Hey tobehunted, the 6.5 rem mag is a great rebarrel caliber for a win mag caliber. Mine was a Browning 300 win mag with a detachable magazine that had a huge jump to the lands. When I decided to rebarrel, I got some 6.5 rem mag cases and dies and loaded a dummy unprimed cartridge and sent it to the gunsmith and told him to set the freebore to fit
the COAL was 3.10" IIRC. Those 6.5 bullets are looong! That is a 130 gr Accubond in the pics.
If you want to shoot the 140 gr bullets then I would recommend a 1 in 8 twist although a 1 in 9 would probably do fine. I had a friend who had a 300 win mag and he like my 6.5 so I had his rebarreled with a 1 in 9 Shilen barrel and it shoots 130's well.
Mine is a Douglas XX #4 contour finished at 26". I did a seating depth test shoot today