So after much messsing this weekend I noticed half my mags won't feed right part feed and insert smooth and the others are very tight and will not cycle. How can I tell if they are just bad or the inch/metric difference

If your rifle is metric, it will not accept inch mags at all.

Otherwise, check the mag bodies for squished or dented sides, that might pinch or drag on the follower travel.

Check mag feed lips ontop for flattening. most of the bind will be at the front portion.

If nothing, take them apart for cleaning. maybe replace the springs ?

I don't have any information on your rifle, but more generally there are some Century FALs which are basically Inch but the mag well is too tight to accept Inch mags very well but which will accept most Metric mags without a problem.  So these rifles have all of the marks of an Inch FAL but it is best to use Metric mags in them.  I have one of these.  I am putting aside any feeding problems which may occur using the Metric mags in these Century FALs.

Drakejake

Drakejake,

Not to hijack the thread but did your inch pattern century actually have an inch front end and front sight?  

I was looking to buy one but have heard of them with inch rear sights and metric front ends that won't work together (puts bullet impact way off)

SoS

My FAL is consistently Inch, so far as I can tell.  I have been told that it is probably an Australian kit on the Century receiver.  The receiver is also Inch but has the tight mag well I described.  By the way, this is a Unibrow that wouldn't feed consistently with any mag (I have several dozen).  But by bending the mag feed lips up a bit, I have been able to make it work.

Drakejake