CRIMP - if some is good, more is better, too much...just right!

[subsonic]

A very good friend sold his Delta Elite and gave me the loaded 10mm ammo he had left. He and I have been friends forever and often spend hours discussing reloading, guns, beer, etc, so I had a pretty good idea what was in the loads, but still felt it prudent to pull a bullet since the boxes were not marked.

Since my inertial hammer type bullet puller will toss powder all over, I prefer to use my press and a pair of vice grips to pull bullets and boolits when possible if I'm trying to recover or measure the powder.

I was surprised what I found when I pulled these. Take a look. You can see where the mouth of the case cut into the jackets and on a couple, you can see where the case mouth scraped the plating off of the bullet core during seating (probably from lack of expanding/belling).

http://i1179.photobucket.com/albums/x386/Dennis_Doza/crimp.jpg

Most of these are "plated" but the XTPs were squeezed down and mangled as well. Imagine what happens to a cast boolit when you turn the taper crimp die in a bit far....

You get two guesses as to how well the rest of these shot, but I think you'll only need one of them.

[44man]

Very good pictures.
Just yesterday a friend came to shoot and I was shooting his gun. SRH, I had a lot of fliers so I checked his loads. Some were crimped too much and some even were crimped in different places on the boolit, brass buckled.
I picked out the best and they shot OK and I showed how bad the others shot.
I sat him down and showed how to load. Now this will tickle you! I seated a boolit and unscrewed the seating plug to set crimp. I FORGOT TO RESET THE PLUG! :holysheep I proceeded to seat and crimp a few more and by 100% luck, they were the perfect depth. I even had to look at them again this morning, that just can't happen!

[725]

Seems too much crimp swages the boolit down and adversely affects performance. Just like the three little bears, you have to find the one that's "juuuuuuuuuuuuust right".

[Lefty SRH]

How do you know when you have it "just right"?

[subsonic]

How do you know when you have it "just right"?

You have to experiment. Crimp and then pull one. See if it has mangled your boolit or bullet.

For a taper crimp, you can also measure the OD of the crimped round at the case mouth with calipers or a micrometer. You don't want it much smaller, like .0005" (yes, 3 zeros, half a thou) than the case diameter over the boolit shank when seated - for cast. The case neck tension should really do the work, not the crimp. The crimp should simply turn the belled portion back in.

Roll crimp should fold into the crimp groove without buckling the case. Slide your caliper jaws over the case toward the crimp. You will probably see little swings on the caliper where the grease grooves and driving bands are. You should NOT see a little swing upward at the very bottom of the crimp. If the case is larger here, it has buckled, and you have lost case neck tension. Don't beleive me? Over-crimp one and pull it. The boolit will come right out with little force.

And one other thing I'm noticing since I started paying attention, starting the boolit straight in the case has a MAJOR effect on seating force and resulting case neck tension. Seating even slightly crooked and allowing things to "self center" "wallows out" the case neck. Since I have switched to Hornady seating dies with the floating sleeve, case neck tension has become much more consistent and seated boolit runout has improved - as has accuracy.

[44man]

You have to experiment. Crimp and then pull one. See if it has mangled your boolit or bullet.

You can also measure the OD of the crimped round at the case mouth with calipers or a micrometer. You don't want it much smaller, like .0005" (yes, 3 zeros, half a thou) than the case diameter over the boolit shank when seated - for cast. The case neck tension should really do the work, not the crimp. The crimp should simply turn the belled portion back in.

Roll crimp should fold into the crimp groove without buckling the case. Slide your caliper jaws over the case toward the crimp. You will probably see little swings on the caliper where the crimp groove and driving bands are. You should NOT see a little swing upward at the very bottom of the crimp. If the case is larger here, it has buckled, and you have lost case neck tension. Don't beleive me? Over-crimp one and pull it. The boolit will come right out with little force.

And one other thing I'm noticing since I started paying attention, starting the boolit straight in the case has a MAJOR effect on seating force and resulting case neck tension. Seating even slightly crooked and allowing things to "self center" "wallows out" the case neck. Since I have switched to Hornady seating dies with the floating sleeve, case neck tension has become much more consistent and seated boolit runout has improved - as has accuracy.
Best thing ever said! This should be a sticky.
Here is a perfect crimp---can you see it? Not much to show is there, Some will ask "what crimp" yet case tension is there. This 330 gr, .44 boolit will not pull from recoil.
A hated saying is "you need a hard crimp." Maybe it should be called "CRUMP."
Crimp has one function, to aid case tension to hold a boolit.

[subsonic]

Jim, I have to say that you were the one that sent me down this road to discover these things, and also you gave me some strong hints that these things are what I would find.

Thank you!

[Chicken Thief]

In the big thumpers ye need a wee bit of firm crimp ;-)

[subsonic]

In the big thumpers ye need a wee bit of firm crimp ;-)

Not really.

