Re: barrel length and contours
Your question is asked by many of those wondering about caliber and barrel diameters.
First, I don't know what you mean by the "Plus" after 600 yards. Lets use 600 yards to 1000 yards for Texas deer.
To give a quick response to you and making it as easy and inexpensive to start out as possible. You can't go wrong with a factory Remington 40X with the 27" barrel and the 300 Winchester mag. caliber.The stainless Sendaro in the same caliber will work just fine also. For larger elk and mule deer I would go with a 300 Ultra or even the 300 Weatherby or an Improved Weatherby and a custom barrel and longer length.
The barrel diameter of the 40X is .850" and works out very nice.
There are a host of longrange guns being built by Savage and one would be very pleased with them. I have one with a custom Hart 30" barrel on it and it is a fine rifle.
The factory contours in the Varmint styles are very adaptable to light weight carry guns that can be used for a medium (to 1000 yards) longrange outfit.
Just as important as the rifle is, the scope. It needs to be top quality with target knobs preferably 1/4 Min clicks.
Practice is the key.
Know your rifle and scope and what the clicks do at all the ranges you intend to shoot.
A good rangefinder will be needed along with a good set of bigeyes. After you have all that, look for a hunting partner to help spot the shots and for you to do the same for him.
The above information would get you into the LR game as inexpensive as possible by use of the factory configurations.
30 Cals are used the most for the duel target and hunting situation in the light weight guns.
Hope this helped you a bit.