I worked up some loads last year for the father-in-laws 750 using 225 partitions, remington brass, and RL15. I used CCI 250 mag primers, and found that it liked full power loads the best, (60 grain range) for 1-1.5" groups. However, these loads would have the primers all pushed out of the case. Case expansion showed they were okay, but I couldn't figure out why the primers were doing that. This was using FL sized brass. I switched to 210M primers, and the issue went away, however, the accuracy was not as good (2-2.5" groups). I believe I was getting a pressure spike with the 250's. The thing is that the FPS did not change when going from the magnum primers to the std. I also found that seating depth improved the groups, changing them .005" at a time.
The best shooting loads with the CCI 250's at the highest charges also did not cycle the best. The bolt would catch the mouth of the case before it would clear, jamming in the action, or creasing the neck. Lower power loads cycled without these issues, but were less accurate. I settled on the loads which cycled every time, not the most accurate. They were still 2600 fps in the 22" barrel, and ES of 5!
If shooting strictly moose, elk, bear, and the odd deer, I would load 250 partitions. Here is a recommendation I was given.
In the good old Whelen. The 225 grain Partition is one of the poorer performers of the Partition line due to its extremely low SD. If it hits major bone on game weighing around 600kg or 1300lb, it will tumble and lose its rear core, time and time again. Forget about velocity and go for SD. Very few people understand just how effective the .358’s can be and just how much they differ from other bores. As an an example, the .308 produces a great deal of hydrostatic shock on medium game at impact velocities above 2600fps, while the 35 does the same- way down at 2200fps. The .35 has no trouble imparting energy as long as the velocity is reasonable so all you have to do is try to keep impact velocities above 1800fps to promote wide wounding. The 250 grain Partition driven at 2400fps will keep you out of mischief out to 325 yards on larger deer and Moose. My other favourite is the Woodleigh round nose, it is very emphatic for sure. Things to note about the Woodleigh are that the RN expands a lot faster than its pointed counterpart and tends to dump a lot more energy (actually, the same goes if you compare the Hornady SP and RN on deer). The Pointed (PP) bullet is a very deep penetrator but is not the be all and end all.
I believe the Canadian rep is out of most stock at the moment but I bet he has some .35 cal bullets somewhere. I have used the 225gr RN woodleigh on wild cattle. It is quite acceptable but I do prefer more SD. My neighbour (farmer) uses the .35 Whelen on everything, the way most people use a .270. I gave him my test rifle after he fell for it. Can’t believe he has the 200 grain Hornady zeroed and set up for 300-400 yard shooting of goats in his pine plantation, the 225gr GK for deer and pigs, a swag of my old obsolete 250 grain Barnes X bullets for wild cattle. I used to use the Whelen out to 250 yards, never thought I would see one set up for 0 to 400 yard shooting. Bullet drop is two feet from his zero which he rightly describes as being “much like a .308”. If you really like this caliber for Moose, perhaps also consider a bolt action in the future as a long term proposition- either the Whelen or .358 Norma (just use 338 Win mag brass). There are a host of good donor actions for such a project out there, cheap actions like the Howa stainless (good in the snow) etc. A good, accurate bolt action .358 can help stretch range potential so that you don’t feel handicapped when you break out of the Alders and see your quarry across a valley 250-300 yards away.
Should mention, if you want to try the Woodleigh bullets and can’t get them from your rep, you can purchase Woodleigh bullets at a good price from Queensland Gun Exchange in Australia. They will sort the paper work and freight.