Wait a min! You work at a fire station? Then by all means use HPA. From what I have heard you can fill off the whip if the pressure is correct. I would get a 4500PSI tank with a good regulator if you go that route. I have a cross fire tank and it is awesome. I have 7 other various HPA tanks and none of them even come close. Something that I just learned is that the HPA tanks reg has a break in period. This means that as you use it, it will become more consistant. From my understaing this is at around 2000 shots. Now the advise from Duff will work as well and the break in period would be the same for the palmers stab. The truth is you have C02 and have HPA available at work. Both ways are workable. I say flip a coin. The catch is get something that is of quality. If you dont you will prob end up buying loads of stuff that doesnt quite work right.