Help QB79 Tune

[THE BRIT]

Hi Guys
Been looking at all the comments in the forum regarding the tuning of a QB79 fitted with bulk 9oz co2 bottle. CDT suggests enlargeing the inlet hole in the barrell.
Is there any reason why more holes could not be drilled, say at the twenty past and twenty two clock possition on the barrell, in your opinion would this have a similar effect as enlargeing the one hole in increase gas flow and power?
Currently shooting at 7 foot pounds, max in England is 12 foot pounds so I'm collating everthing before making any adjustments.

Look forward to your comments


also posted on China Gate

[shadow]

Hopefully one of our member's will jump in here with some insight on this, Mike M. of Flying Dragon Airguns would know I would think. Ed

[Big_Bill]

Hello Howard,

I moved your post to the QB-7X Gate, this should help you get the attention your post needs.

[ribbonstone]

It’s a tanker, so if you wanted to, could convert the valve to remove the pieercing  pin all together.  Could just ignore it, leave it in place, but ream out the hole it runs in (wouldn’t center a 12gr., but as you can’t use them, who cares?

Or you could drill some extra holes, making the ed of the valve look like a salt shaker, to let in more gas.

(Click pictures to enlarge)

[mikeiniowa]

Drilling holes in the barrel is possible, turn in a lathe a groove to the depth of the o-ring grooves, drill your holes and go if you want. If the existing hole is opened then it's not really needed, your only going to get so much gas out of the valve, I've done it on more than one and it may increase fps by 10 but not much more, the reduced back pressure allows more gas to be wasted....

[IJL]

If you port the barrel and bolt right (without EXTRA holes) WELL over 12 fpe is possible even on a 177. .22 hit harder. If you are going to play with one of these in the UK then make sure you have a chrono and test it with the heaviest pellets (Currently Piledriver 29.9 grains) at 20 dgress C.

Ian