Got one a the 375 uppers from Tromix. Fit and finish is pretty good! They shipped it fast, couple a days and it was here. Put a light hand guard from Gibbz on it and am using my SW base for it. With scope an mag its just over 9 lbs. They have the dies for 375 there, so I got that with the upper. You can neck down 458's if you need to. I ordered the brass from SBR, save some work. No crimp on the dies so I may see if Lee cant make one. The rounds look like a pregnant 223. I loaded the first ones with 47 gr RE15 and a Sierra 200gr pro hunter. We'll see how they work. Tromix says any steel mag will work but the 450 Bushmater mags seem to keep the rounds centered better than 223 mags. I asked Tony how many of these are out there and he said he'd sold around 70 so far. Anyone else run across one yet?