well i got a friend of mine to inspect them and they most definately aren't aluminum, which brings me to the same conclusion as Karl. ok, so upon closer inspection, the catch wans't [i]fully[/i] engaging with this particular mag. it engages enough to where you can't pull out the mag (unless you use an unrealistic amount of force) but the catch dosen't get as close to flush as it does with my other mags; so I'll now begin filing.
these don't seem HEAVY, but then again I haven't (knowingly) handled USGIs, so i can't compare.
at 14.95 a piece they seemed like a good deal.. for 2 out of three to work, and only a little extra work to do on the 3rd, that dosen't seem like a bad deal.. not only that but these mags look great!! i think i'll buy more of these sa80s (or at least thats what I'll say until I buy some USGIs probably [rolleyes]) go figure..
thank you guys for all the help, once I get through filing I'll let you know if it worked.
edited to add: also, one of these has a tight fit in the magwell, is that of comon symptom of SA80s??
edited again: well I think it worked, the mag catch engages way more than it used to. I guess I'll have to try it at the range to see if it really worked.. thanks again..