Justin,
With that barrel length and on the Rem action I would use H4350 and work up from the Hodgdon load data online. Regarding the 6.5x55 I was loading for it is my shooting partners Tikka. We were able to go up from the max listed safely as those loads are limited to older Mauser actions. Just work up slowly one at a time in incriments until you get pressure signs then back off a little and start tweaking from there. H4350 is also the powder I use in my 260AI