Qb79 premium combo package?

[Raden1942]

Hey guys this qb79 rifle at airgun depo says its already equipped with a bulk fill co2 adapter to prevent the bottle from touching the barrel. Is the only thing id need to convert this to hpa a ninja regulator and bottle rated for 3000psi? I realise id need the reg to be set to safe pressure but am i missing anything? Would it need a heavier spring or anything else? Thanks I saw this gun and thought it seemed like all it was missing is the bottle. 

 

[biohazardman]

Yes, looks like that that is all you would need to shoot at co2 pressures. Would make a good shooting winter gun with no loss of power because of the cold. You would need a heavier spring and or hammer spring adjuster to shoot at higher than co2 pressures. But be careful with the pressure though as bad things have and do happen when one exceeds the limits.

 

[John "spysir" Blount]

Wow pricey.

What is this " Air Venturi CO2 Adapter " they speak of? Would it be the EXTRA drop down which allowed Co2 bottles over 2" to fit the standard QB? I only have an old QB79 so???

A regular qb79 will takes any tank under 2" dia, a Ninja 13ci fits right on. Hammer spring is already too heavy so if on HPA and you stay under maybe 1,200psi your good to go. If the internal fur ball has been removed from the valve 850psi is all you need for 12fpe. 

I know Co2 tanks got slightly larger some years ago and figure this is what the mention adapter is for.

A person who enjoyed DIY could get a $79.00 QB78 and a $12.00 drop down from umarex and have a 79 for under $100.00.



Great little rifles no matter.

\

John

 

[nervoustrig]

x2 on what John said on the cost and the drop-down adapter being unnecessary for most 13ci HPA bottles (e.g. Ninja).



I also agree about the factory hammer spring in the QB78/79 being good for roughly 1100 – 1200psi. Meaning you’d want to shorten it (or reduce its preload) if you plan to run a standard Ninja bottle at the factory preset of ~850psi, otherwise it will be wasting air and consequently have a louder report).



Shortening it is easy…just use an emery wheel in a Dremel to cut off half a coil at a time and then check it over a chronograph. Keep going until you see a slight drop in velocity. If you accidentally shorten it a little too much, simply add a washer or two to the spring guide to bring it back up.



The other way to go about it (reducing preload) is better but it requires drilling and tapping the end cap for a screw. It serves as an RVA (rear velocity adjuster) so you can dial in whatever preload you need. This approach pays dividends if you will be tweaking in stages. I have pictures and description of this modification and others related to tuning to a higher power level in this writeup:

https://www.gatewaytoairguns.org/GTA/index.php?topic=85896



I’ve worked on quite a few QBs so just let me know if you have questions.

 

[Raden1942]

Sweet guys. How many shots would you guess i could get with the 13ci bottle at 1100 psi with screw adjuster tuned up to give me 16 fpe? I can handle 12 bit would much prefer 15 or 16. That extra little bit goes a long way flattening out those heavier 22cal jsbs. 

 

[nervoustrig]

Shot count would be on up there. 16fpe is a pretty modest energy level in .22 cal. A JSB 15.9gr at 675fps for example.



With a 13ci tank, you’re looking at anywhere from 100 – 150 shots on a fill. The 100 shots is with an efficiency of only 1.0fpe/ci which is pretty poor for this power level. The 150 shots assumes an efficiency of 1.5fpe/ci which is very much achievable with a simple RVA as described in the writeup I linked. You can improve that even further with an SSG that prevents hammer bounce.

 

[Raden1942]

Hey spysir do you have a link where I can buy a umarex drop down? I looked on thier site and am having trouble. I found the air venturi and archer ones but no umarex. Thanks.