I would be more concerned with weight distribution and balance that barrel length. As is evidenced here, you can load any length of barrel easily. So the length of trigger pull comes into play as well as where the weight IS in the rifle. For example, if your barrel is 1" across the flats without taper or swamp, and 42 - 48" long, you'll have to be very strong to shoot it offhand, even once. But if the barrel is nicely swamped and the LOP is correct, a very long rifle can be handled nicely. My observation is that most shooters and builders think one needs a minimum of 14" lop. I'm 6'2" x 240 pounds and prefer 13 1/2" of lop with a drop at the comb of around 1 1/2". That gives me a rifle that I can shoot all day long offhand.
