RE 25 has a SLOWER burn rate than does RE 22. IMR 4350 or H4350 is a little too fast for a 270 WBM. RL 22 with 73.5-74 gr with 130 gr Barnes X and TSX nets 3360 and 3400 fps respectively. I played with some IMR 7828ssc with some 150s in the same Mark V WB rifle with no such luck. Groups were in the 1.5-2.5" range. The 130 TSXs shot the best slightly beating out the plain 130 X with groups in the .3s and .4s. If you want to shoot heavier bullets than 130s, a general rule is to slow the burn rate as you increase the bullet weight. Just something to keep in mind. Best of luck!
On the duplicating factory 270 Weatherby note. A good friend of mine wanted me to match the 150 grn Wea load in his Mark V. I achieved this w/ 71.5 grns R22 under the Hdy 150Grn SPILFBs (Same as Weatherby Spire Point loads)Weatherby brass and Federal GMM 215s were used. I roll crimped into the cann.
That load chronoed 3265 at 10-12' and shot less than an inch at 200. It is dynomite on whitetails.
I achieved the same velocity w/ IMR7828 but accuracy wasn't nearly as good(around MOA).