There are many on this board that have more experience than I do, but for my two bits worth you need to jump that Leupold up to 14 or 20 power. I have 3 Leupold VX IIIs and for 1000 yds I want to be using the 6.5 x 20 LR.
I use a lot of Leupold Scopes and I would suggest you use a higher magnifacation such as the 4.5-14x50 or the 6.5-20x50 both in Mark 4. The addition of a good reticle should be considered also. Holland reticle is an excellent choice and that is what I run on my Mark 4's. I have the 3.5-10x40 you are questioning on a DPMS SASS rifle and it is Great out to about 700 yards for precision work. You have a great field of view also for close range on the lower power setting. That is one of the draw backs on the 6.5-20 and the 8.5-25 Mark 4's is the field of view on low power is limited. The 4.5-14 maybe your best choice for the all around scope for close and long range if you are set on going with Leupold.
Thanks for that very helpfull .
I considered the 4.5-14 but i just dont like 50mm bells. Dose NF make a scope in that magnification with a 40mm objective.?
And how do the NF scopes compare in price to the mark 4's .
Just looked at NF Catalog and didnt see a 40 mm Objective. I have a 3.5-15x50 NF, 5.5-22x56 NF and had a 8-32x56. Good quality scopes. A little more cost than a leupold and I believe the optics of the NF are better out past 1000 yards. If you really shop around the net you can find some pretty good deals on any of these scopes. IF you go with a NF try and get the NP-R1 reticle. It is a MOA reticle and will match your MOA turrets on the scope. The NF turret has 10 MOA per 1 complete rotation and the Mark 4 will give you 15 MOA per 1 Complete rotation. NF power ring when turned also moves the entire eyepiece so if your gonna use BC Caps you will need to position them in a manner to where you can still turn the power ring and not interfere with bolt operation on your weapon.
You can buy the scope directly from Holland with reticle already installed or send your Mark 4 to him and have it installed. I personnaly sent mine to him and had him install the reticle as I already owned the scopes.