Roll Crimping

[buyobuyo]

I'm setting up my dies to start loading .38, and I'm not sure if I'm setting up the roll crimp properly.

What I'm doing is seating the boolit until the case mouth is just past the crimp groove, like so:



Which gives me a COAL of 1.520. Then I take out the seater plug and start turning in the die body an 1/8 turn at a time until I get what I think looks like a good crimp.



However, the problem I'm having is that the boolit is being set back 0.018" and there is a 0.003" bulge where the crimp rolls over compared to where the rest of the boolit is in the case. Backing the die out 1/8 turn still has the 0.003" bulge, and the crimp doesn't look adequate. Either way, the rounds chamber fine in my revolver.

Edit: Last night when I first tried setting up the dies, I was setting the initial seating depth at 1.500 and got the same 0.018" setup and bulge. The boolits are sized at 0.3578".

[MikeS]

You have to seat the boolit deeper so it's almost to the top of the crimp groove. Try that, and it should solve your problem. Also, what kind of handgun are you loading for? I could be wrong, but I believe that boolits with 2 crimp grooves such as yours are designed so that you should use the upper crimp groove unless you're loading 38 Special brass to be shot in a 357 Magnum gun. In either case, when seating the boolit your case edge should be further into the crimp groove than you're setting it.

[white eagle]

from the first photo looks as though you are rite on top of the
crimp groove
try to get in the center or just below the top of the next groove

[buyobuyo]

That's what I was doing yesterday evening when I was seating to boolits to 1.500". I'll give it another try and see what happens.

[Charlie Two Tracks]

Your OAL will be determined by your crimp groove. Those look like Mihec boolits. Is that a 158 grain?

[buyobuyo]

Boolit seated at 1.499"


Enough flare removed that the round will chamber


Roll just starting to form. No bulge. COAL same.


Bulge 0.001". Same COAL.


Bulge 0.001". Boolit setback 0.002".


Bulge 0.002". Boolit setback 0.007".


In the final picture the die is 1 full turn in from touching the case mouth.

[buyobuyo]

Your OAL will be determined by your crimp groove. Those look like Mihec boolits. Is that a 158 grain?

You are correct; it is a Mihec mould. It is the 359640-HP mould. Spec weight is 160gr. They drop from the mold at 163gr with my alloy. The boolit features two crimp grooves, and I am trying to use the lower groove for some long .38 rounds since they will be fired out of a .357 revolver.

[462]

Are you seating and crimping in the same operation? If so, do them in two seperate operations, instead.

[buyobuyo]

Right now I'm just trying to setup the die, but I am trying to set it up to seat and crimp in the same step.

I've been seating the boolit then taking out the seater plug and adjusting the die body down to set the crimp.

[white eagle]

if you are getting the bullet pushed back you are hitting something while seating
the boolit
may have to shorten it up even more
try seating at the last crimp groove one time

[turbo1889]

The back bulge directly behind the crimp is unavoidable unless you have a very tight tolerance die set. For every action there is an equal and opposite reaction. Pinch and roll down the mouth of the brass and the tension leverage in the metal is going to create that slight bulge below the crimp unless the die wall is squeaky tight up against it to prevent it. The deeper and more rolled the crimp is the more leverage stress in the metal of the case. The only crimp dies I know of that are set up tight enough around the top of the case neck to prevent that slight bulge below a deep crimp is some of the collet crimp dies where the collet tightens down around the top of the case while it crimps and if you adjust them just right to just kiss the outside of the case at top dead center on your press they will crimp without giving you a slight bulge below the crimp on a deep hard crimp.

Long story short, don’t worry about that part of the situation unless you are totally anal and are willing to special order a collet crimp die for 38-spl. Now I do think your bullet needs to be seated just a little deeper before you turn down the whole die to set the crimp since upon completion of the crimp the mouth of the case isn’t in the bottom of the crimp groove. I personally don’t like deep crimp grooves like that boolit of yours has but regardless you do want the mouth of the case to butt up against the top of the crimp groove so the crimp prevents the boolit from moving in either direction either out of the case or deeper down inside. From your picture it looks to be that the way your crimps are turning out the boolit could be pushed back a little in the case and the crimp won’t prevent this.

