You're fine. It's long for the reason RL 338 stated.
Do some reading on reloading for the 300 WM. It has a belt obviously to headspace off of, but doesn't really need it. Only has the belt because it was carried over from the H & H cartridge it came from, that needed the belt because of it's low angled shoulder. You can set your dies for minimal shoulder set back just like a standard case that headspaces off the shoulder.
I only neck size until my brass gets fully expanded , 2 or 3 cycles . then I full length size by adjusting my die to bump the shoulder about .002" . if you neck size only , you will reach a point where the brass gets very tight to chamber . BR shooters have got away from neck sizing only , they size brass with the .002" shoulder bump .
I have just gotten my feet wet with my .280 Rem brass from them, and so far am greatly impressed. Brass appears to be of high quality. Weighed a sample, and consistency is better than my Nosler/Norma. Annealing "feels" spot on in sizing.
Fired the best groups ever in this rifle with it. We'll see how it holds up over repeated firings, but so far it's a winner.