I have B2's in both calibres and I can tell you now that the .177 is way better than the .22
A 100ft/s may not be no big difference when the gun is shooting over 700ft/s, but at that low velosity it is the difference between a kill and a bruise. My .22 was shooting fine for awhile, but unless you want to do a tune after every tin of pellets, stay away. The poor quality springs just can't cope with the heavy .22 pellets. It drops down to under 400ft/s every once in awhile. That is hardly enough to make a hole in a beercan at 10m. I'm actually going to give mine away, because the thing just spoil my day everytime I shoot it, and as long as it is lying around, I will try to use it.
No use in putting in a bigger spring either... the trigger WILL FAIL, that I can guarantee you.
Actually, now that I'm thinking of it... I'm getting rid of all the B2's. They are crappy little guns.
We don't even sell them at our shop anymore. It's the type of product that can ruin your reputation.
The few that we have left, we'll probably give away for free.
We have other Chinese rifles like the QB36-2, the QB23, QB18 etc. Don't know if you have those over there, but here the QB18 or QB23 is about $55 (rifles are expensive here) but it is way better than the B2 ( at about $35 ). The wood finish looks nice. It has a proper recoil pad and sights. Accuracy and quality is very good for a cheapy. For a few dollars more the QB36-2 is the best rifle in it's price range. Untuned we get over 850ft/s with Pro Magnums and just over 1,5" groupings at 65yards.
The Chinese improved their quality a lot, but the B2's suck. I'm not happy about the B3's we have here either. Most of them are finished after about 1000 shots.
http://all-about-airguns.co.za/qb.html