In a discussion on the PF-9 list about whether to shoot steel or aluminum cased ammo, I called KT and was told........ "We RECOMMEND no steel or aluminum cased ammo. " Notice, it's only a recommendation and that was from non technical people. This was fun. First I heard "the no steel, or aluminum ammo is in your user guide". When I pointed out that it was not, I got "it's not SAMMI (hope I got that right) standard." When I asked how they knew that, I was transferred to Customer Service. I don't recall the CS guys name - but all he could do is quote the party line. Seems the reason for brass only is customers sending weapons in for repair and reporting they'd been shooting steel or aluminum cased. When I asked for hard evidence or the written opinion of an ordnance engineer, I was told, "I don't have time to sit here and discuss it with you." xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx (edited) I strongly suspect the reason they advise only a bit of +P and no reloaded is the recoil system. These things have a simple spring recoil system and using ammunition stronger than standard will cause the moving parts to beat themselves against the nonmoving parts. So brass, steel or aluminum - help yourself. It's your pistol.