9mm crimp question

[MilkMyDuds]

I noticed that some headstamp brass do not even require crimp die to pass case & chamber gauge.

I made sure my seating die (RCBS) is turned way up so it does not even touch the brass, so definitely no crimping on the seating station.

My expander die is the Mr. Bullet Feeder one, and the bell is pretty obvious.

Supposedly these particular headstamp brass walls are really thin, FC for example, but when I put the flared brass (after dumping out the powder) it would fail case & chamber gauge. My question is, how could the seating process (without any crimping) remove the flare?

[GrumpyOne]

My guess is that the seat die is removing some of the bell/flair or the case mouth.

[Hi-Power Jack]

^^^ What Grumpy said.

A cartridge that is belled will NOT enter your gun's chamber - you must be

losing the bell somewhere.

But, if it functions and there's no bullet set back, you're good to go.

[MilkMyDuds]

It's just strange that this only happens for certain headstamps, but not all. FC does not require crimp, but WIN, RP etc. all require crimp.

[GrumpyOne]

Brass has a memory, it springs back to whatever shape it had before, to an extent. With the FC brass being thinner, it does not have the memory of the Win, R&P brass, etc.

[Hi-Power Jack]

FC does not require crimp, but WIN, RP etc. all require crimp.

Not really a "crimp" but merely removing the bell - I'd remove the bell on ALL of

them - you've got a progressive - go for it.

[goldfieldshooter]

If it has the 'bell' before it goes in the bullet seating die and it doesn't when it comes out; then it must be the seating die ! They run close tolerances in the seating die and it must be enough to swage ( for want of a better word) the bell from the case mouth.