I owned a couple and they were reliable with ammo that was somewhere near the length of a ball round. Mine didn't like short 95 grain HP ammo. I would expect the 59 to work fine with any 115 gr. or heavier bullet. Most any modern JHP would be OK. Sources I respect say the CorBon DPX 115 gr. +P is the best defensive round in 9mm, but there are lots of other good loads.. However, the 59 was made prior to +P and +P+ ammo availability and if it was mine, I would use a standard pressure 115 gr. load like the new Hornady Critical Defense load or the Speer Gold Dot.
They are nice pistols but a bit more finicky about ammo than later guns.
Edited by wildhobbybobby (01/27/10)
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