Poster asked about a good on/off awhile back,. Have been using several RAP4 brass on/offs on some QB HPA conversions, but their current web site photos don’t show them as having a burst disk…ordered one… it does have the burst disk and the gauge. Have been using these with co2 bottles, 850PSI HPA tanks, and even a 1200psi HPA tank without a bit of trouble. to be fair, have used the Smart Parts on/off as well (the Al. version with no gaugue, just an on/off) without any problems either, but I like the RAP 4 version with the gauge for HPA.
So if you do try HPA on your QB79, the HPA bottle will have a 1.8K burst disk, and the on/off will have another, so with 2 safety valves, might be worth spending the $25 for the RAP 4 on/off (and the gauge reads the output pressure, so you’ll have a good idea what the HPA tank is really putting out).
From the top down: (can see the on/off knob, gauge, and burst disk):
From the side:
(The next two pixs will enlarge a bit if you click on them)
Used on a QB79 HPA:
And used on a Crosman 5mm 2250 conversion:
