I am having a custom rifle put together. Looking for a long range rifle, caliber 338/378 Weatherbe or 30/378. I know it will be on a Remington Action and a 30 or 32 inch barrel. This is my first custom gun being built, how would you reccomend putting it together; what barrel, what twist, etc. The guy seems nice and knows his stuff, just wanna make sure I'm not going to be ripped-off.