As to which crimp grove to use on a boolit with multiple crimp grooves. I personally prefer to use the crimp groove that gives me the longest cartridge over all length I can get away with in the particular gun in question. Deeper seating to use the crimp groove(s) further up the nose only serves to reduce powder space and potentially increase pressure and puts the boolit further away from the rifling. All things to be avoided if possible in my book. In fact my most recent custom boolit mold has four small short shallow crimp grooves allowing me a greater number of options for crimp location to get the boolit as close to the rifling as possible for each firearm depending on what the throat allows on each of them and allows me to use a nice gentle crimp and not crimp to the depths of hell itself and work the living daylights out of my brass. Granted some powerful heavy recoil cartridges do need a heavy crimp but done properly it is amazing how little crimp is needed in most cases.

[turbo1889]

Okay, need to hit the refresh button next time before I post on a thread I have had sitting in its own tab for well over an hour. Your second set of photos look much better for the end of the case mouth being tight up against the top of the crimp groove you are crimping in so the boolit can’t be pushed deeper into the case as well as can’t creep forward under recoil.

[turbo1889]

if you are getting the bullet pushed back you are hitting something while seating
the boolit
may have to shorten it up even more
try seating at the last crimp groove one time

He is seating and crimping in one step instead of two so by definition the boolit will be being set-back further while the case is being crimped. The important thing when setting up to seat and crimp in the same step is to set up the die so that the COAL is where you want it to be at the completion of the crimp rather then before the crimp since the crimp is made in the last little bit of upward movement of the press ram which means the boolit is seated just a little bit deeper while it is being crimped.

[buyobuyo]

if you are getting the bullet pushed back you are hitting something while seating
the boolit
may have to shorten it up even more
try seating at the last crimp groove one time

I'll give it a try and see if the bullet setback issue goes away

The back bulge directly behind the crimp is unavoidable unless you have a very tight tolerance die set. For every action there is an equal and opposite reaction. Pinch and roll down the mouth of the brass and the tension leverage in the metal is going to create that slight bulge below the crimp unless the die wall is squeaky tight up against it to prevent it. The deeper and more rolled the crimp is the more leverage stress in the metal of the case. The only crimp dies I know of that are set up tight enough around the top of the case neck to prevent that slight bulge below a deep crimp is some of the collet crimp dies where the collet tightens down around the top of the case while it crimps and if you adjust them just right to just kiss the outside of the case at top dead center on your press they will crimp without giving you a slight bulge below the crimp on a deep hard crimp.

Long story short, don’t worry about that part of the situation unless you are totally anal and are willing to special order a collet crimp die for 38-spl. Now I do think your bullet needs to be seated just a little deeper before you turn down the whole die to set the crimp since upon completion of the crimp the mouth of the case isn’t in the bottom of the crimp groove. I personally don’t like deep crimp grooves like that boolit of yours has but regardless you do want the mouth of the case to butt up against the top of the crimp groove so the crimp prevents the boolit from moving in either direction either out of the case or deeper down inside. From your picture it looks to be that the way your crimps are turning out the boolit could be pushed back a little in the case and the crimp won’t prevent this.

As to which crimp grove to use on a boolit with multiple crimp grooves. I personally prefer to use the crimp groove that gives me the longest cartridge over all length I can get away with in the particular gun in question. Deeper seating to use the crimp groove(s) further up the nose only serves to reduce powder space and potentially increase pressure and puts the boolit further away from the rifling. All things to be avoided if possible in my book. In fact my most recent custom boolit mold has four small short shallow crimp grooves allowing me a greater number of options for crimp location to get the boolit as close to the rifling as possible for each firearm depending on what the throat allows on each of them and allows me to use a nice gentle crimp and not crimp to the depths of hell itself and work the living daylights out of my brass. Granted some powerful heavy recoil cartridges do need a heavy crimp but done properly it is amazing how little crimp is needed in most cases.

