I haven't bought any in a while. I bought a couple of boxes of 308/150's and 30-06/165's right after they were introduced. Neither matched speed claims, but the 308 was close and faster than I could duplicate with hand loads. Accuracy was acceptable, I'd hunt with it. My hand loads are a little more accurate, but probably not enough to matter.
I was able to match the speeds I got with their 30-06 loads with my hand loads, and with much better accuracy. I've noted that they have since modified the speed claims on their 30-06 ammo. And I did get a notice that the 30-06 ammo I bought had been recalled. I'd already shot it by the time I got the recall notice. Don't know if that was the reason for poor performance or not.
Will 50fps make that much difference?
That is 50 fps at the muzzle with a different bullet. At 200 yards a GMX with a 50 fps head start will be closer to 200 fps faster than a Partition.
