So what's the right way to CRIMP?

[ed]

Pardon the silly question...
I've been reloading for ~2yrs. - mostly handgun (.38/.357, .44, .480, 9mm) and I can't find any information on the correct amount of crimp to apply.  I have seen examples of overcrimping (bullet deformation) and I know that undercrimping/not crimping at all can allow the bullet to move in the case, causing higher case pressure/cylinder lockup, etc.

How much does crimping affect overall pressure?  
I have some .357 loads that are loaded below published max data, but still have flattened primers.  I'm worried they could be crimped to much??

Any general guidelines for a good crimp?

I use a roll crimp on all revolver loads, taper on the 9mm.

Some insight from some experienced reloaders would be much appreciated.

[KN]

I don't think you can really have too much crimp. Not without damaging the case any way. As long as it looks good and uniform you should be all right. A heavy crimp will not cause preasure problems. A light crimp can cause inconsistent ignition with some powders though. As far as flattened primers go, when the round goes off the primer is blown back against the frame and then the case is pused back till it hits the frame causing the primer to be pushed back into the case flush with the case head. making it bassically flat. Don't try to determine preasure from the primer condition because 99% of the time a flat primer won't tell you any thing. Keep your loads within load book data and you should be just fine.  Hope this helps.  KN

[Sixgun]

ed

I crimp my reevolver ammo with a Lee carbide crimp die in a seperate operation.  If your cases are trimmed to the same length, you will get a consistant crimp each time.  With the Lee die you will not damage the case if you apply too heavy of a crimp and it sizes the loaded round so it will fit into your chambers, even if it does get a wrinkle somewhere in the reloading process.  This die gives a roll crimp instead of a taper crimp and they say you should not roll crimp ammo for auto pistols.  However, I have tried this die on my 9mm, with a very light crimp and it works fine in my 9mm pistol.

Sixgun