Importance of crimping 357 rounds?

[civilengr02]

I have recently purchased a Ruger GP 100 (6" stainless) in 357 magnum and would like to start reloading. Unfortunately, I don't have a good feel for the importance of crimping the bullets in place. I have read that a crimp is important for preventing bullets from withdrawing from cases when firing rounds. I have also read that a crimp is important because it allows slower burning powders to develop optimum pressure before the bullet leaves the case.

When I have experimented with dummy rounds, I find that an un-crimped bullet takes a significant amount of force, and many whacks with a RCBS bullet puller, to free from the case.

Is bullet withdrawal truly a concern with a tightly fit un-crimped bullet? If so, are there different degrees of acceptable crimping?

 

[joneb]

I trim my cases to 1.279" and crimp my .357 mag. reloads, never had a problem.

Hey, welcome aboard.

 

[Ol` Joe]

Trust me, a good crimp is valuble with stiff 357 loads. The 1st rd or two may not budge but, the last one in the cylinder is all you need to move to tie up the gun. Slower powders like H110 or possibly 2400 also benefit from a firm crimp to keep velocity varitions to a minimum. I put a firm crimp on all magnum revolver ammo, 357, 44, ect, no matter if mid-range plinkers or heavy hunting loads.

 

[Iron Sight]

Load all chambers in the cylinder. Fire all but the last round. Pull the last round and check if it has expanded in overall length.

Actually the Smith and Wesson Safety & Instruction Manual packed with new revolvers suggests this.

 

[JDGray]

Sorry, I thought you said trimming

Yes a good crimp is important.

 

[Sommerled]

Do crimp those magnum loads. If you have some commercial loads in .357 that are of good quality, like ones made for personal defense, examine the roll crimp on them and use that as a guide.

If you are a CE as you signature suggests, then you may want to treat yourself to a $120 chronograph and see for yourself what difference a proper and consistantly made crimp makes in the velocity and thus uniformity of your handloads.

 

[Walkalong]

Definitely crimp them well with the slower powders, but it also helps with the faster powders as well.

Welcome to THR

 

[DEDON45]

Crimp 'em... yeah, it's tough to pull the bullets, but I've only pulled them when making up dummy rounds to get the bullet seater and crimper set right.

 

[civilengr02]

Thanks for the info!

I just wanted to thank everyone for the shared info. I have been considering a choronograph, and now I think I have talked myself into buying one. I have reloaded cartridges for my 7x57 for years and never really thought too much about the affect different components may have on muzzle velocity. I have always had good luck just following bullet manufacturers reloading data. However, now that I am branching out into reloading for the revolver, I am interested in how each detail (different cases, bullets, primers, crimp strength, etc.) affects the muzzle velocity.

Thanks again.

 

[The Bushmaster]

As you have read and I can't add anymore to it...Yes. A firm crimp on .357 magnum and other magnum calibres is important...