catapult hunting?

[Jack]

Wrong and right...
Bang on right that its not illegal to trespass on private land (try it on government or nuclear sites and its a different story) but I'd say wrong on the catapult as it can be used as a deadly weapon for just having it about your person and conviscated or as you mentioned going with intent.
Also it IS illegal to trespass and could end up doing porridge if you have a weapon ie: "armed trespass".
The armed police that where called out in both mine and Paul's examples would have been responding to a "potential" armed trespass. Given that they can arrest you for carrying a deadly weapon, a catapult, if they saw or suspected you of carrying that on land the owner wanted rid of you from then your numbers up!

It's not good practice going on private farmland or otherwise without permision and shooting game, not only is it taboo and gives the shooting community much unwanted bad press but its the easiest way of getting a 22LR through the chest by accident.

I'd not be so worried if you where out in the middle of nowhere, no risk of dog walkers, game keepers etc in some disused wood/wildland (not belonging to national trust) for some plinking with the catty but not live game.

If your not already then get proficient enought to 100% knock tin cans over at ten yards, then lighters, then polos.
Then take that method out to 20 yards and so on...