Mac, in my first season of GB national FTR shooting, I used a 12-inch twist 24-inch barrel FN SPR and the 175gn SMK over IMR-4064 in Lapua brass. This was early days, no Berger Juggernaut or long-nose tangent ogive bullets. The MVs ended up not much above the M118LR, as the rifle didn't like really hot loads. Back then in the 'oughties' and year 1 of FTR people were writing that the FN SPR and similar were FTR-capable out of the box rifles. Generally, they weren't in truth, or not at least for 900 and 1,000 yards fixtures.
At 1,000, I hit the target often enough, only rarely in the middle though. A long, long time ago, the US Army did extensive tests on the old 173gn FA FMJBT bullet at longer ranges at .30-06 velocities. Their conclusion was that keeping it supersonic was near vital, but also that supersonic plus around 100 fps was also vital at the target, ie ~1,230 fps because of transonic instability and turbulence / increased drag. Drop below that value and group dispersion and wind drift both increased dramatically. That's exactly what I found with the 175gn SMK at some 2,650 fps MV in 900 and 1,000 yards matches. Wind changes that were a half minute for others with ballistically competent kit were doubled, elevations went to pieces etc, etc. In cold days with headwinds, it was obvious that some bullets were dropping below the speed of sound at 1,000 and I was in the trap of some just super and some subsonic, which let me tell you, provides appalling results on the paper. All this was when we used G1 BCs and Sierra tables and suchlike which said the bullet should be doing ~1,225 fps at 1K, so these occurrences were extremely puzzling. Now we have G7s and Bryan Litz's experimentally obtained values and know somewhat better as to what is really happening.
Until I could get a proper FTR rifle and shoot the then new 185 Juggernaut at 2,800 fps plus which I did with some success in FTR year 2, a stop-gap was found with the 190gn SMK and some really stiff Viht N550 loads that produced around 2,575 fps IIRC. I had spoken to the GB 'Match Rifle' shooters who shoot the 308 at up to 1,500 yards and who had found through trial and error over the years that the old 190 and 200gn SMKs were extremely tolerant of transonic speeds and getting into subsonic flight beyond the 950 yard or so mark. (MR shooters now use heavy VLDs and Hybrids like FTR shooters, the old 190/200 way surpassed by more modern designs.)
Yes, I know that hotter climates and high altitude ranges can tip the 175gn SMK back into the supersonic band. It doesn't at Diggle or Blair Atholl in the UK though despite their 1,000ft ASL elevations, but not helped by their having few warm and no hot days in an average year. (It's all relative of course. I shot against the US FTR team at Blair in June 2011 in what was a heatwave for the Scottish Highlands and most of us Brits were uncomfortably hot. I asked Michelle Gallagher how she was finding the weather and her reply was that she felt downright cold not having acclimatised to the Arizona to British Isles switch despite this being about Day 12 for her having shot against the RoI at Tullamore in Ireland in the inaugural revived Creedmoor LR Matches the previous week.)
Don't get me wrong. The 175gn SMK is a fine bullet, and very good value for money. It is very easy to tune in most 308 Win barrels and chambers. It works a treat at 600 yards and suffices at 800, although even at those two distances a higher BC bullet is going to walk all over it these days in FTR competition unless the winds are being very steady. It can give superb precision. My FN SPR 175/4064 combination produced a 0.1" 5-shot group at 100, one of the very few groups I've achieved in the low ones with non-BR rifles over many years and in the days when we still shot UKBRA 300 yard winter season BR matches, it was competitive in the 'Factory Rifle' class. BUT ... it is not a great FTR bullet these days simply because it has been overtaken by so many much more efficient designs with lower 'form factors' and higher BCs, many of which will work very well in a 12-twist barrel. The 175gn Berger Target LR BT is a good example, likewise the Berger 175gn OTM Tactical, and the 185gn Juggernaut which whilst not optimised in a 12-inch twist will still work well enough to win matches. They do everything the old SMK does and a lot more, the only downside being you pay more for the best.
