I built my 6.5x284 on a long action , it feeds the 140s great.
I have a 6.5-284 built on a LA Rem 700, started life as a 30-06, and a 6-284 built on SA Rem 700, started life as a 22-250, I've never had a single feeding problem, ever, with either one.
I've read many times where people say the 6.5-284 feeds bad so I guess there must be something to it but I've never had a single problem with how either of mine feed.