You run a nice site there.
I'd like to see a comparision similiar to what the U.S. Army did in a training film back in WWII when they compared U.S. vs. German SMG's. They fired each weapon at a specific target and then compared the hits.
The target they used was two silhouette targets side by side. It would be the equivilant of two IDPA/ISPC targets next to each other and touching. They used a clean target set for each gun.
For a LMG change the distance back to 100 yards or further, instead of the 25 or 50 yards they used in the training film.
Load the same number of rounds in each magazine. The idea isn't to see which had the higher mag capacity, but which would give the greatest number of hits per shots fired.