Yes, however keep in mind you are viewing the infrared energy from heat, and it's the differences in temperature that provide your image. This means the closer your target is to it's surroundings, the less obvious it will appear.
yes I have mine sighted for multiple ar15s, in multiple calibers and loads and an ar10 and it is extremely close to if not dead on each time I re mount it. it saves multiple sight ins so I have one for 300 black out subs and one for supers, one for 308 win, and 1 for 223. just make sure it goes back in the exact spot it was at before Ie if you have t marks ona flat top upper.
I have mine on my 30-378 weatherby magnum and it handles everything I’ve thrown at it. So absolutely will handle your 300 win mag.
According to AGM's site, the V2 scopes have a 50hz refresh rate over the V1's 25hz