QB57 Tune - How I did it by John Giglio
Our first post of 2011 comes from a customer. John Giglio purchased a QB57 from Archer Airguns and then tuned it. This post describes what John did, in his own words.
NOTE: As with any work on spring-powered air rifles, you need to have an airgun spring compressor and know how to use it - as John obviously does. If not, considerable danger can be caused by the gun's mainspring if improperly removed.
John writes...
I purchased a QB57 a few weeks ago from Archer airguns and thought I would add a few comments to the information already available on the web. 
Overall I agree with Stephen Archer’s assessment of of the QB 57 as a sturdy and accurate air gun. It is a comfortable gun to hold; however, the combination of the extremely long trigger travel and the short length of pull created by the bullpup stock combine to make firing the gun feel rather awkward. I find that my finger simply does not fall in the proper position to allow for the correct trigger squeeze. I think I may have to add a butt extension at some point, as Stephen did with his own QB 57.
Also, because one’s ear is directly next to the receiver, the gun seems startlingly loud, and this can interfere with accuracy as well as health. I really suggest ear protection. Despite these facts, I enjoy shooting the gun, and, as Stephen says, it is a unique and interesting addition to an air gun collection.
I did a basic tune up on the piston, compression chamber, etc.. The chamber itself was surprisingly smooth for a Chinese gun, and I ended up not needing my brake hone at all, especially with the synthetic seal. As firing – despite the long pull – was fairly smooth I got lazy and left the trigger and sear alone. I only gave what areas I could reach a quick degreasing, and a tiny touch of moly here and there.
Although there are no complete tuning guides on line for the QB 57, as there are for other Chinese guns, you can find Russ Sauer’s B-3 tuning guide and CharlieDa Tuna’s Fast Deer guide easily enough, and between the two you pretty much have the QB-57 covered.
One thing that is different about this gun is that when removing the block that holds the spring in place (in your spring compressor for sure with this gun), you don’t just knock out a pin to free it up; there are two screws on either side of the receiver that hold it in place. Remove the one behind the sear first; it is a bit puzzling because it is held in place with a square block rather than a slotted, Philips, or hex head. Nevertheless, if you just fit a wrench or pliers to this square and treat it like a bolt it unscrews just fine (see pic). Mine was in really tight and at first I wondered if I had things right. After you remove this screw, take out the slot-headed screw on the opposite side, and then you can back your block and spring out. 
Removing the top screw from the receiver. John's spring compressor is in use here.
Removing the lower retaining screw from the receiver. Action still in the spring compressor!
The only really new thing I can add to tuning this gun is you might want to fit some washers on either side of the cocking arm pin. I didn’t like the amount of play in the arm – it really seemed to flop around – so I found appropriate sized steel washers to fit on either side of the pivot hole in the arm, and that tightened things up perfectly. I did, however, have to grind them down thinner, as I couldn’t find ones thin enough to work. I added a little moly when fitting it all together.
Arrows show where John fitted the washers.
I also took a little time to sand out the cut-out indentations in the fore-grip, which had been left rough and partially un-stained by the factory. I re-stained these bits with some mahogany Minwax when I was through and it helped with appearances. Areas that wouldn’t take stain because they still had some Chinese varnish soaked in I hit with a brown sharpie marker.
Lastly, I used a suggestion Mike Melick posted long ago and went over the stock with some Carnauba wax. This did wonders for my QB 78, and it helped out with the finish here, too. It helps even out the finish of the stock, as sometimes there are variations in the level of gloss or dullness on the same stock of these Chinese guns.
The QB 57 is unique in that it seems to prompt many variations on how people fit it out with sights. The scope rails are too far from the eye to simply fit a scope the conventional way: your eye will be simply too far away and you will have to thrust your head forward while shooting. Stephen Archer has solved this problem by offering a long eye-relief scope which is also nicely compact; however, it doesn’t have AO, which is something I was set on.
I was pleased to find that, despite its “compact” size (the gun is actually surprisingly big and heavy when assembled) the QB 57 can easily take a full-size scope and remain balanced. The longer-tubed scope gets the eyepiece closer to where it needs to be than if you used a Bug-Buster or other compact AO scope. I gained a little more by adding a pair of Leaper’s offset-mounts. They were only $13, and when combined with the Leapers inexpensive 4 x 32 Golden Image AO scope it makes a nice compliment for a gun in this price range. The set-up isn’t perfect in terms of comfort, but it’s close enough to work for good shooting.
And this gun really can shoot. My tuning helped make it less harsh, and made cocking so much more pleasant. I was surprised how quickly the gun settled down: after about fifteen shots after tuning I shot the group below: at ten yards, four of the five pellets went into one elongated hole; the other probably would have, too, if I had shot better.
Overall I think you can’t go wrong with this gun, especially if you have a lot of conventional rifles or pistols and would like a change of pace.
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