Does the QB78D or AR2078A have a dovetail for a scope?

[rsterne]

Depends on what you want to do.... If you want to bulk fill the tube (limited shots) you will need a new front cap with fill fitting.... You can attach that to a larger tank with a hose for more shots... If you want to mount a tank ala QB79 style, you will need the tank block (prefereably with extra screws for safety) and shorten the tube and drill to mount the block....

Bob

[SeanMP]

Actually I would advise you to avoid the full length mounting rail. It would very likely shroud or completely block the loading ramp area. There is no kick to these rifles so using a bomb proof rail isn't necessary. In fact when I mount a scope for testing a barrel or some pellets I often use 1 screw per.

To convert to bulk C02 you need this thing
http://scopesandammo.com/storefront/...-end-cap-p-647

To convert to HPA it's simply a matter of stripping the gun and removing all traces of lubricant, relubing with silicone, and checking that the stop block is tight to the valve. And of course you need the item above to fill it as per C02

[AirGunEric]

HPA, if using the stock tube, should not be over 1500psi- there are no tests on the QB tube burst pressure I am aware of- but they certainly aren't 3000psi tubes.

[rsterne]

If using regulated HPA, protect the gun with a 1.8K burst disc on the downstream side of the regulator.... otherwise the gun could see 3000 psi (or 4500 if you are using a 4500 psi tank) if the regulator bypasses.... The 1.8K burst disc will limit you to 1500-1600 psi maximum otherwise it may blow the disc....

Bob