Can anybody help? 357 Magnum, Dillon dies...and roll crimp.

It may sound frightfully crude, but I would just look at a factory load and match the appearance.
You should have enough neck tension to prevent recoil from pulling bullets no matter the crimp.
Excessive roll crimp shows as a bulge at the crimp that can even prevent chambering.

Well the Dillon dies will do a roll crimp, but not like a traditional roll crimp. It starts out as a taper crimp and if you keep cranking it down it will roll crimp. I honestly don't like it as much as a Lee Factory crimp die. I use Dillon dies for my 38 specials and Lee dies for my 357's. I'll try to grab a close up pic of both crimps in a little bit.

Some great advice already given. Where I do not loade 357 mag, I do load 38 special and 44 special/mag. I have both Dillon, Lee dies, and a seating/crimp RCBS die.

I like the Dillon crimp for lighter loads, especially with 38 and 44 special. The Lee Factory Crimp die is better at getting a fairly aggressive crimp on those super hot loads.

To make things even more confusing, I use a Lee collet crimp die for 460 magnum as it takes a TON of crimp to hold those flaming hot loads in place.

My largest complaint with the Dillon dies? No fine adjustment. I often change my crimp on magnum loads based on the projectile and powder charge. Doing that on a Lee is easy money as you just turn a dial. On the Dillon? Yeah, not so easy, you have to adjust the entire die, which sucks.

So...a rock solid bit of advice is to look at factory magnum loads and see what they do. Ill be honest when I say that's what I first did. As time goes on, you'll figure out what works.

Jim said it all. I have loaded countless .357 rounds with Dillon dies in a Dillon progressive. Do what Jim says and you will be good.

If you're loading mild to mid .357 with a fast powder, crimp is less important, like 9mm

If you're loading loudenboomer .357 with H110 or so, you want to roll the mouth all the way into that cannelure and get starting pressure UP for consistent ignition

Typetwelve said:

My largest complaint with the Dillon dies? No fine adjustment. I often change my crimp on magnum loads based on the projectile and powder charge. Doing that on a Lee is easy money as you just turn a dial. On the Dillon? Yeah, not so easy, you have to adjust the entire die, which sucks.

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Oh, yeah. I have Hornady seating dies with Microjust stem... about half the price of Redding and adequate for my needs.
I used Lyman seating dies for a while, bought used die sets with obsolete steel sizers at gun shows to get them. Fine pitch threads on seating plug are a help but no graduations.

I wouldnt expext any projectiles to pull out from recoil on a 357 mag, unless they are hot loads, heavy bullets, and a very light revolver

VV says magnum primer.

@Walkalong provides the best advice on crimping. Here is a photo of his. Medium crimp on a Hornady bullet.

I agree with Jim again. Magnum primers are a great idea with that powder.

Crimped all to hell. What die?

Roll crimping is an art in itself and I'm still working on my technique.
The temptation to 'roll it like ya mean it!' is strong, but I'm finding one needs to keep it kind of subtle.
IMHO, it needs to look more like the brass was gently vacuumed down into the crimp groove vs. having tooling marks visible on the brass.

@Walkalong has some great pics, doesn’t he? One other thing I’ve found is consistency of roll crimps depends on having very similar case lengths. Either trim brass before roll crimps, or be very lucky with the cases being the same length. I use RCBS dies for my roll crimp, and they work pretty well. Good luck!

The picture of your round shows you screwed in the crimp die way too far, that is why it looks flat at the case mouth.

Dillon has two dies one for seating and one for crimping.

That is why they lack the fine seating stem, because the do not need it. First get the seating depth correct in the seating die. The depth should be so that the edge of the case mouth is on the crimp groove in your bullet.
Now follow directions for the crimp die. Raise the ram and screw the crimp die down until it touches the case and you feel resistance. Lower the ram and screw the die in 1/4 turn, raise the ram and check your round, it should have a nice roll crimp. If not adjust a little at a time until it does.

There is never a need for a lee factory crimp die unless you are doing something wrong. Fix what you are doing instead.

@Damon Larsen that looks just like mine when I use Dillon dies.

@Walkalong are your crimps done with a Dillon die? I only ask because neither my Dillon 357 dies or my Dillon 44 mag dies will produce a nice roll crimp like your pictures. They all have the same look as Damon's. If I use my dad's RCBS dies I get the nice roll crimp.

Damon Larsen said:

What is the method to know you’ve applied the right amount?

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Reloading is part art, part science.
Roll crimping is the art of reloading.

Do a search here & look & read.
IMHO this is too much.

I have some factory 357mag that have no crimp at all. In addition to the neck tension, they used some sort of glue to hold the bullet in place, though.

I am a firm believer in the Lee collet crimp die (not the normal FCD). It does not have the carbide resizing ring, so you don’t have to worry about swaging down slightly oversized cast bullets. And it also doesn’t depend as much on consistent trim lengths to get a good crimp. It is even possible to get a good crimp on plated bullets without a cannelure, without breaking the plating,