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View Full Version : XS78 (QB78), not enough fun



Nickpan
26-07-2006, 07:29 PM
This rifle is a sort of stepping stone, between a loadsof fun co2 pistol and the new wave of gas rifles that take the big old Airsource Crosman 88gram style fatty co2 cylinders. The '78 takes 2 co2 12gramm bulbs, which go into the 'pcp looking' cylinder, under the barrel. The first bulb goes in pointy end first, ie, the pierceable bit first, and the second one butts up to it, with the small flat cap looking out. You then screw on the lid till it stops, count to 5, then undo it a tad. This unscrewing releases the gas, and you'll hear a quick hiss as pressure in the tube hits max (I lied about counting to 5).
This will give about 40 - 50 shots (I'm guessing) at the rifles top power, which is about 10ft lbs. I don't think the seals are soft, so there is no disadvantage to leaving gas cylinders in for extended periods of time.
That's the theory section finished.
I don't mind admitting that I didn't read the manual, so it was two bulbs in, screw lid on, fire. All the gas from one bulb hissed straight out in a couple of seconds, so then I learnt about the half a turn unscrewing. Next two co2s worked a treat.
No matter how I adjusted the rear sight, I couldn't get the pellets low enough to hit the target. Then I noticed a significant scuff mark, atop o' the barrel. I've a strong feeling that this barrel has had a whack, and is now bananana-ing upwards (I know how to spell banananana, I just don't know when to stop). I rang the supplier, who suggested I gently tighten the barrel ring. I gently tightened it, and then gently tightened it a bit more. The nut and bolt snapped, revealing that uniquely, it has a very thin bit in the middle, that really can only survive a gentle tightening. I bunged a scope on, and have solved the problem, as far as I'm concerned. In a similar blinkered fashion, a rattley car engine noise can always be cured by simply turning the radio up, or screaming constantly as you drive. There's two top tips for you.
The 3rd set of bulbs also seemed to work fine, and I fired a couple of dozen shots, the went to make a coffee. When I returned, all pressure had gone, all I got was a hammer twang. Where gas? Another couple of shots, but exactly the same, pellet sitting in barrel.
s h i t c a k e s .
I left it for a week, then grabbed a couple of bulbs of gas to start again, but I couldn't unscrew the lid. Strain, heave, something moved, the gun fired itself and the pellet snicked past my chinster pasty. Now, can we all learn a safety lesson from that please. Fiddling with the lid/cap, must have released another gas cylinders charge. Luckily the pressure was so low, that the pellet bounced off the inside of the conservatory roof, as if it had been thrown underarm, by a weak four year old. That had recently sprained its throwing arm.
I removed the co2 x 2, and put vaseline on the tips of a new pair. I daresay that is a foolish thing to do. Tighten tighten tighten (it takes some tightening), untighten a half turn. I fired a shot, and was greeted by a gentle hissing, heard from both ends of the barrel.
Is this the clear looking seal that is mullered, the one between charge cylinder and barrel?
Shall I put it all in the bin, sir?

airgun god
26-07-2006, 07:37 PM
nick stop playing with toys buy a proper rifle like my rapid :D :D :D

Kingplinker
26-07-2006, 07:43 PM
Nick ............................. what a great review . lmao you nutter :D

atvbmh ( all the very best medical help )

Dave

Nickpan
26-07-2006, 07:47 PM
Nick ............................. what a great review . lmao you nutter :D

atvbmh ( all the very best medical help )

Dave


Blimmin' gun. I've a feeling I'm not a natural, don'tcha know. :p

Kingplinker
26-07-2006, 08:00 PM
Blimmin' gun. I've a feeling I'm not a natural, don'tcha know. :p


No you are fine Nick ( in a mental kinda way )

If you like mate I could have a look at it for you or I could send it to a guy who loves messing with em ?

