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I would suggest less poundage first. As far as arrows go Easton makes a good arrow and you won't have any issue making the 6 grains per pound. Easton axis or the FMJ would be good choices for elk. Lots of guys shoot gold tip, though they seem to run lighter and you might run into trouble making weight. If you want something economical try bemans. For a hunting arrow I would also look at an arrow that has a straightness of .003 or less. As far as spine goes I would error on a stiffer shaft as well. Cut the length so that it is even or flush with your riser at full draw, a pro shop should be able to help you with that. What bow did you buy?
Buck rub (and anybody else interested), here's a link to what I think is one of the best threads on hunting arrow selection out there. It was launched by a hunter that goes by the name of Beendare on a few of the hunting forums and this cat has some seriously good perspective on what a hunter should consider when building their hunting arrows. Take a peek and see what you can glean from it. v/r RJhttp://www.wapititalk.com/Hunting/viewtopic.php?f=14&t=8504
I have a similar setup to yours and shoot a .300 spine black eagle rampage. The lightweight shaft and the 56 gr outsert give you a higher FOC and better penetration which is key for big animals. My arrows are cut 30" from the valley of the nock. 440gr finished weight and .001" straightness. I don't think you need a 250 spine for your setup and if your are hunting elk I wouldn't want to drop your poundage IF you are strong enough to accurately shoot at 70. You want all the momentum and kinetic energy you can get.my setup: Bowtech Reign 7, 70lbs comfort setting @ 30.5" draw. Pushing 295 FPS with these arrows.If its something you're interested in trying, PM me as I have a dozen for sale on the cheap.