them to commercial ammo rounds). What matters most IMO is that the crimp allows no edge to cause jams AND the crimp only makes a light mark on the bullet (use an inertia puller and check bullet). My plated bullets only have slight marks.

 

[adweisbe]

I don't measure crimp at all. I back out the die so that zero crimp is applied and then turn it in until the flare from the case mouth is removed. If further crimp is necessary to get the cartridge to feed/chamber then something is wrong with the brass or bullet or the combination of the two. The crimp die is not there to swage an oversized bullet/brass combo.

 

[EddieCoyle]

I don't measure crimp at all. I back out the die so that zero crimp is applied and then turn it in until the flare from the case mouth is removed. If further crimp is necessary to get the cartridge to feed/chamber then something is wrong with the brass or bullet or the combination of the two. The crimp die is not there to swage an oversized bullet/brass combo.

+1,000,000

The word "crimp" is a misnomer; "flatten" is a better word. All you want to do with an autoloader cartridge is to remove the belling from the expander. You bring the case back to parallel.

 

[Bugs100]

Thanks I was trying to get a consistant crimp of .469 but evidently it isn't that important.

 

[Gammon]

I don't measure my crimp either. The crimp die leaves a mark on the case mouth. I set my die to leave a mark .035 to .040 wide, or about the width of a spark plug gap.

 

[adweisbe]

Well consistency with crimp will be a result of consistently sized bullets, consistent length brass (varies from brand to brand, lot to lot, generation to generation), and consistent brass thickness.

Brass in handgun cartridges supposedly doesn't change much in length over multiple reloads, but I have not checked this personally.

 

[TY43215]

Is there a difference in where you measure from Taper crimping for Semi's to roll crimping for revolvers?

I use the same crimp on all 45ACP rounds.

I don't measure crimp at all. I back out the die so that zero crimp is applied and then turn it in until the flare from the case mouth is removed. If further crimp is necessary to get the cartridge to feed/chamber then something is wrong with the brass or bullet or the combination of the two. The crimp die is not there to swage an oversized bullet/brass combo.

For those that do not think crimp makes a difference I suggest the following:

If you are getting unburned powder, try a tighter crimp for better burning.

If you are getting erratic Chrono results, try adjusting your crimp for more uniform loads. (If you are not chronographing your loads that is another problem waiting to happen)

If you are getting bullets that tumble, lighten your crimp a little.

To get the perfect load for my 38spl revolver, I needed to crimp until the bullets tumbled then back off just enough to solve the problem.

For my 357SIG loads, I use Frangible bullets. Too much crimp and you fracture the bullets. Too little, you have set back problems.

Crimp is part of the reloading process. Not measuring crimp can cause more problems than a novice reloader can ever imagine with ammunition that is used in a firearm used for more than casual plinking.

 

[RKG]

I'm not sure what value such measurements would have.

What you want to do is make up a dummy round: do everything except seating a primer and charging the case. Seat the bullet to spec OAL without a crimp. Now, with the seater plug backed out and the seated-but-not-crimped round in the shellholder and the ram run full up, screw in the seater die body until you just feel some contact with the case.

While this is going on, field strip the pistol for which you are loading and remove the barrel.

Now, and this takes some finesse (and a bunch of candidate dummies): slowly turn in the seater die body, about one-quarter of a turn at a time, until the round that comes out just drops easily in the chamber of your pistol. You have now made your dummy.

If this is the only pistol, lock the seater die body down, and make another dummy to confirm that it drops in but headspaces firmly. Now, with this round run up into the seater body, screw in the seater plug until it contacts the slug, and lock this down.

If you load for more than one pistol, mark your dummies and use them for adjusting the die when needed. With seater plug backed out, and die body backed out, run dummy up the ram. Screw seater body in until it contacts the case mouth and lock, then screw seater plug in until it contacts the slug and lock.

Don't loose your dummies.

 

[TY43215]

With seater plug backed out, and die body backed out, run dummy up the ram. Screw seater body in until it contacts the case mouth and lock, then screw seater plug in until it contacts the slug and lock.

Don't loose your dummies.

Many progressive presses in use like the Dillon 550 seat at their own station making this even easier.

 

[Mooney]

...man, after reading the process above, I'm glad I started with my Dillon.

Crimp has a lot to do with power factor, pressure, etc., not to mention unburnt powder, bullets pulling out of the case under recoil (will jam a revolver OR a semi-), or potential setback.

Gary's word is good on this one, echoes EVERYTHING I have heard regarding reloading from the writings of Mike Dillon and other well known names (and reloading manuals) to word on the street from other knowledgeable persons. To make a firearm function properly, one must have appropriate ammunition which does the same. It took me a while to find the right combo for my SW 625 and 745, it also makes USPSA major PF from my brother's SW 1911- never a problem feeding, with setback, or with "pulling".

 

[JimB]

factory

I agree with Eddie, a factory die returns the case to a industry standard
dimension. Period.

Nothing else and nothing fancy. For adjusing your die (?mfgr) call them
for insturctions or RTFM.. If you do not know what the acronym stands
for PM me.

 

[Gammon]

Things are getting awfully complcated here. All I do is adjust the crimp die to get the .035 to .040 mark on the case mouth and I'm done.

 

[adweisbe]

+1,000,000

The word "crimp" is a misnomer; "flatten" is a better word. All you want to do with an autoloader cartridge is to remove the belling from the expander. You bring the case back to parallel.