[sqlbullet]

I pulled a few Double Tap 135 grain 10mm's a few days ago and found similar results. Right below the shoulder they measured .394"

http://fellingfamily.net/images/DT_nosler135_pull-2.jpg

The base was still .400"+.

This box was old stock I found in my closet. At least 3-4 years old. Maybe they are different today.

FYI, the rounds were 1.245" long COAL, and the charge was 11.4 grains of what looked very, very, very much like Longshot. Brass was starline.

[44man]

In the big thumpers ye need a wee bit of firm crimp ;-)
How about a .500 JRH? Notice the case tension.
The worst I ever shot were factory .454 loads that had hard full profile crimps that went 2 to 3 shots before locking the gun. Sold for large game where you can get ATE fast. Not to be trusted at all. My .454 loads never pulled a single boolit.

[subsonic]

Taking this a different direction, how do you think the second bullet from the top in my first post would perform on game?

[44man]

I don't know. If it expands just right without losing penetration it will be good. I consider the .40 a brother to the .41 mag. It is bullet selection because so many are made for people.
I have a big problem unless I actually shoot a bunch of deer with any bullet/boolit.
The .40 is indeed a good gun but I don't know enough.

[subsonic]

I am refering to how the jacket has been completely cut in-two at the place the case mouth "bit" it.... I bet that whole front part comes off on impact!

[tek4260]

http://i292.photobucket.com/albums/mm35/tk3945/DSCN1122.jpg

All of my expander dies have been turned down a few thousandths.

[tek4260]

Actually, now I just size and deprime, the use a Lee universal expander to gently flare the case mouth just enough to accept the boolit. That way you don't get into the dies expanding the case mouth before they get to the point of flaring.

https://www.riflemagazine.com/magazine/article.cfm?tocid=1406&magid=96

[subsonic]

http://i292.photobucket.com/albums/mm35/tk3945/DSCN1122.jpg

All of my expander dies have been turned down a few thousandths.

That definitely can help! Some need it, some don't. It depends on your loading components as much as the brass. Oversize boolits are already a "tight fit". Maybe that's why they shoot better for some folks?

[subsonic]

Actually, now I just size and deprime, the use a Lee universal expander to gently flare the case mouth just enough to accept the boolit. That way you don't get into the dies expanding the case mouth before they get to the point of flaring.

https://www.riflemagazine.com/magazine/article.cfm?tocid=1406&magid=96

I have played with one of those, but I think they flare off-center sometimes, as there is nothing to line them up with the case. I prefer a proper expander that will also "round out" and "iron out" the case walls that centers-up off of the case ID.

My reloading die boxes are slowly changing from green to red....

[tek4260]

My cases don't have dents! :)

Like I said, just enough to keep from shaving so the centering isn't much of an issue, or at least hasn't shown up as one.

[subsonic]

I really need to set up my press to measure the force it takes to pull boolits....

[44man]

I am refering to how the jacket has been completely cut in-two at the place the case mouth "bit" it.... I bet that whole front part comes off on impact!
I didn't think of that and it would be a problem. Even if loaded without damage, the soft core and thin jacket might open too fast for hunting.

[35remington]

Since this was for an autoloading pistol cartridge, all we ask a taper crimp to do with the jacketed bullet is turn in the bell in the case mouth from the flaring step. It appears the seating die is a taper crimp seating die, and he was applying the taper crimp well before the bullet was seated in the case fully. Advice is to seat the bullet and taper crimp in separate steps to avoid problems. That way you are not trying to seat a bullet in a case that is becoming smaller than the bullet the further in the die it goes. This will scrape the sides of the bullet as seen in the picture.

Not good.

Try this test with a jacketed bullet:

Don't size the case. Use a bit of dacron to hold the bullet at the right level in the unsized case and crimp it with a "death crimp" in the taper crimp die.

Now tap the assembled cartridge, nose first, against your loading bench. The bullet will slide in the case easily. Since many mistakenly crimp jacketed bullets with taper crimps with the idea of resisting bullet setback in the case on feeding, this conclusively proves that the taper crimp does nothing to hold the bullet in place, most particularly when the bullet is jacketed. The jacketed bullet, even when excessively crimped, does not form a sharp shoulder to abut the case mouth. This rounded surface does not prevent setback.

Try it.

Cast bullets can be taper crimped so ferociously that a shoulder is formed in the bullet by the case mouth, and this shoulder does resist bullet setback even in an unsized case, but one might fairly ask what this does to the accuracy potential of a cast bullet. This excessive taper crimping is bad for revolver rounds as it reduces the amount of bullet engagement with the rifling as the bullet strikes the forcing cone, making the bullet more likely to skid excessively.

[subsonic]

Exactly.

