For "long range", the 168 is not going to provide consistent or reliable results from a .308. Moderate ranges, yes, but true long range, no.
In addition to shooting quite a few of those rascals myself, I've shot with and against them. I've also helped teach long range precision rifle classes at Quantico, which were attended by LE from several states, military and civilian shooters.
Invariably, we will get a student who, while never having actually shot to 1,000 yards with their duty rifle, feels quite strongly that their 168 SMKs (FGMM or BH) are going to be "just fine". Even though the class prep docs specifically warned against trying to use 168 SMKs for this class, there was always that 5% . . .
Invariably, we will have that person begging or buying 175 grain ammo from someone so they can finish the course.
The 168 SMKs really are superb at closer ranges, which can be misleading.
They get so far back and their bullets no longer hit where expected, and the pit crew advises that "someone" is getting sideways hits and that their bullets are sub-sonic. It is easy for the pit crew to recognize sub-sonic projectiles, because they are lacking the characteristic sonic "crack" at accompanies a happy bullet.
At near sea level (typical density altitudes from -1,500' to +1,000) areas such as Quantico, the 168 SMK is almost guaranteed to turn sideways by the 800 yard line. This is especially true of short barreled "police tactical" models, and longer barrels will sometimes do OK to 900, but at 1,000, it is nearly impossible to drive a 168 fast enough from a .308 to keep it from going trans-sonic and destabilizing at that distance.
In the mountains, at 3,900' ASL (typical density altitudes from +3,500' to +7,500) where we shoot the Allegheny Sniper Challenge, the 168 will perform much better, and may not go trans-sonic before 1,100 yards. Even so, it still lacks any performance benefit that would suggest their use. Any close range accuracy advantage is quickly lost, due to it's sensitivity to wind and pronounced drop at extended ranges, even *IF* it does manage to stay nose-on.
While the 175 SMK begins a little slower, and may deliver a 3/4 MOA 100 yard group in lieu of a 3/8 MOA 100 yard group, it enjoys a MUCH better ballistic coefficient and far greater stability. It is not only more resistant to wind drift at all ranges, but by the time we get to 600-700 yards, it surpasses that 168 SMK in all aspects; drop, drift and retained velocity.
While it is relatively easy to compensate additional drop, and no one *really* cares about their exact terminal velocity, drift just flat out kills you, because the wind over that much real estate become VERY difficult to dope with real precision. What may seem to be a tiny fraction of wind change, 1-2 MPH, nearly imperceptible at the firing line, especially when we talk about the difference between an 8 MPH breeze and a 10 MPH breeze, becomes a difference of a center hit and complete miss surprisingly quickly.
Bottom line: Trying to use a 168 SMK from a .308 at *true* long range is a well-documented strategic error and to be avoided.
