The desired 10mm crimp

[Kenk]

So what would be a desired crimp on say, a 180gr XTP 10mm?, I use a standalone hornady crimp die, and always make two final checks before completing a batch of ammo;
make sure the case has not become deformed due to over crimping, and do the standard plunk test in my LE Wilson case gauge. I have never measured my crimps, but is something I?d like to start doing. Also, not measuring has never caused me any issues, but would like to start
Thanks

Ken

[nhyrum]

You don't need to crimp a ton, you want a thou or two of taper crimp. Really, just enough to bring the case mouth back to spec. You don't need or want a ton of crimp

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[Kenk]

Thanks, but if you were to take a measurement, what are we looking at?

[Kenk]

So I just measured one of my factory Underwood 165gr bounded rd?s, and came up with .421, does that sound about right, and is that what I?m looking for in a standard 10mm crimp?
Thanks

[nhyrum]

Will, saami spec for the case mouth is .423, so, I'd go a thou, maybe two max, under that, at the mouth. 421 should be fine, but it's too much for what I'd do. I think people crimp far too hard. Just about everyone crimps 44 Magnum WAY harder than I crimp my 454 casull, and I load it pretty hot. Even there I'm at about 2 thou crimp. Never had any bullet displacement there

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[Kenk]

Thanks nhyrum!

[jmm701]

I usually crimp between .420" and .422" and never had any issues.

[sqlbullet]

I flatten the flair, usually that is about .423.  If I am compressing AA#9 I might go a bit tighter.

[Kenk]

Thanks folks, flattening the flair enough to look and plunk correctly has been my main focus

[CERJ]

Looking at the SAAMI for 10 mm (and if I?m reading it correctly) the case at the mouth with no projectile = .424
With a projectile = .423
Last time I crimped I went to .421

[gnappi]

In my revolver loads I crimp pretty hard but to where they still pass the plunk test. After losing what I thought was a good crimp and a bullet losing its crimp and locking up the cylinder. I feel better with more crimp than less.

One problem overall is having mixed head stamp brass with different numbers of firings. Some are shorter than others (up to .020") and the shorter ones can more readily lose a crimp on full power loads. So when setting up my crimp die I set for the shortest sized case I find, and make sure the longest still plunks.

After setting up once for that I can forget the crimp op totally.

Oh, I use setscrew locking rings on my dies in my Dillon presses, the old style they used to have do not cut it here and I threw them out.

[Kenk]

Thanks Gary!

[The_Shadow]

Having documented many 10mm over the years, I can say that the best tapered crimps as measured have been as follows:

Jacketed Bullets are 0.400":  0.4215" - 0.4220" as measured that the very edge of the case...  Underwood has held to this standard with their products.

Plated Bullets which are 0.400" to 0.401" and even 0.402": 0.4220" - 0.4230"  (Be careful as thinly plated bullets can be damaged if over crimped. Such as scaring or cutting the plated jacket.)

Cast Bullets which are 0.4015" to 0.4020":  0.4220" - 0.4230"  (Bullet size is everything when shooting lead alloy that is traditional lubed) (Never use the LEE FCD as the die can squeeze the bullet to a smaller size and that can lead to leading or loose fitting.)

[Kenk]

Thanks Wade, very helpful info

[RickShooster]

So what would be a desired crimp on say, a 180gr XTP 10mm?, I use a standalone hornady crimp die, and always make two final checks before completing a batch of ammo;
make sure the case has not become deformed due to over crimping, and do the standard plunk test in my LE Wilson case gauge. I have never measured my crimps, but is something I?d like to start doing. Also, not measuring has never caused me any issues, but would like to start
Thanks

Ken

It takes a little while to do the extra step, but I plunk test every round with my 10mm.   I have a Double Diamond barrel that was pretty tight chambered, I polished it  a bit and it's still pretty tight but now I have no feeding or malfunction problems with all rounds passing plunk test with a moderate crimp around .422- .423". The last thing you want is a jammed, stuck round partway  in the chamber when things go dicey nor embarrassment at the range.   Factory ammo is non-existent around here, and it's ridiculously expensive to order, so I plunk test  every round and I inspect powder level in the case every round before seating a bullet.  You don't need an excessive crimp, just enough to so the rounds plunk in and fall right out.  If they stick at all, it's not enough.