I'm not sure I understand your question. You had me until it came to the hundred rounds statement. You say you shoot once a week with the .270 but 100 rounds a year?
IMHO, No way sell the .270 for $100, keep it for that kind of money. If range time per dollar is the issue, buy a quality .22 LR and shoot 100 rounds a week. A .223 will save some money on ammo, (if you can find it), and is a nice paper round, but like I said I'm still unclear as to exactly the problem or issue.
Oh yeah, WELCOME TO THE FORUM!!