When To Replace The C02 Cartridges In A QB78 ?

I have a new QB78 and put two cartridges in it and I have been shooting it forever it seems like but it keeps on spitting out the pellets. I can tell that the power has gone down but do I keep on shooting it or can I take the cap off the tube and let the c02 out or is that dangerous ?

Thanks Bill

What distance are you shooting at?  I have to shoot at 10 yards in my basement.  For that distance, I get 130 shots out of my QB78.  Last 10 shift POI, although they still group fairly well.  Mine is not tuned for power, but for reliability.  It is a .177.  I suppose I should really stop at 120 count, but since I am not shooting competition, I don't care that the POI shifts left and down.  I probably would have to change powerlets sooner if I were shooting at longer ranges.  Obviously your gun isn't tuned for power either, else shot count could be as low as 30.  Maybe less.

Can't tell you how many shots you will get from a bulked rifle.  Definitely a lot more than from 2 powerlets.  Should be in the 100s for the type of tune you and I have.  As always, power tunes use a lot more gas.  Sorry, can't have both power and tons of shots as far as I know.

You can tell from the sound when it is time to stop shooting pellets.

[IJL]

Bill, out of the box 78s usually shoot 70-80 pellets before you start to hear the hammer spring twang, then you are running low on gas. I doubt you will be able to shift the end cap when there is liquid CO2 on board but there is a small bleed hole that will let excess gas escape after you back the cap off 4-5 turns. Wait until it stops hissing before you remove the cap fully. I've never counted the shots from a bulked rifle but a lot depends on getting the full load in before you start, there is a process of chilling the tube before you decant the liquid CO2.

Sounds like you are enjoying it though

Ian