Do any of you have any experience with 50 bmg uppers for ar lowers? Watsons seems to be the cheapest but I don't like the way it loads. I've found some threads on here about 50 uppers but there are 2 or 3 years old. Any new info? There were some links for ultramag 50s, mmag (link didn't work) ferret, etc? Does any one make a true bolt action upper for less than $1500?