Crimp Test: Plated Pistol Bullets

[Steve Koski]

I did a home test to test the theory that over crimping actually decreases the case-bullet connection. I made two groups of cartridges, normal and super hard crimp, then I chambered them multiple times in a pistol and measured the change in COL.

A
I made 3 rounds with my normal 9mm crimp, once fired Speer brass, 124 grain Xtreme plated bullets, all 1.153" COLs. This is group A. Case mouths all measured .377"

D
I turned the crimp die down a FULL turn. Made 3 more rounds. This is group D. D's COLs were less consistent, at 1.155, 1.156, and 1.154. Case mouths measured .366, .366, and .365".

I then chambered all of the rounds 4 times at approximately 0° (A marking), 180° (B marking), 90° (C marking), and 270° (D marking) (so that the bullet hit the feed ramp at evenly distributed angles) using the slide release, then measured them.

I chambered all rounds four more times as above and measured again.





Notice that the COLs are actually getting a little longer in the group D cartridges. This may be due (in part) to peening the bullet nose and making it sharper. Not sure.



Afterwards I pulled the bullets. 1,2,3 are in group A. 4,5,6 are in group D. It took two decent whacks to pull the group D bullets with the impact puller. The group A bullets all came apart with one decent whack.





Conclusion:

In this test, a "much heavier than normal" crimp significantly increased the strength of the bullet-case connection. Group D bullets resisted setback and the COL actually increased slightly, the cause of which is uncertain. Group A bullets set back in a predictable fashion.

 

[Steve Koski]

Crimp die setting, looks the same for both A and D.



Mag loading technique, ABCD on top, in an attempt to hit all four sides of the bullet.



Pre-testing pictures:

 

[ImjinScout]

Hey nice data, thanks for posting, I would be curious as to why the increase in COL, that doesn't seem right to me, just could bee tolerances of the measuring device

 

[LiveLife]

X-Treme 115/124/135 gr 9mm bullets are sized at .355" (same as Rainier) unless you order 147 gr which come sized at .356"/.357".

If you are concerned about neck tension and bullet setback from multiple rechambering, you can consider using larger diameter Berry's bullets sized at .356" or PowerBond bullets sized at .3555".

I usually use .020" added to the diameter of the bullet for the taper crimp in semi-auto reloads.

 

[Steve Koski]

Scout: My calipers are accurate to .001". The increase in length is real.

bds: I only crimp the CRAP out of dummy rounds, intended to be chambered a bazillion times. I would never do it with normal ammo, that is intended to go in once and be fired. I suspect crimping super tight like that is not good for accuracy.

Koski

 

[LiveLife]

LOL, my first thought was "mushroom bullets"

 

[1SOW]

I use Berry's plated and have done crimp tests to pull the bullets and look for "damage to the plating" like your group D show.

A .356" Berry's crimped to .378" holds fimly and doesn't show that kind of damage to the plating. I have to look very closely to see any mark at the case mouth. Their 124gr HBRN TP (thick plating) behaved like a FMJ would with that crimp. I'm using the Lee seating and crimping die for my results.