Thanks for the info. I was thinking the bulge might be unavoidable. Everything I've loaded until now has been either lightly taper crimped or no crimp, so I wasn't 100% sure. I also read posts on here stating there shouldn't be a bulge. If I hadn't seen those posts, I probably wouldn't have worried about it or even measured to see if there was a bulge as long as the rounds chambered.

I too am a fan of loading long if I can, hence why I'm trying to use to lower crimp groove.

[buyobuyo]

He is seating and crimping in one step instead of two so by definition the boolit will be being set-back further while the case is being crimped. The important thing when setting up to seat and crimp in the same step is to set up the die so that the COAL is where you want it to be at the completion of the crimp rather then before the crimp since the crimp is made in the last little bit of upward movement of the press ram which means the boolit is seated just a little bit deeper while it is being crimped.

Actually...

Right now I'm just trying to setup the die, but I am trying to set it up to seat and crimp in the same step.

I've been seating the boolit then taking out the seater plug and adjusting the die body down to set the crimp.

However, I don't see any marks on the boolit to suggest that it is rubbing or hitting the die anywhere. Could it be just a function of the case mouth folding in and the crimp itself seating the boolit a little deeper?

[MikeS]

Looks to me like you went a bit too far in seating depth in the second set of pictures. Try seating the boolit half way between the 2 sets of pictures you've posted. You want the edge of the cartridge case to roll into the crimp groove, so there has to be room for it to do so. In your first set the cartridge edge was too low, in the second set it was too high. If you get it in the middle, you should be able to crimp without too much of a bulge. Even with the bulge, if you can chamber the round, than I wouldn't worry about the bulge, the only time it becomes a problem is if it keeps you from chambering a round.

[turbo1889]

. . . I don't see any marks on the boolit to suggest that it is rubbing or hitting the die anywhere. Could it be just a function of the case mouth folding in and the crimp itself seating the boolit a little deeper?

Didn't catch the part about you pulling the seater plug from the die, sorry about that what white eagle said makes a whole lot more sense now.

It could possibly be the roll crimp itself but you should also check the inside diameter of the crimp ring lip in your die set. Take one of your boolits and try to drop it through the top of the die (you have the top opened up right since you pulled the seating plug) and see if it drops right through or if the inside diameter of the ring lip that forms the crimp is smaller then the diameter of your boolits. If it is it could be catching on the boolit and pushing it deeper. I have had that happen to me on several die sets. The cure is quick and simple. Just take a strip of sandpaper and roll it up with the rough part on the outside and slip it inside that crimp lip ring and give it a couple twists and check to see if you have enough clearance for your boolit diameter. Couple twists, check with boolit, couple twists, check with boolit, etc. Should only take a couple thousandths of an inch or less to get the clearance you need if this is the problem so the inside diameter of the crimp lip ring inside the die isn't smaller then your boolit diameter. Had that happen plenty of times when I was using 0.359” diameter boolits and the inside diameter of the crimp ring lip was like 0.358” on a 357-mag die set or 0.455” diameter boolits with a 45-Colt die set that only had clearance for 0.454” diameter boolits, etc . . .

[MikeS]

Turbo: When crimping in a deep crimp groove like this boolit has, if the case mouth is in the proper position there shouldn't be any bulge. I've loaded several 45LC using a 452423 mould that also has a very large crimp groove, and I have no bulge by the case mouth. The only time I get a bulge is if I'm putting a heavy crimp on a boolit with a small crimp groove.

[buyobuyo]

Turbo, I just tried dropping a few unsized/unlubed boolits (~0.360") through the die. Most fall freely though, and the ones that don't get most of the way though. They hang up with the lower driving band at or just past the crimp ring lip and push through easily with light pressure, so the crimp ring lip should be large enough. I'll talk to a few machinists I know to see if they have a set of pin gauges that I could use to check it to know for sure. Additionally, I measured a few boolits at the crimp grooves, and they measure ~0.355".

Mike, I'll try a starting seating depth more in the middle of the crimp grooves when I put the die back together.

[williamwaco]

Long story short.
Seating and crimping in separate operations is a good thing if you have the patience.


One question.

After you seat to the correct ( desired ) depth.

Before re adjusting the die body to crimp, you MUST back the seating stem out three or four turns.

Are you doing that?