I have a batch of loads that I've compiled from various places on the Internet... mostly match bullets in the 120 or 140gr class and longer barrels (26-30"). I can email them to you in the morning if you want.
The gist of it is that if you are interested in the heavier bullets i.e. 130-140gr you probably want to stick w/ the slower powders... H4350 works well, as does RE-19, H4831, N160. So far I've had pretty good luck w/ RE-19, 47.5gr behind a 123gr Lapua Scenar, others have had good luck w/ 43 grains or so behind a 142gr SMK. I've had excellent results from about 42-43gr of H4350 behind a 142gr SMK as well. As a general rule, most people seem to stick w/ the mid-to-slower powders rather than Varget, 4064, RE-15, with the exception (isn't there always one
)of a number of serious competitors use 38.0gr Varget behind a 142gr SMK. A few guys go the opposite way and try the slower powders such as H1000 or RE-22 in order to try to fill up some of the air space in the case (most normal loads in a .260 only fill to about 75-85% or so). One guy is pretty successful w/ a *large* amount of H1000 behind a 142gr SMK; but he has to use a Winchester case and a drop tube to get it all in there
The 6.5-08 is just a smidge behind the 6.5x55 Swede which is just a smidge behind the 6.5-284. There is enough difference though that I wouldn't try using the load data from a 6.5x55 as anything other than a(very) rough ballpark idea for how much powder to use in a .260 Remington.
If you were just fireforming... unless it was a serious full-bore balls-out load, I wouldn't worry about it too much if there is a tad of unburnt powder in the pipe after the shot. If it shoots well, go w/ it.
HTH,
Monte