I haven't had the opportunity to shoot a 750 YET; but I remain hopeful. I have an older 742, and I have complete confidence in it. It ONLY shoots my handloads, and with 35 years of experience with Remi Semi and trombone rifles, I feel the platform gets a bad rep from shooters that don't really understand just what is required to make these rifles work.
Factory ammo is loaded with whatever powder they get by the railcar load. Burning rates vary, maintenance on personal rifles varies, and some guns simply won't shoot any ammo regardless because of whatever quirks the rifle has.
KEEP THE CHAMBER CLEAN! Ammo loaded with MEDIUM burning rate powders is best- nothing faster than 3031, and not slower than WW760/H414. Your favorite load with 4350 or 4831 MAY cause feeding problems!! If you are shooting a 760 or 7600, the slower powders may work OK- maybe not.
Magazines are 90% of the feeding problem. The lips have to position the top round properly for the bolt to pick it up when the action cycles. If they are bent down too far, the bolt misses the round partially. Better to have them too high than too low.
My rifle will shoot any bullet weight I feed it mainly because I've taken the time to develop ammo that meets the gas pressure requirements, and I small base size my brass to make sure the round sits on the bottom of the chamber when in battery.
Keep in mind that these rifles are meant to shoot one to four shots from a cold barrel. They are not designed for sustained fire like an AR or Garand!
I have a couple pointers as far as powder goes-
110 grain bullets, IMR 3031
125 to 130 grain, WW 748 or BLC2
150 grain, 748, BLC2, 4064, 4895, 4320, W760, H414
165 grain, W760, IMR 4064, 4320, H414
180 grain, W760, H414, IMR 4064
I haven't seen the need for any heavier bullet weights, so if you have to shoot a 200 or 220, try 4064.
DON"T try to hotrod the ammo; 48,000 cup is fine.
My old slushbox would go to Alaska with me if I had the dinero and time. I have no doubt that it would function in 20 below weather with daily maintenance and properly loaded ammo. CB.