500 for a military press would have to be some kind of record. To stand with 500 pounds and press it above your head id crazy. Now if you are seated I can see it…but I would be willing to bet the back would be arched and the ROM wouldn’t be from bottom to top. When the back is arched it almost turns into a incline bench press with an arched back. I only say this b/c everytime I see someone go heavy on any kind of shoulder press this is what I see…never keeping their back perfectly straight and a full ROM. Either way any 500 lbs press is some serious weight and I wish you good luck and hope you don’t get hurt.