300 bar bottle only for m3 and maverick???

I see some people are getting their hands on the new fx 300 bar bottles for their impacts m3 and maverick. What I want to know is, can we use the 300 bar on mk1 and mk2 impacts? There are many 300 bars fill airgun out there with only 1 reg. So 300 bar bottle isn't limit to dual reg only right? I want to be able to use the 300 bar on my mk2 impact for more shots per fill. Can I or do I need to go out and get a m3? o_O

Can older models of FX products be retrofitted to 300 Bar?
 
Here's a screen shot of info on Huma's website on the reg above. Shows 250bar max

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