I was thinking of buying this shock pump within the next day since I have the money and it's not as much as I thought it would be:

There's only one review and I can't get a ton of detailed info I want, like stroke volume, but it looks solid overall. I mainly want if because it can go to 600 psi, which is higher than most Amazon shock pumps. It might actually be the only one and with Prime shipping they almost have my money.
I plan on using it for future metal HPA guns (finally!) and for pumping guns past my limit of 120psi. I had a few questions though:
The newest gun I'm making uses (as far as I can tell) a brand new burst disk design and I have a limit of about ~250 psi (that's some thick pvc, yo). My biggest concern is the stroke volume on any shock pump. Will it take long trying to fill a 2"x30" pvc chamber with a shock pump?
Are there any floor shock pump designs out there, and would that even be worth it?
And no, for now I can't make my own. Thanks in advance guys, I hope you'll enjoy what I have to post in the next couple weeks.