44 Mag: what's a firm crimp?


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larryw
January 14, 2003, 08:57 PM
How do you measure a firm crimp in 44 Mag? My loaded cartridge measures .453 at the bullet bulge and .450 at the mouth. Crimp is right at the groove. .

Empty case measures .013 at the mouth, using Horandy 240gr XTP CL-SIL bullet.

These function great in my Redhawk, but I just got a 1894 in 44 Mag and want to make sure I don't get setback in the tube magazine.

Does this sound like enough crimp?

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Poodleshooter
January 14, 2003, 11:42 PM
I test my 30/30's (for tubular magazine) by measuring OAL, resting the bullet tip on a hard surface, and leaning weight onto it, then remeasuring OAL. I have never seen one of those setback from my test, or in my rifle. Perhaps that would work for you?

Mal H
January 15, 2003, 12:30 AM
larry, As you know, the rounds in a tubular magazine are held in place under spring tension, a fairly light spring at that. So as the rifle recoils, the inertia of the cartridges will make them push against the spring as a group. They won't move very far forward in the tube, so as they are pushed back by the spring after recoil there won't be much pressure on the bottom cartridge by the ones on top. There should actually be less tendency to setback in your '94 as in your Redhawk where they are held firmly in place. And, since you are crimping in a groove, there isn't much chance of setback in either gun.

larryw
January 15, 2003, 01:09 AM
Thanks guys, makes sense. The push test didn't budge the bullet, so my new shoulder thrashing 44 rifle probably won't cause any problems. :D

However, on further thought, the question remains, some powers (IIRC, ex. H110) require a firm crimp to burn properly. What's a firm crimp?

thanks,
LW

stans
January 15, 2003, 08:27 AM
For me, a firm or heavy crimp occurs when the case mouth is rolled tightly against the bullet crimping groove or cannelure. I take the average thickness of the case mouth, multiply by 2 then add the diameter of the crimping groove. This gives me the diameter of the crimped case mouth.

Odessa
January 15, 2003, 09:09 AM
Larry, get a factory round and look at it - the crimp will be visibly rolled into the bullet cannelure - my method is to crimp it tight enough so that I can see the crimp. That method has worked successfully for me for near max .357 Mags, .41 Mags, and .45 Colts for years. Odessa

tex_n_cal
January 15, 2003, 11:42 PM
A firm crimp?

You tighten it down until the case starts to collapse, then you back off 1/8 turn.

:D I'm sort of kidding.

You may want to consider the issue not just of crimping, but also die expander size. I like the expander plug to be at least .005 to .007" smaller than bullet diameter. A tight crimp cannot replace a tight bullet fit.

larryw
January 16, 2003, 01:50 AM
Measurements and math: good stuff, thanks!

tex_n_cal your sig line has always been one of my favorites (and describes my favorite heavy Cab to a T). :D

WESHOOT2
January 16, 2003, 07:33 PM
When firing revolver ammo bullets 'pull' forward.

Highly recommend measuring and marking one round per cylinder and re-measuring after firing the rest of the cylinder.

I like the 'crush and back off' method; Redding Profile Crimp die.

Mal H
January 16, 2003, 08:04 PM
Right you are, Tim. I was thinking about that a short while after I posted a few days ago. But, I left the word 'setback' in the post to indicate a the-bullet-is-moving-in-the-case problem. :)

(Actually, laziness and the posting time outs also had a lot to do with leaving it as is. ;) )

mete
January 17, 2003, 11:48 AM
Properly loaded the case should grip the bullet tightly and there should be satisfactory crimp. Without a proper grip on the case you may not get proper combustion of the powder and the bullet may move in the magazine/cylinder. Excessive crimp especially with lead bullets may distort the bullet and affect accuracy.

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