I know what powder bridging is, as explained to me by Kirby. I did ask about the smaller cuts of extruded powders to be used in the 270 AM, as I own one as well. My question is this, is bridging a substantial issue when the case is not completely full, and it is horizontal in the chamber, ready to fire? The powder will rest in the case with gravity, filling the bottom shoulder but not the top.
I was wanting to try the 7828SSC and Reloder 25. The reloder powders are of the extruded type, but are small cuts anyway. And, I've yet to use a magnum rifle of any caliber where Re22 or Re25 did not produce excellent accuracy. The only time I've noticed temp sensitivity was when shooting above 85 degrees. In the last 20 years, I've noticed no change in velocity or POI using Alliant powders so long as temps were b/w 25 and 65 degrees.
I used to keep records after working up a load and hunting with it in various states at different temps, elevation, etc. Granted, the longest shot I've made prior to 2004 was under 450 yards.