QB79 HPA conversion question

[JonnyReb]

  Hi guys
  If you were to take a stock QB79 and convert it to HPA, am i correct that all it takes is the purchase of a ninja or JDS regulator and 13/3000psi tank, air the tank to any pressure up to 3000psi and screw it all together with no other fitting or adapters required? The regulator will automatically hold the incoming pressure to 850psi(ninja) or 1000psi(jds).  Am i correct in all this? Anything else to buy? Thanks,  J

[rsterne]

Those are the only parts you need.... but PLEASE make sure the regulator has a 1.8K burst disc installed on the downstream side.... I know of at least one gun where the regulator failed suddenly, there was no such burst disc, and the gun was pressurized to 2600 psi.... The screws securing the tank mounting block to the end of the tube sheared, the holes (which are too close to the end of the tube) bulged and nearly tore out.... The tank/regulator/tank block assembly blew off the end of the gun and went spinning across the shop.... Moments earlier, it would have hit the person holding the gun in the head, but fortunately no one was injured THIS TIME.... The stock screws are very soft, and it would be a good upgrade to replace them with harder screws.... although then the holes in the end of the tube would likely tear out anyway....

CO2 can reach ~1900 psi at 120*F.... so to think that a gun failed at 2600 psi shows how little safety margin there is on a QB79.... My guess is that they designed it with about a 3X safety factor for the usual working pressure for CO2 of 850 psi at 70*F.... and ignored the fact that even CO2 pressure can be well over double that on a hot day or in a car on a sunny day.... 

This conversion is possible, and frequently done.... just make SURE that the gun is protected by an 1.8K (ie 1800 psi) burst disc....

Bob

[JonnyReb]

 Thanks Bob, i'll make absolutely sure there is a burst disc in place. Appreciate the confirmation,  J

[SciGuy]

J, The Ninja 13ci 850psi regulated tank combined with a RAP4 On/Off valve is a near perfect way to move a QB-79 to HPA.

[jonnnyboy]

Jeff, I second Mike's suggestion.  The Ninja 13ci tank and regulator plus the Rap4 on/off will get you to where you are wanting to go.  With a little valve work and a new breech seal made from icemaker tubing, that QB79 will be ready for the woods, backyard or the range.  Enjoy.

joe

[JonnyReb]

 Thanks Sciguy and Jonnyboy, thats just what i'll do. I appreciate the info and will put it to good use. J

[JonnyReb]

 Hey just curious but can that same 13ci tank also be used to refill another pcp in the field? Say a disco? What coupling is used to attach to my tank line for refills?  Thanks J

[jonnnyboy]

JR, the output of the tank is only 850psi so the answer is probably no.  You could rig it to get air out through the asa fitting on the tank but the output is limited to the normal co2 pressure or approx. 850psi.

joe

[JonnyReb]

 Thanks joe, that makes perfect sense.  J