Assuming factory loaded ammo, what's the best bullet weight .308 Win for ling range (500 and up) yards?  

Is 168gr good and the Federal Gold Match a good ammo?


Still far from starting reloading so I would like to start with a good quality factory ammo and then move up to hand-load, reload.

175 is better, FGM2, BHM, HDY, etc.

175 FGMM or better yet ABM 185

Generally speaking (for pointed bullets), the heavier it is, the higher the ballistic coefficient. High BC bullets will give you the advantage in wind, and do a better job of holding onto their speed. While a heavier, slower bullet will have more drop at intermediate distances, they will maintain that speed until they are moving faster than the light bullets at long range.

For your specific rifle, you must also consider what your barrel will stabilize. If your twist rate isn't fast enough, the bullet will start to tumble as soon as it gets out into the open air. If you normally shoot in hot and high environments, you may be surprised that a bullet that was flying well for you becomes unstable on a cold day at a range close to sea level.

My suggestion is that once you find something that works reliably, then buy a large enough quantity of it that you can do all your practice without having to collect data a second time. A chase after peak performance will lead you to something other than .308, don't let that distract you from learning to maximize what you have.

Thanks!   I'll get a couple cases with different weights to compare.

FGMM is decent enough that HS Precision uses it for their accuracy testing.  

However, whether it'll work for you depends on how far you're talking when you say "up" in "500 yards and up".  The 168 gr SMK doesn't transition well to subsonic velocity, so it's limited to ranges where it'll stay supersonic.  The generally means the 168 gr SMK is capable but only out to ranges of about 800-900 yards in the .308.
 
The M852 Match load used the 168 gr SMK but at only 2550 fps and on a standard day it would go sub sonic around 850 yards.  

The old M118 Special ball used a 173 gr FMJBT at 2640 fps and it would go sub sonic at around 990 yards, and it transitioned much better, without the loss in accuracy that M852 displayed when it went sub sonic. The bad news was that the 173 gr projectile started out being accurate enough  at around 1.25 MOA to 1.5 MOA, but as the tooling wore the bullet weight started to vary a lot and accuracy fell to the 2.0 MOA range, to as bad as 3.0 MOA in some lots.  

Snipers back in the day would use a 500 yard basic zero and then engage targets from about 500 yards to about 800-850 yard which was considered to be about the maximum effective range for the .308.

However, if you load the 168 gr SMK to a similar velocity, you get similar performance.  I load them to 2665 fps in my 20" Model 700 and they'll go sub sonic around 990 yards as well.  It's not quite a 1000 yard load, but it works for 95% of the shooting I do. The Federal GMM load has published velocity of 2650 fps and will give the same performance, assuming you get that velocity on your rifle.

What twist?  Conventional wisdom seems to suggest that the heaviest bullet you can reasonably stabilize will have the best BC and will usually produce better performance especially at extended ranges.  Having said that, for a 1:12 twist, I am partial to 168 grain bullets.

Agreed. I have been shooting a 26" VSSF that will shoot sub moa with almost everything, but it shoots a hair better with 168s. I attribute that to the 1-12" twist. I could be wrong though. 

This.

Hornady's 178 grain projectiles work great in both my Remington and Savage.