Under the right conditions even so called temp stable powders can give pressure spikes. Benchmark is one of those as I stated earlier. MD has said many times that they are stable only when used in their designed application, different cartridge or bullet can change that.
I really don’t chose a powder just because it’s supposed temp stable.
Now as far as baffles, my reasoning is if you have ever watched the effects of a small outlet hole on things such as grain bins, coal hoppers or lots of other granulated products in a bin or hopper, they usually have knockers, vibrators, baffles or a combination to stop ratholing, clumping or bridging.
By using the baffle it allows for a stable level and weight on the powder feed. This helps in getting consistent drop charges. Now it’s not really super beneficial with ball powders, but still if you have consistent level and weight it will make drop variations minimal.
They really do shine with flake and coarser powders especially in the Uniflow for the same reasons. A quick test is fill your hopper then drop 25-30 charges back into the jug, weigh #1 then #30 if ratholing or bridging is going on the charge weights will start getting lighter. Then finger snap the hopper a couple of times the first charge will be heavier, while the second should be back to nuts on, or at least it’s always has for me.
Baffles when properly set cures 99% of that.
For those who like to tinker or a baffle isn’t available for your hopper go here, I made my own for an 80’s vintage Hornady measure.
https://castboolits.gunloads.com/attachment.php?attachmentid=26566&d=1288932878
