With the above in mind would I be better switching to RS60? Is RS60 the same as RS62 in that it’s between single and double base?? (I believe it’s like an I between in the case of RS62)
Reload Swiss powders come in two forms. There is conventional single-based tubular (eg RS50 and 62). Then there are 'high-energy' grades, all of which also have the unique 'EI' enhancement. 'High-energy' powders take a standard single-base type and late in the production process infuse the granules with nitroglycerin. If you're an energetics chemist this is technically different to 'double-based' which as the term suggests sees plain nitrocellulose and nitroglycerin mixed together in paste forms early on to provide a double-base material that is then rolled, extruded or whatever. From the user's point of view, there is no difference between 'high-energy' and 'double-based' - they both contain nitroglycerin. A high-energy type with say 15% nitroglycerin content by weight will outperform a double-based type with 5%, but also increase barrel wear.
'High-energy' powders aren't new in the UK. All Viht N500s are of this genre. In fact Nitrochemie Wimmins A.G., the RS manufacturer, developed the process and sold it to Vihtavuori Oy many years ago.
What is new with all Nitrochemie high-energy grades, and is unique to them, is the 'EI' infused deterrents technology. Deterrents are the chemicals used to change initial burn, normally slowing it, to keep pressures in check. Traditionally, they are surface coated, and whilst they work very well, it's a one-off and very short-lasting effect. 'EI' powders have infused deterrents inside the granules and their effect is longer lasting. This means that if you look at the pressure - time / bullet movement graph, the initial peak pressure shortly after ignition and as the bullet just gets underway is extended - ie lasts longer and for a greater length of bullet travel.
As it is total and not peak pressure that governs MV, ie the area under the pressure-time curve, this gives higher MVs, within any pressure ceiling. That's the RS 'EI' upside. However, it also extends the area of throat / leade / rifled barrel that is exposed to peak pressure and temperature gas, and also extends the time-duration of those destructive conditions. It's the pressure/temperature extent and time duration that wears barrels out - literally washes the steel away at the molecular level and changes the metal grain structure.
The 'EI' bit is the revolutionary change in these powders. RS60 / Alliant Re17 provides startling MV increases in some catridges, eg 6XC and 284 Win with + 150-200 fps MV with heavy bullets, and most of that comes from 'EI', not high-energy. (Compare Viht N140 with 540, N160 with 560 etc MV changes - they're nothing like as great.)
How much additional barrel wear do they incur? That's very difficult to answer as it depends on loadings/pressure-attained and rifle usage. In the worst scenario - US F-Class and Benchrest competition and prairie varmint shooting employing absolute maximum loads and shooting in high ambient temperatures using 'string shooting', barrel heating was extreme with barrel life cut in half or by even more compared to 'hot' loads of Hodgdon equivalents like H4350 and H4831sc. In UK F-Class where we shoot with heavy jackets on in mid summer sometimes and we pair-shoot (ie two competitors alternatively on one target), many people have used RS60 in 284 Win for example with perfectively reasonable barrel lives. Crucially though, they do not load fully up to what the powder allows and take a modest performance enhancement. Increase 284 Win MVs with 180gn bullets from the usual 2,830 fps or thereabouts to the next node in the mid to high 2,800s and you're OK; push MVs way up in the 2,900s towards 3,000 (which RS60 will allow) and the barrel is soon toast. So, if full performance enhancements aren't taken and the number of rounds fired is both low and at a slow rate of fire as in most UK field shooting, additional barrel wear will either be marginal, or at any rate not so extreme as to be an issue. I wore a stainless match barrel in 6XC out in just under 1,000 rounds - acceptable for BR which it was used for, less so for F-Class which involves higher round counts. Crucially, Re17 (this was pre-RS days) took me to an MV level that was essential ballistically / competitively and which Viht N550 couldn't achieve without producing excessive pressure. 6XC is supposed to have a 2,000 round stainless barrel life, but for this type of competition will be much less, so realistically barrel life was reduced by somewhere between a quarter and half. But that's guesstimate!
With the uber-heavy bullets now being made and increasingly used and propellant improvements, people do have to consider barrel life much more, especially with rebarreling with (softer) stainless steel products far more common nowadays. People really need to think carefully about regular range days with quite rapid fire (especially with electronic targets coming into use) and high round counts. Many of today's common or garden cartridges have much higher capacity to bore area ratios than 223/308 and we're not shooting surplus 7.62 Nato with 145gn bullets at 57,000 psi pressures at large targets anymore through very hard hammer-forged chrome-moly barrels. With 2-3,000 round barrel lives and the best part of £1,000 to rebarrel, the barrel cost per shot is no longer insignificant. Great fun to put 100 rounds down Stickledown in a day in non-competitive shooting, but round-counts soon mount and the barrel stops performing long before you expect! Also, C-M barrels + 7.62 + light bullets eventually saw heavy but gradually incurred throat / leade wear. The low rate of wear + hard metal kept worn barrel surfaces smooth. Pressures / MVs dropped, but barrels continued to group adequately well past their replacement points. Stainless + high temperatures / rapid wear produces anything but smooth surfaces ahead of the chamber. As a result, today's much higher intensity cartridges and propellants, heavier bullets +stainless sees performance drop off a cliff over a few rounds, sometimes between two consecutive rounds if a chunk of rifling land breaks off and leaves a 'pot-hole'.
