You could do a lot worse than a Diana 34. It's generally a pretty accurate rifle. If you had it scoped, I suspect the scope may have been the problem, not the gun. Spring rifles tend to be very hard on scopes, especially the inexpensive ones. You really need to use a quality scope thats rated for use on heavy springers if you want it to last. Springers are also hold sensitive. If you sight the gun holding it one way, then come back a couple days later and shoot it holding it somewhat differently, it would appear that the sights had moved. It doesn't take a lot, just holding the forearm a bit more forward, or putting the thumb of your trigger hand in a different spot is sometimes all it takes. The trick is learning how to hold the gun properly, and remembering to do it the same way every time. No spring rifle, no matter how good it is, will be accurate until you learn how it use it properly.
Then theres the pellet thing. Not all pellets are equal. The gun may be very accurate with one specific type of pellet, but will scatter another type all over. You need to try a bunch of different pellets to find out what works in your gun and what doesn't.
