After lending a new comer the QB78 last weekend Her father asked if it might have come off the reg while She was shooting the match and well no, it, shouldn't have? But I checked and it had , awful thing to hand a new comer. It had a tiny leak, 2,000psi in 2 (?) weeks but had always shot a full match or gone squirrel hunting just fine, now absoultly time to tear into a professional built/modded QB I'd never been in before.
The adaptor screw on the left side was the main culprit ( I thought ) and note the screw is much heavier grade and placed further back than factory QB sthuff
On the adaptor you can see where this one is drilled for the new anchor screws compared to the factory screw holes much closer to the end, standard PB o-ring
Barrel must be removed to expose phillips head screw under pellet tray ( machined into barrel )
and the rear trigger group screw goes through the trigger housing/main tube end cap and receiver end cap holding the top end on
shows the added valve rention screws and the stock bolt going into the roughly half " think valve backer (?) ( valve would have to push said part out to move and give striker/hammer something to run into ??? technical huh ?)
both the valve body and receiver have been milled slightly to accept a good seal with poly tubing and the TP is slotted .
After removing everything in the way I used a Bic pen to press the hammer for degassing, just took a gental pressing
The valve is a two halve type and you must unscrew the front half slightly to relieve pressure on the oring so it will slide forward it requires a special tool such as a screw driver that fits or a section of 1'8" bar stock in this case, took about 1-1/2 turns to loosen
Note the valve is slotted ( only a small hole in front from factory ) this is THE QB and many other ( 909 big-bore ... ... ) airguns. And again note the extra retention for safety screws even though I run 1,000psi and the valve port milled to fit poly line transfer port tubing
Factory metal stem next to longer custom delran stem in the valve.
So the tank adaptor o-ring would be super easy though only TINY bubbles showed with windex. After removing the breech I sprayed the exhaust port, OH MY ! Okay all the way in. Removed the valve and the valve body o-ring was slit ( sort of but I've learned if I can see Anything on an o-ring it is bad enough for me) , and, the valkve stem was gritty and would not pull out of the brass body. Shucks.
I did have a factory stem I could try but my stem is longer and uses a felt debouce thingy and ......... . I used some Mothers chrome polish and slowly twisted and pulled and pushed very gently and in a few minutes the stem slid cleanly out just shaking it. It took a good bit of cleaning to remove the residue using Birchwood casey barricade, then well dried and re assembled. Wasn't all that sure it would hold for even a minute but it held 2,000psi over night and I took a few shots over the chrony today.
With JSB 7.9
H-940
L-927
AV-932
ES-13
Sd-3
right hwere it should be though I slightly smashed the pellet shooting the lowest number so maybe a bit tighter numbers?
10.3g JSB
Av 855.
To windy for group testing but it normally shoots well enough to win a competition if I just hand it to a good shooter.
Now to get some proper numbers and ranges and a card made so that when I lend it out I am not ruining someone's otherwise great day. You have to be nice to the new people and handing them a rifle that's out of ( useful - but they wouldn't know the difference ) air. Then again if her boyfriend would just buy her a TM1000 she would be all set to go, maybe I helped? Either way the QB is back and I personally recommend them to people new and old.
Trigger group for those that haven't seen one. Engagement can be taken WAY down safely.
John
The adaptor screw on the left side was the main culprit ( I thought ) and note the screw is much heavier grade and placed further back than factory QB sthuff
On the adaptor you can see where this one is drilled for the new anchor screws compared to the factory screw holes much closer to the end, standard PB o-ring
Barrel must be removed to expose phillips head screw under pellet tray ( machined into barrel )
and the rear trigger group screw goes through the trigger housing/main tube end cap and receiver end cap holding the top end on
shows the added valve rention screws and the stock bolt going into the roughly half " think valve backer (?) ( valve would have to push said part out to move and give striker/hammer something to run into ??? technical huh ?)
both the valve body and receiver have been milled slightly to accept a good seal with poly tubing and the TP is slotted .
After removing everything in the way I used a Bic pen to press the hammer for degassing, just took a gental pressing
The valve is a two halve type and you must unscrew the front half slightly to relieve pressure on the oring so it will slide forward it requires a special tool such as a screw driver that fits or a section of 1'8" bar stock in this case, took about 1-1/2 turns to loosen
Note the valve is slotted ( only a small hole in front from factory ) this is THE QB and many other ( 909 big-bore ... ... ) airguns. And again note the extra retention for safety screws even though I run 1,000psi and the valve port milled to fit poly line transfer port tubing
Factory metal stem next to longer custom delran stem in the valve.
So the tank adaptor o-ring would be super easy though only TINY bubbles showed with windex. After removing the breech I sprayed the exhaust port, OH MY ! Okay all the way in. Removed the valve and the valve body o-ring was slit ( sort of but I've learned if I can see Anything on an o-ring it is bad enough for me) , and, the valkve stem was gritty and would not pull out of the brass body. Shucks.
I did have a factory stem I could try but my stem is longer and uses a felt debouce thingy and ......... . I used some Mothers chrome polish and slowly twisted and pulled and pushed very gently and in a few minutes the stem slid cleanly out just shaking it. It took a good bit of cleaning to remove the residue using Birchwood casey barricade, then well dried and re assembled. Wasn't all that sure it would hold for even a minute but it held 2,000psi over night and I took a few shots over the chrony today.
With JSB 7.9
H-940
L-927
AV-932
ES-13
Sd-3
right hwere it should be though I slightly smashed the pellet shooting the lowest number so maybe a bit tighter numbers?
10.3g JSB
Av 855.
To windy for group testing but it normally shoots well enough to win a competition if I just hand it to a good shooter.
Now to get some proper numbers and ranges and a card made so that when I lend it out I am not ruining someone's otherwise great day. You have to be nice to the new people and handing them a rifle that's out of ( useful - but they wouldn't know the difference ) air. Then again if her boyfriend would just buy her a TM1000 she would be all set to go, maybe I helped? Either way the QB is back and I personally recommend them to people new and old.
Trigger group for those that haven't seen one. Engagement can be taken WAY down safely.
John
