Has anyone had trouble using 30 round aluminum M16 or 100 round C-Mag magazines in a SIG 516?

Went shooting with a freind and it works fine with plastic SIG 30 rounders but not the other two.

The fingers that hold the ctg case in the magazine are quite a bit shorter on the plastic SIG magazines than the M16 pattern.

The rifle is not especially accurate either. Nice fore end and flash lite pistol grip however. (And magazines).

Any observations?

Andy

I have been shooting one on duty for the past three years and have no problems with any quality ar-15 mag that the department has issued and as for the accuarcy it is as good or better than the general run of rifles issued. RNB