QB78 help

[smsguitarist]

Hey guys

Hope you're all well and all!

I've been having some problem lately getting a grouping from my QB78DL :S It used to shoot sub 1'' groups at 30 yards and just lately it's just been doing absolutely rubbish. Seals are all good as i've changed them all but no improvement. Using the same AA field that gave me the good groups. Had a silencer clipping problem but that was fixed, the adapter had been shifted out of line in transit.

Could it be a crown problem? Valve problem?

Have re-polished internals to make sure they are smooth and no problem there but the groups are honestly about 6'' at 15 yards

Any help appreciated and i don't have access to a Chrono anymore so no 'tampering' that could improve power can be done really. Also the thread on the underside screw for the valve assembly has gone so that can't be removed not by me anyway i am ill equiped.

Cheers and all the best,
Lewis

[Hsing-ee]

Sounds obvious, but is the barrel seated properly in the action and is the retaining stud done up tight? 6" groups at 15 yards means that something is flapping in the breeze! I had a BSA Firebird that wouldn't group, just a tiny bit of re-seating of the barrel and it was spot-on. The pellets were being shaved by the loading block.

Have a look at the crown with a magnifying glass and see if you can spot any damage. But you would have noticed if you had damaged it surely? Try shooting it without the silencer just to make sure it isnt still a problem.

Other than that, is the barrel clean? Has it got some gunk stuck in it?

all the best with it.

[BeerJam]

Hi Lewis,

Much the same as has been said by Hsing-ee. Try the easy stuff first, check for any looseness at the barrel mounts and make sure that the barrel band is not too tight. Then take the silencer off and test. If that does not sort it give the barrel a clean and inspect the crown for damage. This can be done with a cotton bud by inserting it into the muzzle and slowly pulling it out, any burrs will catch a few fibres.

After that you really need to put it over a chrono to check the shot to shot consistency. If you were nearer you could borrow mine.

With the valve screw issue, it would be silly to start on the internals without trying the above first.

Good luck, I hope you get it sorted

Cheers, Mark

[smsguitarist]

Hey guys

Thanks a lot for the replies i really appreciate it! It's stuff i've already done but no harm checking again i suppose! If i'm still having problems i shall be posting right back here!!

All the best,
Lewis

[Gwylan]

Is the scope OK? try swapping it over. Does the barrel need a clean?

Gus

[smsguitarist]

Is the scope OK? try swapping it over. Does the barrel need a clean?

Gus

Hey Gus

Same result with my Simmons 8-point and JSR scope AO unfortunately. I'm cleaning the barrel and checking it over later in the week when i've got more time to do it properly.

All the best,
Lewis