Blacklab, any time a simi auto malfunctions the magazine should be the first thing checked, asuming the gun isn't plain filthy to begin with!
Their have been more 1911's cursed and hated because of crappy mags than any other single problem, and this is sad because it's so easy to fix.
Another thing I would watch for is the sizing die, as I always use a RCBS small base resizing die whenever reloading for a simi auto rifle.