If you're reloading Glock-fired brass and then shooting it in a Glock it makes no difference, but it makes a big difference in something with a tight chamber.
The idea that Glock barrels are unsupported is 100% false. They're supported roughly as much as any other ramped barrel out there, but the chamber mouth is slightly larger, which allows the case to expand a small amount more. It will still prevent a case failure/rupture just like any other supported barrel, which is all that the supported area does aside from smoother feeding.
The Lee FCD is considered by many expert reloaders to be a BAD idea. It squeezes the entire case, which can actually reduce bullet pull (neck tension) since it squeezes below the bullet and that can lead to bullet setback, less consistent velocity, etc, etc, etc. It does a decent job of hiding problems, but it really doesn't fix them.
For cases that have been fired in larger chambers a U-die combined with a good seating die (nothing tops the Redding Comp Seating die) and good taper crimp die is the only real way to get rid of the problem and not hide it. I've added a shell holders cut down to get the very last little bit of the case above the extractor groove, but that's going above and beyond. R,
Thanks! I have 2 sets of bras about 1/2 fired from a Glock 22 and 1/2 from a HK Compact. Will run them thru the Dillon sizer and see how they turn out.
If needed will try the Lee die after for any not SAMMI sizing...
Thanks!
Wayne