Gday fellas,its a long time since i have been here.I lost my computer to a bug and lost all my contacts.I have a glock question for you.I bought a KKM precision barrel for a glcok 21.Its number is G21H1C,has a compensator on the end.I am not sure what polygon rifling looks like,so when i slugged the barrel it had hardly any rifling marks on the lead slug.Is this a polygon barrel and should i only use jacketed projectiles in it?Thanks for your time.