Could I use once fired Glock Brass in my STI 10MM without any problems, or should I keep the Glock brass and STI brass separated?
when in doubt get a case gauge. I don't seperate my brass by pistol. Two glocks, two witness and a Para P16/10mm.
When you resize it the sizing die should take any bulge from the brass left behind from the Glock bulge/smile. I keep my brass separate for my bolt guns but everything else gets whatever I've got sitting around for it.
http://10mm-firearms.com/reloading-10mm-ammo/pass-thru-sizing-using-lee-fcd/
Pass-Through sizing reaches the areas not touched by conventional dies/shell holders or shell plates. I pass through size using the LEE FCD with the guts removed and a bullet sizing push pin. See link posted above...
I do all 10mm / 40S&W / 357Sig / 9x25 Dillon with the 10mm/40S&W FCD. I also do 45ACP and 380ACP with their appropriate FCD dies, 9mm takes a different FCD to perform a Pass-Through using a 9x18mm (9mm Makarov) FCD to perform that pass through...
Thanks for the advise, I ordered both the Lee and the Reading, couldn't make my mind up, so I though I would try both. The Reading was expensive but I shoot my 10mm the most.