Here is a summation from Brain Enos on the issue.
http://www.brianenos.com/forums/index.php?showtopic=22178&view=findpost&p=262648

Back in the ol' days, when we didn't have the luxury of crimping as a separate operation, we'd adjust our combination seating/crimping die to remove the flare, hopefully without cramming the case mouth into the bullet too much. Then Mike Dillon came along and built machines that seated and crimped in separate stations! Wow - crazy stuff. And then he even started making dies that crimped auto-pistol cartridges correctly, that is to say didn't actually "crimp" at all, but simply removed the flare from the case, laying the (flared) case mouth perfectly flat against the bullet.

Unfortunately, somewhere during the taper crimp die's evolution (from the roll crimp die), no one bothered to rename it so as to not mislead folks, for generations.

Roll crimping should do just what the name implies - the case mouth is slightly (or sometimes drastically, in the case of a heavy recoiling revolver) rolled into the bullet's cannelure. Which helps prevent the bullet (in the unfired rounds) from moving forward in the case in a revolver. Since revolvers typically headspace on the rim, as long as the roll crimp doesn't deform the bullet's bearing surface, no harm is done with even a heavy roll crimp.

Since autoloaders headspace on the case mouth, however, the case mouth should never be crimped so that the case mouth penetrates into the bearing surface of the bullet. So in the case of an autoloading pistol, the "taper crimp die" should never actually crimp the case mouth into the bullet in any way whatsoever. The roll of the taper crimp die is to remove the flare previously applied to the case (in order to seat the bullet without shaving copper/lead) - returning the case mouth so that is snug down on the bullet, but not crimping the case mouth into the bullet at all.

After some experience one can learn to "see" (without tools) if this has been done correctly. (Either too much or too little.) But until then a good set of calipers will guide you as you adjust the "Flare Removing" die. Using the thin part of the calipers (near the tip), measure the loaded, flare-removed round's case mouth at the very end of the case. The result should be the sum of the bullet's diameter plus 2 times the case mouth's thickness. (Usually .010" for most cases. So in the 40 S&W, the Flare Removing measurement should be approx. .420". Or at the tightest, .419". And be sure to "roll the case mouth around," so you don't just measure it in one spot.

Actually (taper) crimping the case mouth into the bullet almost always results in a loss of accuracy. Not removing the flare enough results in malfunctions. Some gunsmith's will recommend "taper crimping" more than what was previously recommended, and that is easy to understand as to why.

If you remove the flare precisely as outlined as above and your pistol (still) has any sort of feeding malfunctions, I can say for sure that crimping the case mouth more is not the solution. Once I learned how to properly set this dimension, I never experienced any malfunctions due to not enough "taper crimp" in over 20+ years of shooting 20-40,000 rounds/year.
be

And here HSMITH explains why a taper crimp die cannot be used to increase case neck tension
The question was:

You just crimp the case mouth back to the bullet, that is IT. Any more than that is detrimental.

Would you care to share some data that shows the detremintal effects of crimping? What exactly is being degraded?

And HSMITH's answer:
http://www.thehighroad.org/showpost.php?p=2011976&postcount=16

Deavis, I apologize for skipping over your question, I didn't see it on the first pass.......

What will be degraded is case tension, bullet shape, gun reliability, accuracy and consistency. Well, not all of those things are going to jump out immediately with just a couple thou extra crimp, but they can all come and visit.

The primary problem, and one of the first to show up as you crimp tighter and tighter is loss of case tension. The bullet is made of lead and copper or straight lead, neither material has much memory meaning if you bend or shape them they don't spring back much if any. As you squeeze the case mouth down on the bullet the bullet is squeezed down too, the case mouth WILL spring back a couple thou while the bullet won't. Now the bullet isn't being gripped by the portion of the case that squeezed the bullet, less grip on the bullet and chances of setback get higher in a hurry. Setback scares me in 40, especially with a race rig costing several thousand dollars sporting a fully supported barrel. Set one back enough in your glock and odds are the case will fail, you lose a mag release and magazine, maybe some other fairly minor damage. Set one back enough in a fully supported gun and barrel bursting is a very real possibility, and it will probably damage the frame and slide beyond repair.

All of the case tension a 40 round will ever have is created in the sizing die, we take a little away when we bell the case already and darn sure don't want to take any more away than is absolutely necessary.

Reliability is another problem from overcrimping, the case needs to be able to headspace on the casemouth. If you have them crimped down hard and a round gets out ahead of the extractor it can jam the case itself in the leade of the chamber. Race guns are typically cut with long throats for long loaded ammo, and the problem is a little more likely with a long throat. This should not happen on a gun that is working properly, but if a gun is going to decide to mess up it will happen in a match on the clock. This happened to a guy recently, he zeroed the stage and it cost him dearly in the standings.

Hope this helps explain a couple reasons why crimping past just removing the bell is harmfull. If you have any questions let me know.

 

[TY43215]

Here is a summation from Brain Enos on the issue.
http://www.brianenos.com/forums/index.php?showtopic=22178&view=findpost&p=262648

And here HSMITH explains why a taper crimp die cannot be used to increase case neck tension
The question was:

And HSMITH's answer:
http://www.thehighroad.org/showpost.php?p=2011976&postcount=16

Very good information, Thanks. It also explains why, as primarily a revolver shooter, my ideas of crimp are different.

Regards,