I have two. Ordered a reamer with Sammi specs when it first came out. Made a SA Ruger with McMillan Ultralight stock into the 338 RCM with a 22 inch #2 Lilja SS barrel. Used 225 gr accubonds and RL-17 @ 2750 fps to kill two cow elk.
At one point I seated some 300 gr Sierra bullets for single shot to see how they performed. At 200 yds I had some very tight groups as I worked up the load. That got me thinking of a second 338 RCM with a slight change to the chamber. I sent an tired 30" #7 SS profile barrel which had a Mark X LA reciever to Danny Pederson to have it rebored from 7mm to 338. At same time I shipped the reamer with a dummy round and requested the throat be lengthened for the longer magazine. Had excellent results.
When Berger came out with their 300 gr match hybrid, I switched to that bullet. Mild recoil with this 13 rifle which is in a Joel Russo laminate stock. With such mild powder charges of 54.5 gr of RL-17 velocity 2455 fps the barrel slowly gets warm and throat wear is minimal.
I took it out once on a coues wt hunt. Put that bullet through a deer that was bedded at just under 400 yds. It went in near leading shoulder and exited near offside hip. Little meat damage. The high BC of that 300 gr Berger minimizes drift and it packs a great deal of energy with 3000 ft/lb at just under 450 yds.
I read here that Broz used that 300 gr Berger on quite a few animals at LR. I quote:
"bedded cow at 816 yards.
Impact velocity was 1975 fps. Cow was slightly facing away. Entrance was in the crease behind the near shoulder. Exit was far shoulder. I was kind of surprised that the exit was only 1 1/2" or so. But this exit is deceiving. Note the bone fragments on the hair around the hole. Inside was total destruction and the exit shoulder was a loss. Elk died quick and clean. I am pleased."
I decided to have the SA mag box lengthened to 3.1" for a useable OAL of 3.050".
Worked up a load for the 300 gr Berger that fits and feeds from magazine. Ended up with: 54 gr of RL-17 fed 210 standard primer 2349 fps. Took it along on a bull hunt a few years ago for stalking the wooded slopes. Ended up not using it but did get a bull with a different rifle.
At 8000 ft for elk that slow heavy bullet in the SA Ruger retains energy well with 3000 ft/lb at 375 yds and if I used Broz's low impact velocity of 1975 fps as a minimum velocity for good expansion, the rifle is good out to a bit over 550 yds which is more than I would shoot at an elk. To date I have taken 27 elk and none were shots more than 300 yds.
While Hornady brass is a scarce these days it can be found. I suppose the 6.5 version could be necked up. I see ADG has 6.5 PRC available.
Here is the SA Ruger "tanger"
The heavy long throated 338 RCM: