I started out reloading 70 years ago for my first center fire rifle, a model 92 Win. carbine chambered for 38-40. Within a week, I got my first lesson as to the power of a large rifle primer. It seems I missed one case when throwing the charge of #6 pistol powder and when "fired" the lead bullet was driven somewhere close to 4" down the barrel by the primer alone. I had a newfound respect for that tiny component which has lasted a lifetime.
Did it stop me from removing live primers from cases? No, but as the kid in the video said, "I have a plan." Is it a good plan? Well, most of the time.
One thing to take into account is that when a primer explodes, something or somethings gonna move. The explosion will take the path of least resistance.
Contained in a chamber, as with my first experience, the bullet was the only choice.
I've never set off a primer (crimped or otherwise) while pressing one out of a case in a die, but I'm pretty sure that the blast would drive the unsupported primer downward and, depending upon the press design, could endanger lower extremities exiting the press. If this is the plan, I'd look over my press and determine the likely trajectory should a detonated primer result.
I have removed a number of live primers with the old fashioned hammer and punch. Only ever had one crimped small rifle primer detonated, and since I always expect it to detonate, take steps which prevent(ed) any serious consequences.
Using my decapping anvil, wearing safety glasses and a heavy leather work glove to hold decapping punch/case, I tap gently (much lighter taps than used on inert primers) until primer(s) removed. I remove each live primer from the anvil & do not let primers accumulate in the anvil.
The day the SR primer did detonate, I felt nothing through the leather glove, as would be expected. The primer, however, being the lightest unsupported component, was propelled with sufficient force to embed itself flush into the 3/4" plywood bench top,
where it still resides as a warning to respect those lowly primers.
Regards,
hm