[canyon-ghost]

To get the 41 magnum Blackhawk just right, I managed to create a hair-raising scenario. I crimped them lightly enough that the bullets began to move out of the case under recoil. When they did, the cylinder stopped. The solution there was to push the bullets back into the case, with my thumb, far enough for the cylinder to rotate.

Seriously, I was a bit taken aback. Here I was, pushing a lead bullet back into a case that I knew had a live primer and magnum powder charge! Nothing happened, thank you New Model Blackhawk. I finished shooting the cylinderful of offenders and left the range to go reset the die. * "Just a bit more, ya reckon?" * omg.

If it was safe, I probably wouldn't like it. But, that's "duck, incoming!".

Good Luck,
Ron

[km101]

I would pull ALL those bullets! With that much deformity they wont shoot worth a darn. And since the 10mm/ .40 headspaces on the case mouth, they could build up extreme pressure if the crimp is tight enough to let the case mouth enter the chamber. And it sure looks like it has been squeezed down enough that may be a possibility.

[44man]

To get the 41 magnum Blackhawk just right, I managed to create a hair-raising scenario. I crimped them lightly enough that the bullets began to move out of the case under recoil. When they did, the cylinder stopped. The solution there was to push the bullets back into the case, with my thumb, far enough for the cylinder to rotate.

Seriously, I was a bit taken aback. Here I was, pushing a lead bullet back into a case that I knew had a live primer and magnum powder charge! Nothing happened, thank you New Model Blackhawk. I finished shooting the cylinderful of offenders and left the range to go reset the die. * "Just a bit more, ya reckon?" * omg.

If it was safe, I probably wouldn't like it. But, that's "duck, incoming!".

Good Luck,
Ron
Total lack of case tension if you can push boolits back in with your thumb or just a stick. I bet you use RCBS dies! Other dies have expanders too large, made for soft lead. Jack up recoil and you are better off loading one shot at a time.
If any boolit moves a little even if it does not lock the gun, you change case capacity shot to shot.
More crimp will not help you at all.

[subsonic]

More crimp will not help you at all.

Yes, people misunderstand the ability of crimp. If you have a boolit with a long, deep crimp groove, say a keith type SWC, and give the maximum crimp without crupling the case, you are still only adding about 10% to the total force required to pull the boolit.

Yes, the shape and size of the crimp groove matters too.

[44man]

Yes, people misunderstand the ability of crimp. If you have a boolit with a long, deep crimp groove, say a keith type SWC, and give the maximum crimp without crupling the case, you are still only adding about 10% to the total force required to pull the boolit.

Yes, the shape and size of the crimp groove matters too.
Right on!
I shoot a lot of Lee boolits with chicken scratch crimp grooves with heavy recoil and boolits do not move. I have to adjust the crimp for them---LESS then other boolits.

[tek4260]

I wonder how much of the sized case below the base of the boolit helps with tension? I have considered decapping 44's in my 45 die then only sizing in the 44 die enough to go slightly below the boolit. That way, the case will better fit the chamber and help with alignment on a New Model without recessed case heads. I think it is kind of pointless on an OM since the recessed case heads will hold the rear of the case in alignment with the chamber, while the properly sized boolit holds the front in alignment with the throat.

[44man]

I wonder how much of the sized case below the base of the boolit helps with tension? I have considered decapping 44's in my 45 die then only sizing in the 44 die enough to go slightly below the boolit. That way, the case will better fit the chamber and help with alignment on a New Model without recessed case heads. I think it is kind of pointless on an OM since the recessed case heads will hold the rear of the case in alignment with the chamber, while the properly sized boolit holds the front in alignment with the throat.
I do a lot of neck sizing but have found no real advantage over FL. After neck sizing so long, cases get hard to chamber so I have to FL now and then. I just go ahead and FL for most of my guns.
My 45-70 brass is always FL sized because of case taper. I need the boolit portion reduced enough. I bought a Lyman neck die and it does not size enough, boolits are loose.

[Hammerhead]

To maximize bullet tension I use the Lee universal expander die (http://www.midwayusa.com/product/140461/lee-universal-neck-expanding-die) with jacketed revolver and auto ammo. It's just a cone shape tool that flares the case mouths without expanding the necks to give the bullets a start. The bullets do the expanding so bullet tension is maximized. Auto rounds made this way need no crimp and will pass any set back or recoil test. I still crimp revolver rounds with a light profile crimp.

[44man]

To maximize bullet tension I use the Lee universal expander die (http://www.midwayusa.com/product/140461/lee-universal-neck-expanding-die) with jacketed revolver and auto ammo. It's just a cone shape tool that flares the case mouths without expanding the necks to give the bullets a start. The bullets do the expanding so bullet tension is maximized. Auto rounds made this way need no crimp and will pass any set back or recoil test. I still crimp revolver rounds with a light profile crimp.
Doing good.