Which of the two versions the Eley or the Jeffrey would you prefere and why?

As far as I understand the Jeffrey version uses .488” 500 grains bullets and the Eley version uses .483” 480 grains bullets?

Are they both regulated for 2150 fps or is the also variation between the versions in this concern? John Taylor states that the Jeffrey version only delivers 2000 fps?

Is the case the same or has the Jeffrey version reinforcements?

Please let me know what you know and think of the two versions.

DvK