If you've tried to use 800X in a 9mm, you'll clearly see that some powders may perform great, but meter terribly and don't work well with powder measures. That powder can vary by more than +/- 1/4 grain which translates to a 1/2 grain spread. When hand trickled, it performs great with single digit extreme spreads and low single digit SD's.

Other powders such as Titegroup meter very well with metallic powder measures, but I've found that it bridges in my Mec 9000. After hand weighing a few box loads and getting great performance in skeet and trap, I loaded a few boxes with the proper charge bar bushing and wound up with alternating bloopers and near double charges. Fortunately with only 3/4 oz of lead to push, the really hot loads just felt like a 3" magnum load. I disassembled the rest of the loads and will now only use Titegroup in hand weighed shotshell loads.

I've never experienced bridging before but with a super dense powder that clumps in a long tube powder drop, now I have.