I will admit I'm no genius, but here are some tips that I find useful when engaging in long range combat.
First off, we will start with the Recon Kit and different loadouts.
Your primary weapon should reflect the map you are palying on, on maps that are smaller (i.e. Grand Bazaar) the semi-automatic rifles should be your choice. Wheras on longer range maps (i.e. Operation Firestorm) a bolt action rifle should be used.
Next, the specifc rifle.
From what I have seen, the two best general useage bolt action rifles are the L96A1 and the M40A5. The L96 is better for lower profile engagements (as it can accept the flash suppressor) and the M40 is good since it has the fastest bolt cycle. At long range, the M98B is the superior weapon.
As to semi-automatics, I wouldn't dream of touching the SKS. It is not a sniper rifle. The two best (in my opinion) are the M39 EBR and the QB-something in the BTK expansion. Each has benefits and downs in comparison. The M39 has a better scope and the QB has less bullet drop (I hate the Russian scope, it has less zoom and uses stupid chevrons).
With bolt actions there are different variations that suit different roles. For long range shooting, a ballistic scope and a bipod (with a flash suppressor for the L96) are the best choice. For a medium range or more on-the-move role, using either the default scope or the ballistic with a straight pull bolt should be the attachments. For a close range lower profile role, using an ACOG scope with the straight pull and a suppressor is the best choice.
At long range, having steady aim is better than having better fire rate. Therefore the bipod is the best choice.
For an on-the-move role, fire rate does beat lack of sway and a good scope is essential.
For close range, the suppressor will keep you hidden as will the ACOG (as it has no scope glint).
Never use the suppressor at long range, the only reason to use it is to remain off the radar. So if you're 200 something meters away, you won't show up on an enemies radar.
If you're using a bipod since you don't have the straight pull at medium ranges, never just sit there with the bipod deployed aiming down your scope. I cannot say how many enemy snipers I have killed because they did this. 7x, 8x, and 12x scopes cause glint when aiming down and this can spell your demise.
Laser pointers are not a very good choice, I cannot say how many times enemies have saved my life by aiming a laser in my eyes and showing me where they were. As a Recon, you want to stay off the radar. You want to have the lowest profile possible (within reason).
When it comes to Semi-automatics, in general using either the standard or the ACOG scope should be the biggest decision, I'm no semi-auto specialist.
This is a major choice when it comes to the Recon kit in particular. Your sidearm should be one of two extremes and must work as a stand alone weapon. Either one of the selective fire handguns (M93R or G18) or one of the revolvers (preferrably the MP-412 REX). Your sniper rifle is worth almost nothing at close range therefore you will need extra ability to make up for this.
These will mimic your rifle. The TUGS is good for close range when you need to see where the badguys are. Employ it at close range. The SOFLAM is good both at long range and at medium range. I really don't like the MAV but it can be useful as a mobile TUGS or as a vehicle to piss off enemies by ramming them.
Notes on the SOFLAM: Never ever, ever, ever be very near your SOFLAM. Enemies will see it and if you are near it they will see you too. The Javelin can lock onto the SOFLAM and you do not want to be near it when the Javelin hits.
SPRNT is the best choice, next best could be either SUPR or COVR. SPRNT will allow you to get to where you need to go faster. The other two will allow you to either take less covering fire from enemies or to put more on them yourself.
I hope that this helps and brings you victory. Whether you be in my crosshairs or by my side in combat, good luck! (Though not so much if you're in my crosshairs :D)