In many ways, this is one of the most impressive OFP missions ever made. This is modeled as close as possible to a real life Sniper Firing Training Exercise in the US military. Unless you're already a professional spec-ops trained sniper, you'll probably fail this mission more than once because you did not read or follow exact orders.
You can play the Sniper Range mission with any version of OFP. Sniper Range takes place on Malden Island. No unofficial addons are used. There's no wasting time around here with introductory cutscenes or music.
Start off by reading your mission plan, studying the boundaries and terrain of the exercise area's map and then memorizing the must-read notes. Every detail should be taken seriously. One breach of orders or misconduct during this exercise and you'll be assigned to mission-retry hell, soldier!
You start off at the southern outskirts of good ol' Dourdan. It's just you and your M21. You've got a long and treacherous way to go till you evade all patrols and finally spot your primary target. Don't get trigger happy. Remember, read those instruction notes carefully so you do the right thing before you take the kill.
When you're ready to head for the extraction point, far far away, you'll need to be just as stealthy as you were on the way up.
And remember: this is an exercise. Good luck!