How much crimp is enough?

[jason867]

Here's two examples of some crimp that I applied to a 38sp and 357mag.

The silver 38sp has significantly more crimp than the brass 357mag.

So which is considered heavy or strong crimp? I've noticed buffalo bore 180gr cast 357mag cartridges that are crimped like the silver 38 in my picture below, and they're loaded HOT...

Just wanted to get some clarification...

http://img816.imageshack.us/img816/9008/1001669.jpg

[1bluehorse]

The nickel brass looks way to firm to me, (the flat area below the case mouth) the brass one appears as if it would be okay for a "heavy" load as well as I can tell from the photos, but almost appears to be bulging the brass.

[wallenba]

This question arises frequently. Unless you are trying to build more pressure, a crimp that keeps the boolit from pulling out under recoil is all you need. To achieve that, experimenting is the best way. Load a couple of rounds with varying crimp keeping track of what is what with magic marker color on the cases. Load with some factory rounds ahead of them. Shoot the factories one at a time checking the handloads successively for change in length. That will build your confidence in what is adequate or not.

[jason867]

Well I'm applying the crimp with a lee factory crimp die. As I assume you know, it also sizes the whole cartridge. As far as I can see there is no bulging going on...

Also, I don't size the bullets I cast, I just make sure they're fat enough.

I'm not worried about the bullet moving, because I haven't had problems with the bullets moving on me yet. What I'm concerned about is I've read that a strong crimp is necessary for slow powders to burn properly. I just don't know what constitutes a strong crimp. Most ammo I've seen has the lighter crimp in my picture. However, like I said, the buffalo bore cast 180gr mag ammo I tried had a strong crimp like the silver cartridge in my picture. It was very hot stuff.

[theperfessor]

Case neck tension is a much bigger factor in holding a bullet in place than the crimp. Too much crimp can either size down the bullet or bulge the case at the neck area and actually loosen the bullet/neck fit. I've seen roll crimped rounds that you could spin the bullet in the case. And taper crimps - too much and you size down the bullet and the case both, and then the brass springs back to a greater extent than the bullet and things loosen up again.

If you need to get more neck tension than you can achieve without sizing down the bullet then you need to get a harder bullet.

[btroj]

Bullet pull depends on way more than crimp. The size of your expander is what determines pull in most cases. The crimp can make a difference but do not get lulled to sleep by it. Bullet pull is a multi faceted things and all factors need to be addressed for a happy load.

[runfiverun]

the nickel case looks like it was squished in there with some side cutters or something.
the brass one looks like a good firm roll crimp.
i use a bit less than that for revolvers and leverguns.
for most of the target stuff i use no crimp at all.
it's amazing how hard it is to pull a swc from a case.

[Fixxah]

DukeInMaine has a slick way of finding the right amount of crimp that you will find useful. If this doesn't make sense send him a PM.

Set up a white paper target 8' away and fire a round at it. If you have enough crimp, there will be nothing but a hole in the paper. Not enough crimp and there will be powder residue along with the hole.

[44man]

Way too much crimp! You only ruin brass and the boolit.
Case tension is what is needed so don't ruin that. DO NOT SIZE WHEN CRIMPING.
All you need to do is to close the edge of the brass until it is in the groove, go no farther. A decent roll crimp is all you need.
Crimp does NOT aid powder burn, only case tension is needed.
If you still see some crimp left on fired brass, you are well over what you need and have ruined the boolit.
Case tension needs a harder boolit and you should see the boolit base and even the grease grooves through the brass, never look for smooth brass. All your loads need to do is chamber.
I use a gentle roll crimp on the .44, .45, .454, .475, .500 JRH, and .500 Linebaugh. The only gun we have trouble with is the .50 Alaskan with heavy boolits or factory .454 loads that are over crimped.

[jason867]

Your opinion contradicts the general consensus, from everywhere I've looked, not just here at cast boolits.

I've looked at several forums and have noted many people, including several who seem to be very credible, that believe that a heavy crimp, that looks similar to the 38 in my pic, is needed for slower powders, in both the 38 & 357.

Obviously less is needed for faster powders.

[stubert]

I second 44man, To much crimp. I load for 45-70 marlin and 44 mag. ( to name a few) The crimp on the brass case is excessive. I shoot 310 gr Lee's from the 44 mag. Redhawk and 405 gr. from the Marlin 1895, I've never had a boolit move under recoil. Also, I would lose the Lee full sizer die, if you can chamber your cases without using it, you don't need it. Give it a little bit of roll crimp, you'll be fine.

[Cherokee]

I've heard "heavy crimp for slow powers" all my 50 years of reloading. Never had a problem with bullet movement if there was sufficient neck tension with just enough crimp to roll the case mouth into the crimp groove.

[jason867]

I'm not concerned about bullet movement, I've never had a problem with it yet.

I'm concerned about the slow powders burning properly.

Regardless, I think I've got a good grasp of what a heavy crimp is supposed to be, so I'm gonna just test it out for myself.

[dla]

Start pressure and bullet jump. I have an S&W329pd that is a great kinetic bullet puller on ammo without a stout crimp. I'm not convinced that a simple roll crimp is adequate for that revolver and full-house ammo.

The cartridge on the left appears to be crimped with a Lee FCD. That bullet won't move due to recoil. And it helps with igniting H110/296 when it is -10*F.

I wished I knew enough to tell you whether or not the heavy FCD crimp negatively impacts accuracy.

[blackthorn]

Quote "Well I'm applying the crimp with a lee factory crimp die. As I assume you know, it also sizes the whole cartridge. As far as I can see there is no bulging going on...

Also, I don't size the bullets I cast, I just make sure they're fat enough"

If you are making sure your bullets are "fat enough" and then running the round through a Lee FCD, you just sized your "fat enough" bullet down! There are numerous posts around disscussing the use of Lee FCD for handgun ammunition and it's short-falls. Do a search on the FCD and one on crimping.

Oh yes---welcome to the forum.

[madsenshooter]

Good question, what size is the fat enough bullet now? Sounds like a job for the kinetic puller.

[44man]

Lee boolits have a scratch for a crimp groove, yet I shoot the .475 without any boolit pull even if I remove the last load and cycle it for another cylinder full.
Brass is really weak and to think a harder crimp makes it hold a boolit better then the tension on the length of the boolit is folly.
Yet brass is harder then lead so if you crimp too hard, the brass will not open fully and the lead will be sized going through the crimp.
I will never understand why anyone thinks crimp aids powder burn. I use nothing but 296 and would never think about crimp other then to hold a boolit in under recoil.

[jason867]

The bullets start out between .358" & .360" at the rear band, as cast. usually slightly oblong.

After seating, crimping, and pulling back out, they measure about .357" at the rear band.

But what does that matter? Upon firing, the base should obturate and engage the rifling, helping with accuracy and leading.

by the way madsenshooter, I formally invite you to the Indiana Gun Owners (INGO) forum:
http://ingunowners.com/forums/

You'll find me there under the same username.

[edit] nevermind, just found your username there...