According to some info I have read, there are powders available for large doubles where a Filler is not needed..I believe 500 Nitro had eluded to those in previous posts-- the reason I have gone with RL-15 is two fold---one --the gunsmith I sent my double to (Ken Owen) for some work suggested it--and once he put together a load it shoots very, very well in my double..

Secondly, several articles I had read as well as visiting with others on this site stated they had good results as well...

Peronally, I think the issue of fillers has once again been blown way out of proportion because of the guy on AR using the wrong powder with his ...I am enjoying great results with mine and don't plan to change a thing...

Ripp