I have a Global Trades SSR-85B and the magwell is kind of tight with certain mags and not just the Bulgy Waffles but Polish Synthetics and even some E.German Steel and Hungarian 20rds.
I have to force mags in and pull them out.
BTW it's already been back to Global...TWICE!

Which way is it tight? Width or length?  

If it's width, you could lightly and carefully dremel the each side and touch it up with some Alumahyde or something similar.  

If that doesn't work, I'd reccomend sending it to someone besides Global for an unbiased assesment and repairs.  

The SSR85B is a sweet rifle though, so I would hang onto it, tight magwell or not.  

Yeah I figured maybe an emery cloth just on the magwell/receiver sides lightly.
When I first got the rifle Mags could not even insert(so mouch for QC).
So to remedy they must have dremeled the two lower rails and the two trunion rivets,left all the shavings and bare metal visible then sent it back.(What a nightmare!)
Also the center support rivet was totally screwed up.
Like I said some mags fit well and others need a little persuasion.
I bought it cause I wanted an AKM pattern AK it is nice but it'sa little annoying.
Since I never fired it when it first went back I feel they should hve given me a New Rifle.
Oh well.....

Does your rifle have the FEG receiver or the other one they were using ?
I have a FEG SSR85B as well and I absolutly love it !!

It's an FEG SK100 which from what I have read were not fully finished.There was an admission on Global's part and posted on "that other website" that certain machining steps like riveting were pieced out and were not being performed correctly.