So I took the Max10/31 to the range the other day and just for comparison sake I took my Max31a also. I shot a drum, coffin and Zmag S through each weapon and here are my casual observations. I had PS side folding stocks on both guns (I have a Lage fixed stock, but have not switched out yet) and I was shooting American Eagle 115gr ammo (with current rebate it is cheap). Both weapons functioned flawlessly without any malfunctions or FTF.
The Max10/31 is noticeably larger when you lay them beside each other on the bench. It is also a little heavier, but while shooting I did not really notice the difference. Both weapons pointed well and were very controllable. The cyclic rate on the Max10/31 is slower than on the Max31a. I did not have a timer with me, but it is noticeably slower. Group sizes at 25yds were very close to the same size both for short and long bursts. I did not try any SA accuracy comparisons because my M11a is FA only.
To me the ergonomics of the Max10/31 were slightly better than the Max31a (FYI, the Max10/31 was mounted on a Mac10-9). Of course I am 6'3" with long bony fingers so go figure the larger weapon would feel better in my hands. I don't think you could go wrong with either one.
Thanks Richard for bringing another excellent product to market.