1911 hammers don't bounce and there's enough inertia/force between the hammer strut/spring/hammer/firing pin to keep the pin protruding from the breech face until the slide moves back enough (firing pin stop radius interacting with the base of the hammer face) to push the hammer out of the way. It takes a little more than 1/16" of rearward slide movement before the firing pin is able to retract flush with the breech face. In that same amount of movement, the barrel feet begin to slide off of the slide stop pin and the rear of the barrel begins to tilt downward.
Now, notice two things with Brad's cartridge: The firing pin indent is low, and the extruded part of the primer is centered. If the firing pin is a decent fit in the bore and the tip isn't bent, this means the two events took place separately, or the extrusion happened as the slide began to move. At about the point that my barrels drop the distance of half a firing pin dent, the firing pin is still very much protruding and in fact will leave a little comma swipe coming out of the firing pin indention (probably because the barrel foot slope is too steep on the after market barrels, or the radius is too large on the firing pin stop and the slide isn't pushing the hammer back soon enough). So the firing pin, in proper effect, supports the very center of the primer cup at peak pressure and keeps cup material from flowing back into the firing pin hole.
If cup material is flowing, either the pressure is too high, or the firing pin is pulling out too quickly, as in right after the primer charge goes off, or the cup material is weak. As Bill and I have both already said, the flash holes on lead-free Federal brass can be huge sometimes and over-pressure the primer cup, but you should have seen that before with this load. Did you recently add a box of range-pickup Federal with extra-large flash holes to your rotation?
The barrel feet and firing pin stop have likely remained constant for some time, so that wouldn't explain only 25% of the primers extruding.
The load, presumably, has remained constant. Red Dot doesn't meter for $^#% in my measures, I never worked with Promo so I don't know if you're getting bridging and occasional heavy charges or not. Red Dot is also very spikey like Clays, but should be fine for 200 SWCs. The primers were consistent before....but up to a point. If you use a Dillon, you use primer tubes, which means there could be a bad sleeve of primers in the mix and depending on how you picked them up int the tube or mixed sleeves and tubes, there could be any order of primers from a given 2-3 sleeves in there.
All things considered, I think the most likely scenario is a bad batch of primer cups or lead-free flash holes.