I agree with colorado above. There are lots of great cartridges for a beginner rifle. Personally, I am a fan of the .308. It is a very versitle round, thatgives you lots of options. But then so do many others. To be honest, I really don't think there is a truly RIGHT answer.

you mentioned the .270 and had good luck with that. If you liked that then buy one.

Good luck to you .