How much case mouth flair?

[Mwsenoj]

I am using straight nuclear medicine containers for my boolits and I am just getting to loading with them. How much flair are you using on your 40s&w? I have it set around .431

[paul h]

Flare the cases just enough so you aren't shaving lead, and no more. Any more flare than needed will shorten the life of your brass. I've never measured the dia of the flared section, I just keep tweaking the flare die until I'm happy with the setting.

[detox]

I also chamfer inside edge of case mouth to prevent shaving.

[ShooterAZ]

Yes, just enough for the base of the boolit to enter the case mouth completely, don't over do it. And remember when crimping to only remove the bell...no more than that.

[Tatume]

To set the die use a plain based bullet as a gauge. Put in a bit of flare, and attempt to stick the bullet in the case with your fingers. If it will not enter add a little bit more flare. When you can stick the bullet into the case just enough that you can release the bullet and it will stay in the case, with the case held sideways, you have enough flare. Any less will shave bullet bases. Any more is too much.

[Ed_Shot]

Totally agree with all the above. The other factor that affects your flare is case length. I recommend that you pick 25 or so of your 40 SW cases at random and measure them. Pick the short ones to use to adjust your flare die. I personally use a case that measures .840 to set my Lyman M die.

[fredj338]

All of the above. I have never measured, isn't that helpful if using mixed brass, so I just adjust to allow the bullet to sit on top of the case mouth & not shave the base.