Thoughts on .177 vs .22 air rifles

[Steve]

Shooting 0.177 pellets from a 0.22 spring powered rifle will wreck it rapidly. The rifle relies on the pressure in the cylinder to stop the piston from slamming into the end, a 0.177 pellet will not seal well enough to provide this "cushion" of air. Accuracy will be laughable, the pellet will not pick up any spin from the rifling and will be trying to tumble before it even leaves the barrel. If you absolutely have to use pellets of one calibre in another, get a pair of pliers and squash several pellets into a round ball that fits the barrel. You can do this with any lead you can find. A lead ball or cylinder can be "bumped up" to better fit a barrel by hitting it from both sides with metal rod whilst it is in the barrel, you could use this method to make a batch of pellets before leaving home, you need to take care not to damage your barrel with the metal rods.

Far better to buy a large stock of decent pellets in the first place.