Trimming Handgun Case Tolerance

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islander

Bearcat
Joined
Feb 5, 2009
Messages
25
Location
Coral Gables Florida
Getting ready to load a batch of 38 special. Trimmed to good consistency but being new at trimming I do have some shorter cases within 0.005" of the trim length of 1.147", and some trial misfits off by 0.010". All cases are within the SAAMI length which is 1.155" - 1.135". The cases will be crimped with the Redding profile crimp die and used in a 357 mag. revolver.

Specific question I have is what should the case length tolerance be for good uniform crimps - 0.005" variation, or less?. Anything outside the tolerance range will be discarded but I need opinions from experienced reloaders about what to throw away, thanks.
 

Rifleman

Bearcat
Joined
May 13, 2004
Messages
23
Location
TN
I'd recommend loading up all your trimmed cases. The .010 variance from low to high likely won't cause any accuracy issues. Many guys NEVER check or trim handgun cases at all. I do, and trim them on occasion.
 

islander

Bearcat
Joined
Feb 5, 2009
Messages
25
Location
Coral Gables Florida
Thank you for that, accuracy of course is important. However, what I'm trying to learn about is uniform roll crimps. Case length variation as it relates to effective crimps.
 

flatgate

Hawkeye
Joined
Jun 18, 2001
Messages
6,784
Location
Star Valley, WY
IMHO,

You aren't loading ammo that's in need of much of a roll crimp. The fire belching loads in .41, .44 and bigger need very firm and consistent crimps to insure no "bullet pulling" due to the robust recoil.

Yes, of course, varying case lengths effect the crimp, as you suspected.

I don't look at trimming my brass until I start seeing a variance in my crimps or, usually, by the fact that one feels the difference in the press during the crimp application.

And, a good crimp die is paramount, i.e. Lee or Redding "4th die" style.

Again, JMHO,

flatgate
 

Rifleman

Bearcat
Joined
May 13, 2004
Messages
23
Location
TN
Flatgate is correct, using a good crimp die is very important. You might also consider setting your crimp to the mid-point case length for the cases you have ready. That way, the variation in crimp would be minimized.
 

Driftwood Johnson

Blackhawk
Joined
Sep 25, 2007
Messages
699
Location
Land of the Pilgrims
Howdy

I'm one of those guys who never trims cases. At 38 Special pressures, they just don't grow at all. I bought a case trimmer when I first started loading ammo about 10 years ago, but after measuring cases that had been fired a bunch of times I just didn't see any growth. So I never trim revolver cases.

Rifle ammo is a different story.

If you have a little bit of variation in case length, the idea of setting your dies with the median length is a good one.

And just so you know, I also don't use a separate crimp die. It is simple to get good crimps using a conventional seating/crimp die. You just have to follow the instructions that came with the die. To figure out how much crimp you need, compare your crimps with factory crimps. Make them look the same. Don't over crimp, overcrimping can result in crimps that bulge a bit making ammo difficult to chamber. When you are setting your dies, make some dummy rounds to get your settings correct. Sacrifice a few bullets and cases without powder or primers to get your settings correct. Then put the dummy rounds away as references if you have to change the settings for a different style of bullet.
 
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