I am relatively new to PCC please keep this in mind when reading. I started with the new Sig MPX and wanted to love it (and loved it for some time) but with 1 out of 50 FTF with factory ammo + much more complex to clean then a JP) I sold it... and bought the JP which has been super reliable and gives this proud of ownership feeling (it's a Mercedes amongst cars..)
Today I shot some 600 rounds (all 115 GECO factory at 150 PF) testing 3 buffer set ups for the JP 15-GMR. All shots double tap as fast as sights allowed looking for smallest group / fastest sight recovery at 12 meters (13 yards):
* MBX (yellow spring as supplied + blue spring which is softest)
* JP Short stroke 3 steel, 2 Tungsten
* JP Short Stroke 5 Tungsten
* JP 3 steel/ 2 tungsten : hardest perceived recoil, fast dot recovery, dot going up a bit and to the right, good group (<5 inch)
* JP 5 tungsten: softer feel compared to above but somehow a little bit slower feeling.. Group ok, slightly wider then the above
* MBX: softest as for recoil by far (really noticeable even if its only 9mm), group was little better then JP 3/2 system. But... Feeling was more ' sluggish', it just didn't feel right to me... Can't explain it better. And you need a lot of locktite to keep all together, some pieces came loose after only 100 rounds..
Overall: the way you grip the gun does more then the buffer system.
For now I stay with the 3 steel 2 tungsten JP system for feeling (and reliability).
A blitzkrieg system is underway as a new JP from a friend with the standard all steel buffer. So next comparison will come.