QB78 pull down help

[Dukemeister]

Hi forum...
Went to shoot my 2078 this am, and it was bone empty... so it must have vented what little I put it away with a few days ago. So, I decided the time had come for a tear down and polish and to install those new seals Eric sent with the rifle. 3 questions:
1. What size hex key is used on the barrel setscrew? none of mine seem to fit it.
2. In the replacement seal kit there is one "white" colour O-ring where does it go?
3. The transfer port seals are less than square... how critical is the "squareness" of the cut... should I try to straighten them up?
Picture below:
QB.jpg

[AirGunEric]

I believe the hex key is 2mm (could be wrong on that one, don't have one handy). The white o-ring is for the Co2 cap (it is polyurethane not buna, so it is more heavy-duty and won't disintegrate as quickly being rotated when removing the cap)- however it may seem like a bit of work to get it on initially- it will stretch somewhat and can be 'rolled' onto the cap without causing any issues, and the transfer port seal is thicker than the stock unit and compresses when installed, so absolute squareness is not required- just be sure to tighten the breech to the tube completely to allow it to compress- it will eliminate what is often a leaky area on this rifle. If the rifle bled down over time- be sure to take the valve apart and be sure it is clean- what with the QB's sometimes having some "grit" left in them- if it ends up in the valve, it won't seat completely.

[SeanMP]

Hi Duke

The white seal is for the valve cap (sorry tube cap)

The transfer port seals are less than critical. give them a light trim with an exacto to square them off. As supplied there is more than enough squish. I machined a small flat on my breach so I could use use white 1/4 tubing

I will go measure the key

[Dukemeister]

Thanks, Eric. The rifle holds fine when full.. but I shot it down close to empty.
It will get a clean out anyhow once I get that barrel off. Cheers.

[Dukemeister]

Merci, and thanks too, Sean.
I found a teardown guide, and it says hex key is 2.5 mm - what are the chances i have one....?

[SeanMP]

0.098"
or
2.48mm

[Dukemeister]

hehe, right on the money. Sorry for making you measure (my bad).

[Dukemeister]

0.098"
or
2.48mm

Doh, mine seem over sized. I have tried a 2.5 mm it just spins and doesn't bite into the hex, 3 mm is too big and doesn't fit~
On the bright side, my custom oversize bolt handle fits nicely!
bolt.jpg

[poil27]

try sae sise it could be some where around 1/8 3/32

[SeanMP]

Well that totally bites.

I don"t suppose you have one of those screw driver bit assortments that 8 million different sizes of small allen drives?