Bruce -
My experience with the 260 and 140 (no 142's tried yet) grain bullets indicates best velocity/accuracy with two powders, primarily - H4831SC and IMR7828.

R-WEST

I've found really nice loads with 129 Hornady, and 125 Partitions with R19. I have not had time to mess with other bullets yet. Both bullets are around 2900 fps and sub moa. I am really happy with the 260.

I have been using the 140 gr core-loc bullets in my 260 ruger using Imr 4831 and 44 grs.what load are you using in the R-19 and 129 gr bullets? I want to try the new 129gr SST from hornady next.

I find R19 seems to give the best velocity in my 260 with 140 gr Hornadys but H4831 is VERY close and gives better SDs in my loads. For the 120s and 129 Hornady I use H4831 with best results comeing from the 120s.

Reloader 19 works well for me with 129 grain Hornady bullets and 140 grain partitions.

Alliant's web site show a max load of 46.0 with r19. I have a custom cut chamber which doesn't really let me get there without really spiking the pressure. The 129 sst is my next stop for testing. The only place I've seen them advertized is in cabella's. Has anyone found a better source yet.