I've owned my A1 for 8 years and the first barrel I got was a 300WM, I've been using those mags with zero issues and they are interchangeable with the 338NM.
yeah completely "normal" . make sure you clean the channel where the Striker runs through. the skinny 4-6mm channel.
I like to run Hornady oneshot case lube in the action , seems to slicken it up