Too much crimp

[David2011]

Michael,

The spec on the neck diameter is .380". Measure your case necks and adjust the taper crimp die to give that size. I measure a hair behind the mouth to avoid any burr on the mouth that would make the measurement inaccurate. Seat a couple of bullets and pull them to see if they're damaged.

Another thought- don't flare the necks any more than necessary to get the bullets started into the mouths. That will help maintain proper neck tension.

David

[michael.birdsley]

Michael,

The spec on the neck diameter is .380". Measure your case necks and adjust the taper crimp die to give that size. I measure a hair behind the mouth to avoid any burr on the mouth that would make the measurement inaccurate. Seat a couple of bullets and pull them to see if they're damaged.

Another thought- don't flare the necks any more than necessary to get the bullets started into the mouths. That will help maintain proper neck tension.

David

So when looking at the print. The spec for any cartridge at the case mouth is what I should crimp too? After seating a 9mm round my nominal case diameter is .377-.3765. When I crimp it only takes it to .376 some rounds will be 375 but, dosent look like I am crushing the bullet. Is there a SAAMI book to get +- allowed on the spec of .380. So I should flair the case more untill it is .380?

[mongoose33]

I've shot a lot of plated bullets and while the ideal is to just straighten the case wall back to parallel, a little bit of dent in the side of the bullet doesn't, in my experience, change much.

Unless you have evidence of extreme inaccuracy or see pieces of plating flying off, what I saw in the pic is ok. I would back off a bit, but I'd shoot those and expect them to perform.

[michael.birdsley]

This looks exactly like a profile crimp. It is a combo of a tapered and roll crimp. It is used sometimes for ammo that is going to be used in full auto and semi auto use. Oh and sometimes in NON Lead bullet use.
Why would this type of crimp be used? It supposedly does not allow bullet jump or movement such as a tapered crimp would , for example when you jack a round into the chamber, then remove it later. Next day you rack it into the chamber again. This repeated action causes the bullet to keep going deeper into the case. I have seen this mostly with 45 ACP ammo. Standard ammo, this would not be so bad, but some Plus P ammo would not be good. Never heard of anyone blowing themselves up from this, but some LE guys have commented about that first round being more powerful, and throwing their POI off. This was the end result of them racking the slide and keeping that one bullet on top of the magazine. Simple solution is to rotate ammo.
But let me point out that this looks like the machine or Press that was doing this, was out of adjustment, and was crimping too much. I can't post photos here, but if I could, I would show you that the same thing ( or look ) on a twenty caliber bullet. The die was out of adjustment and looked this bad or worse. And the same thing happens to groups. There is not groups but patterns.

I think this is what I was doing to the cases. Roll crimping and than tapper crimping on accident my fault. Tried sizing the crimp to .380 but, it wouldn't flatten the case mouth out, acurracy suffered. I don't think I was flaring the case enough. Best accuracy is crimping about .376. Checked my factory ammo and it all runs about .376-.378. But, now I'm getting fail to ejects with me reloads so I'm going to try bumping up a grain or two.

[philzilla]

That pic is great