[caz223]

I wouldn't use FC brass in ANYTHING.
I like win brass for .40, but whatever works....
According to my vague understanding of pressure and barrel length, longer barrel lengths INCREASE pressure. I found out the hard way when I used my hot loads that worked great in my 4 5/8" blackhawk, and used them in my 7 1/2" 657. Instant pressure signs. Flat primers, I mean FLAT. I decided to use gun specific loads for that application, and all my 7 1/2" guns get a different diet than my 4-6" guns. It seems that last few inches of barrel length really sent pressures up. That longer barrel put you over SAAMI standard pressures.
I personally wouldn't use the 12 grain load in a 5" barrel, there just too much that could go wrong. PLEASE sort your brass by headstamp and check for expansion. Use the brass that expands the least and you'll minimize the case failures, at least delay them.
With a 3.9 inch barsto, I prolly wouldn't hesitate to load it with the longshot hot loads, but I'd certainly make some changes in my loading process.
Like using virgin starline brass for your max loads.
Using a redding competition seater die. I just started using these, but they are AWESOME. They seat bullets straight, cause no bulges or ripples, seat bullets in undersized brass, extremely consistant OAL, and have a micrometer adjustment.
I recommend the Redding competition seater die wholeheartedly.
Instead of using a factory crimp die which can hide some of your problems, use a EGW undersize die. It sizes the brass down .001 smaller, and farther down. When used in conjunction with the redding competition seater die, it eliminates the need for the lee FC die. The lee FC die post sizes your brass. It also post sizes your bullet smaller inside your brass, reducing the neck tension, creating possible setback issues.
The LEE FC die serves no purpose (Other than crimping.) if you use the EGW undersize die and the Redding competition seater.
It was hard for me to give up the security blanket of a LEE FC die, but I now see the error of my ways.
You don't really need to give up the LEE FC die if you don't want to, as if you use the U die and the comp seater, the brass is sized smaller, and the bullet is square, so it really can't hurt much, but it might still be post-sizing a tiny bit, and it really doesn't need to....
Incidentally, I've had very few case failures over the years, they have been limited to a couple of headstamps. I remember factory blazer ammo in 9mm splitting from bottom to top, I remember FC in .40 showing incipient case head damage after their first firing, I saved all my failed brass over the years to remind me what to look for, and if I could only find it.... I know it's in a little tupperware container, but during the last move I must have misplaced it.