Well, today's shooting session invloved five different guns and my chronograph. All went very well and one of the tests was the Barnes new MRX (It should be called the MR$$$ bullet). Twenty bullets retail for about $25.00.
I used a very well proven rifle an old 30-06 Dakota model 97 with 24" super smooth barrel. This rifle will typically send 180 grain bullets at 2800 + fps with a relatively mild load. I started with a proven powder, brass, primer combination and here are the results. The Partition load is a test load for reference. It had been used before and I included both old and new ammo loaded with this combo to compare with the MRX load.
All Loads were with Lapua brass and Federal-210M (match) primer. Velocities are average of five shots, 15' from the muzzle. All bullets were seated .025" off the lands. Cartridge OAL was 3.305"
Nosler 180 grain partition spitzer.
(old load) Fired last year.
H4350 56.0 grs. 2816 fps, sd=13
(new load) Fired today.
H4350 56.0 grs. 2820 fps, sd=11
180 grain MRX
H4350 54.0 grs. 2728 fps sd=12
H4350 55.0 grs. 2774 fps sd=10
H4350 56.0 grs. 2802 fps sd=15
The 55.0 grain load was shot for accuracy with five shots going into .8" in two minutes, from the sand bags. The last five of 25 shots. I only had 20 MRX bullets and loaded 10 of the middle load, guessing it would be the best performer. Judging by the sd numbers it was. Another hint here is the 46 fps gain from 54 to 55 grains and only 28 fps gain from 55 to 56 grains, the max load here is the 56.0 grains. I would now try 55.5 grains and it would likely be the best. There were no pressure signs detected with the 56.0 grain load but I'm at the knee of the pressure vs velocity curve as evidenced by the short gain in velocity with the last one grain increase.
This rifle has two very obvious talents; It is fast, very fast (due to the very smooth barrel) and it is very accurate. (I did not shoot the partition load on target today but it is truly a .5 MOA load.) It also doesn't care whose bullet it is or if it's barrel is very warm. I could touch the barrel to my face after the fifth shot, it was not hot.
I don't have TSX data to compare this with so make your own guess. The MRX is something other than lead in the shank and it has the TSX grooves around the bullet.
Just a little loading tip for your shooting pleasure.