NitroX, you have received much good info in this thread. I will add my experience for what it's worth. Bought a terrific 1903 several years ago and scrounged up a small amount of brass to use in working up loads. I normally do not use factory ammo for any reason except to make empty cases. But when I stumbled across a stack of 6.5 M-S ammo in the old wood grained boxes at a Birmingham gun show, I jumped on them. There was 11 boxes of 139 gr spire pts and a single box of 156 RNs.

The spire points had to be slammed hard to get them to feed. The RNs fed OK but I only shot one. The velocity of it was about 200 fps more than the 139s, so I pulled the rest down and loaded less powder. Had a lot of fun shooting all those loads but the hard feeding was a PITA. Actually killed a 6 pt whitetail with a 139 before they were all gone.

I tried 129, 140, and 120 gr SPs and none would feed smoothly. I eventually settled on Hornady 160 gr RNs and PPU 156 kinda sorta RNs. They both feed very well but require an exact OAL to do so. They work on WTs very well but I would use SPs if I could get them to feed slickly. Many people have had luck with SPs but not me.

Hope yours is easier to feed than mine!