and would also like to know how it would fare at 900/1000 yds,
(Re 175gn SMK at .308 Win MVs)
Not very well is the answer - only marginally supersonic at 1,000 from a 25.5" barrel rifle and you risk having a mix of super and subsonic bullets at the target. This is an 800yd bullet and its BC is mediocre compared to many recent introductions. It's a very good performer at 200-600yd, although its low BC will have an effect at the top end of that range in difficult wind conditions.
G7 BCs (source: Applied Ballistics for Long Range Shooting 2nd edition)
Berger 168 VLD .......... 0.242
Berger 168 Hybrid ....... 0.266
Berger 175 BTLR ......... 0.264
Berger 185 BTLR ......... 0.282
Berger 185 Hybrid ....... 0.291
Sierra 168 MK ............. 0.218 (not suitable for 1,000, usually becomes unstable)
Sierra 175 MK ............. 0.243
Sierra 180 MK ............. 0.247 (not suitable for 1,000, usually becomes unstable)
Sierra 190 MK ............. 0.268 (very stable at extreme ranges including going subsonic)
Lapua 167 Scenar ....... 0.216
Hornady 168 A-Max ..... 0.230
The Hybrids are in the process of being introduced and not yet available here. In the meantime, the best bullet going for an AI at extreme ranges is the Berger 185gn BTLR - if you can (a) find them in stock and (b) afford them - not a cheap bullet. Its lighter 175gn Sibling is very popular amongst US sling shooters in matches that allow any bullet weight to be used.
Also don't forget the better 155s - the new Sierra MK #2156, Lapua Scenar and Berger 155.5gn. Any of these will perform better at 1,000 than the 175 SMK if pushed to a decent MV. (You need a minimum of 2,800, much better still 2,850 fps.) The new Australian HBC from Fox Firearms has performed very well for me, is a ballistic match to the American / Finnish trio and sells for £280 / 1,000.
The 190gn Sierra MK is a tried and tested long-range performer and is cheaper than the heavy Bergers.
Both 185 Berger and 190 SMK perform well over Viht N550.