The phrase "sheer amount" refers to a very large quantity or number of something. It emphasizes the overwhelming and considerable size or volume of a particular thing. Full definition
As far as the number of weapons and perks available are concerned, I feel their current offering is fantastic, as it allows for everybody to choose a weapon of their liking, but the advantage held over other players will never be insurmountable because each weapon has an advantage as well as a drawback, allowing for skill to take precedence over sheer amount of time played and the weapons awarded because of it. (jamiex66.com)