Dave

300zxz31
26-07-2006, 08:14 PM
Seems like you got a lemon. Mine has been 100% reliable. :)

lightning22
26-07-2006, 08:19 PM
It will either be the seal around the valve that has gone or the valve stuck slightly open.

Either way it's a valve out job.

Rich
;)

Nickpan
26-07-2006, 08:37 PM
No you are fine Nick ( in a mental kinda way )

If you like mate I could have a look at it for you or I could send it to a guy who loves messing with em ?

Dave
Shall I pop it up (FNARR!) one evening? Put that kettle on!

Nickpan
26-07-2006, 08:55 PM
buy a proper rifle like my rapid :D :D :D

Oh, alright then...how much do you want for it? :D

Smokeless Coal
30-07-2006, 05:12 PM
I've had one a few weeks no problems apart from that pathetic plastic barrel clamp, the barrel would wobble so I made a new one from steel. Polished and de-burred the works, set the adjustable trigger for very light let off.
Its accuracy needs a scope, with one on I get 1/2" groups at 25m, what more can you want from a 60 quid gun.
It's a diamond in the rough, a little bit of work and it goes quite well. Check for burrs around the bolt and crown. There is a nice site giving tune up tips look up qb78 tuning, be carefull its easy to take it up to 18ft/lb.

Old-gun
31-07-2006, 07:09 AM
.. Shall I put it all in the bin, sir?
no :eek: dont do that i will buy it off you for spare parts :D :D

cliff
.
.

ora8i
03-08-2006, 08:35 PM
I had one http://www.ora8i.rivington-riflemen.org/Rifles/XSQB78/XS78.html and had a lot of fun setting it up and messing about with it. In the end I set it to about 10.5 FPE to allow for heat drift. If you don't mind a bit of simple work then they are unbeatable value.


Ora

Smokeless Coal
04-08-2006, 09:41 AM
They are very popular in the States some even use them for competition. They are not consistent in quality control, you can get a lot of variation some are moderatly cruddy some are excelent.
I get a lot of variation of POI depending on the pellet I use, currently set up on Bisley practice for a 1/2" group, if I put in a dome head it shoots 3" high at 25m.
I get 35 shots at full power then about 20 with power dropping off trouble is to continue accurate shooting you want to lose the dregs of gas but theres no way other than keep firing and you have to put a pellet in each time or risk damage to seals.
Otherwise it shoots better than me so ideal for a beginer.

Gary C
04-08-2006, 11:07 AM
best review I've ever read.
Classic..

Glen M
04-08-2006, 07:55 PM
Bought one some time back, interestingly stamped webley Firebolt in .22.
This had a problem within a few weeks..gas just hissed out. But had to admit it was very accurate and nicely finished. Purchased from Ramsbottom, tried to buy seals but they threw a fit and insisted I returned it for a replacement. Who am I to argue.
Replacement one goes extremly well no problems at all. Nicely balanced light and very accurate. Great fun, plenty of tuning info on the web. You can run on 1 cylinder using a used one in first.

I also dry fire the rifle to empty it when the pressure gets low. However It's great fun still trying to hit targets as the trajectory gets more banana like...

In summary a real bargain, great fun but probably not one of lifes long lasting items. However there is plenty of info on the web for taking it to pieces and fixing/tuning. By all accounts it is a fairly simple job too.

croydonbrian
06-08-2006, 07:58 PM
have a look at this site for tuning info
http://charliedatuna.com/CO2TuneByCharlie.htm

Smokeless Coal
06-08-2006, 09:28 PM
I think a lot of that was plagerised from here
http://www.funsupply.com/airguns/qb78tune.html
Either way be careful with tuning as they easily go up to 20ft/lb. I think the best thing is just to de-burr around the bolt area to make it a slicker working rifle and spend a bit of time tuning the trigger for a silky smooth let off at about 1lb.
The barrel to tube clamp flopping about needs a good looking at to make it more stable. And the crowns are often burred which throws the shots out quite a bit.