The OP's question shifts from Re17 to Re15 mid post without skipping a beat - typo or intention?
My experience with the 6.5X47L and backed up by many other users I've spoken to is that there are most unusually two groups of rifles / barrels 'out there' when it comes to 120-130gn bullets. Some perform brilliantly with H. VarGet, Alliant Re15 and one presumes with other powders in this general burning rate such as Viht N540 and the new IMR Enduron powder (we've yet to see any in the UK). Others, my own rifle included, will not produce anything like decent groups with this powder class, but move onto something a bit slower burning such Viht N150, N550 and the 4350s and results are transformed.
So, the first thing is find out which of these groups your barrel likes and as a rule ignore well meaning but sometimes misleading advice on the lines of such and such a powder is THE ONE to use.
If you have a VarGet lover and you can actually get the stuff (an even bigger issue in Europe than the US believe it or not - the European importer now has a staggering 15,000lb on back-order!) then that is still usually the best choice, although a minority on this side of the Atlantic anyway prefer Re15. My experience of Nitrochemie Ei-N130 (RS52) which goes back to trial bulk batches imported here a couple of years back is that wherever VarGet works well so does this powder, and usually at very similar charge weights. (But RS52 is usually capable of producing higher MVs, no doubt at the expense of shorter barrel life, it being a 'high-energy' propellant with infused nitroglycerin.) In my 6.5X47L it produced excellent velocities and very similar groups to VarGet and Re15 (ie very poor!).
Alliant Re17 / NC RS60 has a similar burning rate to N550 and the 4350s, so should be an acceptable, maybe excellent, performer in the cartridge if you have a 'slower powder lover'. Two things are certain - it'll produce higher MVs than the 4350s can do safely, and if you load for and use that extra 75-150 fps, you'll see a considerable increase in barrel wear and tear. My own entirely personal view is that it's also not quite ideally suited to the case capacity / charge to bore ratio and that makes it 'finicky' - it'll sometimes work brilliantly, sometimes not, and sometimes both things in a single cartridge / rifle. (I've seen this afflict several people and not just in this cartridge.) Go down a calibre with the same case size and it's a different matter - the 6X47L, 6XC, 6mm SM and SMACK (Swiss Match and SM Ackley), 105s and Re17 usually takes some beating - small groups, fantastic MVs, small MV spreads, cr*p barrel life.
I'd say that if your rifle prefers the slightly slower burners, H4350 will most likely turn out to be the best choice on the round and covering all conditions. Since we can't get it here either, or at any rate only occasionally and often at considerable expense, Viht N150 is a viable (and MUCH cheaper) alternative for us in Europe, although it's a bit 'pressure-spiky'. I've also been playing with another Nitrochemie RS powder that is Europe only so far, RS62 which is very similar to traditional long-cut 4350s. Originally developed by NC for the .270 Winchester as a basic no-nonsense single-base tubular propellant, it looks like it may also suit the 6.5X47L with 120s and upwards, having had good results with the two new Lapua Scenar Ls (120 + 136gn) in testing. The 136gn version will get its first competition outing next weekend in a 500 yard 'Fly Shoot' comp, so I'll get an idea how it'll likely do in mid-range F and BR. Like older IMR powders, it is a sod to measure in the RCBS Chargemaster though, regularly over-throwing charges by 0.2/0.3gn - I'll have to look at drinking straw mods.
The other factor to bear in mind with Re17 / RS60 and other high-energy types such as N550 is one we rarely worry about much in the chilly UK (and it is just that here today, barely in the 60s!) - temperature sensitivity. Re17 has acquired a reputation for that if the various posts on this forum are to be believed. Even here in Britain, some explain its 'finicky' / inconsistent performance on this factor, the powder maybe having a narrow pressure band where it really performs and a temperature change taking it out of that - sheer conjecture, but maybe just something in it. That would also apply to RS52, but not RS62.
