Not even the concussion or pressure from the rounds hitting the plate? That’s some significant force.
My AR-10 turns my shoulder to jelly. Of course...my shoulder is already a victim of socket misalignment, bone-on-bone contact, and arthritis. Still a fun gun to shoot though.
The plate spreads the impact over the whole plate so the force at any one point is much less resulting in more of a hard shove than a punch. Many soldiers and Marines have been struck in the armor plate and have gotten back up and continued to fight.