Generally, commercial +P ammo wil not put any excessive strain on a modern handgun when used for function testing and defensive purposes. Shooting +P all the time at the range might accelerate the wear on a gun, but nobody expects +P ammo to be shot all the time, that is what your standard plinking ammo is for.I just got my Springfield GI.45 Micro a couple of months ago. Still trying to decide on which ammo to use with mine also. So far it has eaten everything I've put though it but did have some problems for the first 300 rounds. So far with all the different ammo I've put through it (including 185, 200 and 230), it seems to like the Remington Golden Sabers in 230 over the Federal Hydrashoks in 185 or 230. But there are still a few types I want to try out in it. I haven't used Hornady XTP, Speer Gold Dot or the MagTech yet. Have heard good things about them for the 3" guns and need to try them out also. I have been told by many people that the little 3" can be very fickle on ammo, but so far haven't had too many problems with any. In speaking to Springfield on a difference issue, I brought up using +p ammo in the Micro and was told very energetically not to use it in the short barreled guns. It all had to do with cycle rate and was told that it puts a huge strain on the double spring set up that the Micro has, but not sure what the Defender has. BTW, great looking Defender!