45 Auto Crimping

[Horty]

I know that I have asked about 45 Auto crimping i the past but I have a new question. I have heard conflicting information about crimping 45 Auto. Some on this forum say to crimp it to .469 however I have heard (and read) elsewhere that you should not crimp a 45 Auto at all because it headspaces on the mouth of the case and therefore crimping can mess up the headspacing. What do you all think? Any comments?

 

[HiredHand]

Use a taper crimp die, adjusted to give enough tension to prevent bullet set back during feeding.

 

[1911user]

Don't think of it as crimping. Think of it as "unbelling" the case mouth. You bell (expand) the case mouth so a bullet can be seated. Undo that process (with a taper crimp die) and go no further. You'll be fine if the case mouth ends up at 0.469 inches.

If in doubt, measure the diameter of the bullet at the level of the case mouth when seated. Measure the thickness of the brass at the case mouth. "crimp" to the measured bullet diameter plus twice the case mouth thickness.

The final test is the ammo should drop freely into the firearm chamber. If it doesn't drop in freely, then slowly increase the crimp until it does.

 

[1911user]

Use a taper crimp die, adjusted to give enough tension to prevent bullet set back during feeding.

"Crimping" has nothing to do with bullet setback in semi-auto rounds. In fact, taper crimping even tighter will reduce the tension on the bullet; the brass springs back more than the bullet especially if it is soft lead or plated. Roll crimping revolver rounds is different and a tighter crimp will increase bullet pull.

Bullet tension is controlled when the case is resized then expanded (belled) for bullet seating. In the past, I found a combination of thin 9mm brass and jacketed bullets that required use of a special sizing die (sizes 0.001 inch smaller than normal). Otherwise I could push the bullets deeper into the case with only finger pressure. The problem was solved with the tighter sizing die.

 

[oneof79]

If you crimp to .469 at the mouth of the case, the round will still "headspace" on the case mouth. Try this, use your barrel as a case gage. Take it out of your gun and test seat some rounds in the barrel. The base of each round should be even with the hood of the barrel.

Then there is the camp that says the rounds headspaces off of the extractor.

 

[Blitzfike]

If you crimp to .469 at the mouth of the case, the round will still "headspace" on the case mouth. Try this, use your barrel as a case gage. Take it out of your gun and test seat some rounds in the barrel. The base of each round should be even with the hood of the barrel.

Then there is the camp that says the rounds headspaces off of the extractor.

This... and if you don't reduce the bell of the case mouth to around .469 you will have problems with feeding. Other than the .469 dimension, this applies to ALL the straight wall semi auto pistol rounds I load. Blitzfike