Inconsistent crimp and COL for .357 Magnum

[klmshooterk]

I finally determined a proper load for my .357 Magnum with Sierra 125 gr bullet and AA#9 powder.

Now, I'm have trouble with getting a consistent crimp and COL.

I am using the Lee 3-die carbide .38 Special/.357 Magnum set in a single stage press. Per instructions, I set the COL first, back out the seater plug and screw in the die until it touches the brass shoulder, add 1/8 turn for the crimp, and reset the seater plug to get the previously determined COL. Everything looks good. I start to go through my prepared cases and I'm seeing very inconsistent results. Some bullets are seated too high and some too low. The variance is over +/-0.030" Most of the crimps are weak and I can push the bullet easily into the case. As I go through my prepared cases, I've tried screwing the die in to add more crimp, but the cases get deformed or the bullets get set too high. I've never experienced this before.

I'm thinking that maybe the wide, soft lead tip of the bullet is getting positioned differently in each case because the seater plug end is concave? Is there a flat end version of the seater plug?

Or, is the brass overworked and weak? Too many reloads?

Did I over-expand the case mouths? I took 5 cases and resize them, and did a minimal neck expansion, but it didn't seem to help.

I'm really at a loss as to the issue.

Thanks.

 

[Doug Beach]

You may be crimping too much, and buckling the case away from the bullet. I would recommend seating all your bullets with no crimp, and crimping as a separate step, preferably with a separate crimp die.
You also do need a seater plug that will consistently mate with the bullet.

 

[2506]

I have never had good results trying to seat and crimp pistol rounds at the same time and I have been loading 40+ years. Set the die up to not crimp by leaving the die above where the crimp starts. Then adjust the seating stem to seat the bullets where you want them. After all are seated screw the seating stem up out of the way and screw the die down to put the amount of crimp you want to use. If you go to load ammo for semi auto pistols get you a Lee Factory Crimp Die. This die is used to put a good taper crimp on the bullet but it also makes sure that the case is sized correctly and this has increased the function reliability greatly for me.

 

[Uncle Ed]

The vast majority of reloaders do not trim their pistol cases to the same length. So if you want the crimp to be equal on each case then trim them to the same length. I trim my revolver cases with heavy roll crimps for a uniform bullet grip. I do not trim my 9mm, 40S&W and 45 acp and only taper crimp enough to streamline the case mouth.

Always seat and crimp in separate operations this helps prevent bulged cases and OAL problems.

Lyman type "M" expanders work wonders and do not over expand the case mouth. The "M" type die also aids straight inline bullet seating.

The Lee factory crimp die with the carbide ring in the base is a "cheat" for people who do not trim their cases. The longer cases can bulge below the crimp and the carbide ring will size the bulge back down. The only problem with the Lee FCD is the larger cast bullets can be sized down in diameter. Meaning it works best with jacketed bullets of the proper diameter.

 

[Gun Smith]

Chances are your cases are different lengths, and that will cause variations in roll crimping. I used to trim all my handgun brass to the same length, but that is a pain. I went to a taper crimp die years ago for all my target handgun loads, as opposed to a roll crimp, all except heavy .41 and .44 Mag loads that is. Case length is less important with a taper crimp. The taper crimp die is much gentler on the brass, and in my experience using cast and swaged lead bullets, I got much less leading using a taper crimp, as a roll crimp seems to scrape the lead upon leaving the case.