I would go with the 650mm 6.03 barrel, you use HPA so you should see a velocity increase with the longer barrel. By the way, nice rifle!
However, the bad thing about a barrel that's too long is that it tends to wobble, so put a ton of spacers on it!Thanks for comment![]()
If I had the option to go for that one, then I probably would too.I would say go with a 6.03 510mm, unless you are using the extra length to try and out an LRB in it.