Scenar are great rounds. I have had a few rifle that didn’t like them thou and wouldnt hold groups very well. I would try them out before buying in bulk. Also like said above the price is an issue for me.
I prefer the 300 WSM. I have shot accurately out to 2200 yards (probably would do much damage out at the range but the cartridge has the capability. 1500 no problem on a deer.
I learned early in this sport that it is better to spend a little more up front and get the best optic that you can. I would save up for the gen II razor like said by others in this thread.
If you did the loading port yourself you may have left to much material and are not able insert the shell past the catch. Like said above you need to pass your thumb past the port. It really just takes practice.