Crimp

[Long Gun]

A lot on the net about bullet crimping. I’ve crimped my latest batch of rounds as even when sized I still get a few cases that are too loose to firmly hold the bullet. Remains to be seen how these perform.

 What are your real world experiences with crimping, if any?

[Strangely Brown]

In a word, uniformity.

I found group sizes tightened up with a "light" crimp.

[DaveT]

Are we talking pistol cartridges or bottleneck ?

If the latter then I disagree about crimping.......look to your neck tension ....it should hold a bullet perfectly of its .001" - .004" with no need to add a crimp.

[Long Gun]

Talking rifle Ammo. I neck size, make sure each case can’t have a bullet pushed in.

 Then when I’m seating the bullets later on I always always find a couple where the bullet can be pushed in and out by hand. Infuriating.

 What’s the consensus on damaging bullets with crimp?

[Long Gun]

1 hour ago, Strangely Brown said:

In a word, uniformity.

I found group sizes tightened up with a "light" crimp.

Indeed, I’m hoping that a light crimp on all my rounds all of the time will go to keeping consistency across my Ammo.

[DaveT]

If you can push bullets in and out by hand then something is wrong with your sizing and a crimp will only serve to disguise it.

Measure a loaded round that you are happy with by using calipers across the neck......obviously this gives you 2x neck wall thickness plus the bullet diameter.

If your neck sizer is a bushing type then make sure that the bush is at least  .002"  LESS than the above measure.

If it IS but you are still getting loose seating then suspect the bush is wrongly marked OR the brass is too work-hardened to retain the sizing.

If you have a standard neck sizer then after sizing but before seating a new bullet measure across the neck , subtract 2 x neck wall thickness ( you will need a ball micrometer not standard calipers for this) ....the result is the inside diameter of the neck and  it should be  .001" or more to provide adequate neck tension to hold a bullet. 

If the measure is the same diameter as your bullet or only marginally less then you clearly have a die issue .....expander ball too big?

 

[DaveT]

Sorry meant to say the inside diameter measure should be AT LEAST .001" LESS than bullet diameter.

[bradders]

1 hour ago, Long Gun said:

 What’s the consensus on damaging bullets with crimp?

They're getting shoved down a barrel full of lands and grooves at 1900mph and spinning around 240,000rpm

A crimp isn't worth worrying about

[Andrew]

4 minutes ago, bradders said:

They're getting shoved down a barrel full of lands and grooves at 1900mph and spinning around 240,000rpm

A crimp isn't worth worrying about

Exactly my answer when people ask me about bullet damage!

I crimp everything with a Lee Factory Crimp Die and if Lee doesn't make it for the chambering I'm loading for, I hire them to make it. I get smaller groups and lower ES and SD. Do not use the 'roll crimp' that comes with some seating dies; the Factory Crimp Die is the only one that gets the job done when used correctly. To the OP's post: If your bullets are still loose in the necks, know that this is nothing caused by the crimp and probably won't be cured by the crimp. You've got a problem someplace.~Andrew

[Long Gun]

Good info so far. Thanks all.