I am going to test four different types of two different manufacturers' .223 Russian ammo in my POF P-415 upper. I will test the following ammo: Wolf 55 grain FMJ, Silver Bear Silver Bear .223 62grn HP Wolf Military Classic .223 55grn FMJ Brown Bear .223 55grn FMJ I plan on firing 40 rounds of each. Much like wine tasting, I want to make sure that my upper has a "clean pallet" for each flavor of ammo. I want to know what steps I can take between firing each type of ammo to insure a "fresh start", and be able to accurately note/judge each type of ammo. What I'm trying to see is which type of ammo will feed reliably in this POF upper. I had several stuck cases using Tula 62 grain HP. Thanks!