Maybe the load data takes into account much deeper seating of the bullet than your loads? Does the bullet you're using have two crimp grooves? I'm just speculatin... 
Trailboss powder loading formula
I was on another forum and there is a bit of a disagreement on the loading of Trailboss powder. IMR load data shows a max load for 45 colt of 5.8gr at about 12,700psi with a 250/255gr bullet. Also on IMR website (same site as load data) there is a couple paragraphs describing how to come up with "your" reduced load using said powder. This is accomplished by determining the space your bullet occupies in the case and filling the case with powder to that point. (NO COMPRESSING) weigh this amount and this becomes your MAXIMUM load. Use 70% of this amount for a start load and work up toward your max load looking for the most accurate loading for your gun. My measurements are: 45 colt starline brass, 255gr Lee RNFP, I can get 8.5gr of trailboss up to bottom of bullet with no compression, this would be my MAX load, 70% of this is 5.9gr as a start load. As you can see this is over the max load info of 5.8gr. in the load data. WTF over.. anybody got an answer for this one?? Don't say call Hodgden, tried that, they ain't talkin..Another question, if the 5.8gr. load has approx the same pressure as say, 8gr. of Unique why is the recoil so much less? Seems like every time I increase pressure in a load the recoil factor goes up...I may be sly like fox, but I'm also smart like tractor..
anybody got an answer for this one?? Don't say call Hodgden, tried that, they ain't talkin..Another question, if the 5.8gr. load has approx the same pressure as say, 8gr. of Unique why is the recoil so much less? Seems like every time I increase pressure in a load the recoil factor goes up...I may be sly like fox, but I'm also smart like tractor..
