I'm building an M4 stlye carbine, but I've always loved long range plinking, so I'd like to put a variable leupold scope on an A3 upper for this purpose. My question is this, what kind of accurate range can I expect from a 16" barrel vs a 20", and is it worth the extra money for a stainless barrel for added range? I realize that carbines usually aren't inetended for extreme long ranges, but I'd like to see just how accurate I can get it to be.
by the way, does anyone have any advice on scopes? I'd rather not spend more on optics than on the rifle itself, but I like the idea of a variable scope allowing the shooter to click between medium and longer range lenses.
There is no accuracy difference between the 16" and 20"...the shorter barrel will produce slightly less muzzle velocity, meaning less effective range, but more than enough for what you probably have in mind..300 yards, in that vacinity?
Chrome lined bores are more durable and easier to clean, but slightly less accurate than a non chrome lined bore. You don't need a bull barrel to get an accurate rifle, a lot of match style rifles just use the standard HBAR config. A stainless barrel won't give you any more range than a plain steel one.
If you're on a budget, I can recommend either the Weaver Grand Slam 6x20x40 for around $340, or a Nikon Buckmaster 4.5x14x40. I have one of each, and they're both very nice pieces of glass. I got the Grand Slam at SWFA's suggesion instead of a Leupy, so you don't just have to take my word for it. The weaver is perfect for any kind of target/varmint work. The Nikon is a great little scope, and goes about $60 less than the Weaver.
Variable scope don't click between different lenses, they have a knob which rotates between differing powers of magnification.
Stick w/ the Leupold as a scope choice then atleast when you find out you have NOT gotten the barrel for accurate extended range work, you'll only have to replace the barrel, not the scope too.
As to the range of 16" M4s, my 1/7 chrome-lined using 77 SMKs has an effective range of about 400 yards max when aimed at "chest" sized targets, past that hits are more a matter of luck. Of course this M4 is equipped properly with an Aimpoint ML2 on an ARMs #45, not a precision optic Leupold which resides on my 24" CR6724 where it does the most good.
The CR6724 will drop 77SMKs in chest sized targets at 1000 yards in good air when the shooter does his part, btw.
IMO, a quality (Krieger/Pac Nor/etc) 16" stainless steel bull barrel will actually stand the best chance of coming close to your desire, despite what is mentioned above, but the "velocity-loss" portion is dead on and will hurt and limit your effective range.