357 Magnum Creep

I am sure its just an effect of the picture and angle but are you sure that they are all uniform in case length?

Yup, if the cases aren't same size, crimp will not be uniform.

Is that a taper crimp? Or maybe a modified? Im not familier with Dillon dies.

Neck tension is what primarily holds the bullet. I'd try reducing your flare. Crimp in pics does not appear to be heavy, but neither is your 13.8 powder charge. Most of the time with 158 jacketed, I can see the base of my bullet by the bulge in the case. I cannot see it in your pics. That is why I wonder about flare. Sizing die adjusted all the way down?

The first one doesn't look like it has any crimp at all. The third looks like a good crimp.

Just for grins and giggles, if you have a 38 Spl set, try the 38 for roll crimp.

The third cartridge looks good to me. The other two aren't seated deep enough for my liking. But if they're still creeping out, you might consider a Lee crimp die.

I honestly think it's the Dillon dies. It says they start as a taper crimp and if you keep increasing the crimp, it makes a roll crimp. Not sure about that.

So far I haven't been really impressed with my 44 magnum Dillon dies. I have got the crimp die cranked down pretty good to keep my 44 bullets from crimp jumping due to recoil. Using Lee dies in 357 magnum, I have no problem.

I've got lots of Dillon dies and for semi-auto rounds I think they are great. For sizing and seating, I think they are pretty good ( though I do like the fine adjustments of other seating dies better). As for their crimp dies, I have no problems with their taper crimp dies. For roll crimping my 44's, I'm going to switch to either a Lee Crimp die or a RCBS roll crimp die.

I'm glad someone else thinks it's a modified die also. That looked like a taper crimp to me. I have dedicated taper crimp die for .357mag and a dedicated roll crimp die for .357.
I don't like modified crimp dies.
Get a dedicated roll crimp die and see if you still have that problem.
And we just went through this with another member, but I will ask again, that brass looks like new, you did resize it, didn't you?

Keith Wygal said:

. . . the cases are not all the same sizes but I did sort the brass by head stamp and they are close. All seem to crimp nearly the same.

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Crimping (with a fixed die) is extremely sensitive to case length, moreso as the crimp gets heavier, so I would suggest trimming any brass you're going to crimp. Fortunately straightwall brass shrinks* very slowly, so you don't need to re-trim hardly ever.

*Yes, straightwall usually gets shorter over repeated firings.

If your cases aren't trimmed to the same length you are fighting a losing battle - regardless of die type. "Close" isn't good enough with revolver brass.

Lee FCD. 180grn XTP 1.589 OAL

first, get rid of the mag primers and use standard ones. second, those loaded rounds look like they have no neck tension. can you take your calipers and measure the case diameter @ where the bullet is seated and @ just below that. there should be a .004" difference in the two readings for good neck tension on the bullet. if you don't have this tension, crimp won't matter.

if you don't have the neck tension, we can help with that.

luck,

murf

Looks loke the taper crimp is at thebottom of the cannulre insted of in it.

I've never trimmed pistol brass. I use a Lee FCD for everything. No issues, and any load I work up with a decent bullet seems to be more accurate than I am.

I don't trim revolver brass either. And I've had good results from all the major brands of crimp die, including Dillon.

I personally have never experienced the OP's problem because I never go looking for it like he has! It is entirely possible that my loads normally exhibit .004 of "creep", but if it doesn't tie up the gun, doesn't affect accuracy, and is just generally completely unnoticeable without calipers, I just don't care.

I trim all revolver brass. I shoot exclusively cast bullets so I need the case mouth to roll into the crimp groove at the same spot for every round I load for bullet tension.

Keith Wygal said:

Thank you! I appreciate the tip! I figured this might be the case. I just ordered Lee Factory Crimp die and a case trimmer from Midway. So good thing I didn’t start reloading to save money...lol. I wanted to because I thought it would be fun... and I was right I really do enjoy it. And even with the set backs I think of it more as a challenge.

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The way magnum cartridges are priced around here, you can reload to save money, it just takes a while for that break even to occur...
I trim my magnum revolver cases because that roll crimp depends on a consistent case length. As others have asked, did you resize the cases and check them before and after resizing to see if the case diameter is decreased? For the magnum cartridges I don’t rely just on neck tension to prevent setback but there should be some. Good luck!