I have loaded for the 350 Rem Mag for years. Mine is in a pre-64 model 70 and a custom stock. My round is out seated and therefore, holds more powder and will go a little faster than a rifle that has the 2.8 OAL. If you want my data let me know. It is a great round. My best friend sold his first 338 Win. Mag. after we did a shoot off. My 250 gr. Partition went 70f/s faster than his and with a shorter barre.

I've got a Remington 673, so am limited to the 2.80" COAL.

I'm still working on the ideal load. Right now, the Nosler 225 partition, over a max (per Nosler) load of IMR 4320 has given the best accuracy (note that the same bullet with 748 was not impressive). I was very surprised to note that the CCI magnum primer provided substantially better accuracy than the standards, something that I didn't expect with the not-very-large .350 case and 4320. However, I loaded up a couple of test batches on different days to make sure that the first time wasn't a fluke, and even shot groups alternating shots/targets between loads using the two primers, and the results stood up.

My next experiment will be the 225 Barnes TSX, which I hope will take accuracy up a notch or two.

Mine is built on a 98, so I'm in the same situation as lb404. I've chronographed my loads at 2615 fps avg velocity with a 250 gr Speer, but I wouldn't expect this in a rifle limited to 2.8". You can always lengthen the magazine box and do a little throating to allow you to seat the bullte out a little further. Basically, it does pretty much anything the 338 does with similar bullet weights. FWIW - dan

In my Rem 600 in 350 RM i use:

IMR 4320 @ 56.0
250 Speer Spitzer
Fed 210GM primer
Rem Cases

same load for the 35 Whelen also I don't rec a prem bullets because of the lower vel of the 350 Rem mag and Whel.