12 inch drop tub and tapping let me load 25.5 gr at mag length, with crunching of course.
That was the load that I blew primers on. Before that, I had shot a decent number (between 50-150) of that load with mild cratering on CCI 450s and flattening on Fed 205s. 2778 fps from a 16.5 inch barrel suppressed using FC brass.
25.0 gr looked similar in testing but I did not load nearly as many.
Currently I'm using 24.6 gr for 2700 fps using fed 205s in Federal 5.56 brass.
According to my notes I got 26.0 gr of N140 in Sig brass and no pressure signs, I found both N135 and N150 to be more accurate than N140, so other than burning up the poundbin target loads, I did not play with it much. But, given that the Sig brass has a smaller water capacity than FC and that N150 is a slower powder, I was falsely confident in 25.5 gr being fine.