another doubter here. Alliant lists 68 grains with a 140 going just over 3100. One grain of powder sure isnt giving you 400 fps and for the most part if i looking at the data i have for the 300wsm aliants velocity readings are a bit optimistic as it is. If your chronograph is a ohler and you have it at least 15 feet away from yur muzzle id believe it. But if your chrono is to close you may be getting readings from your muzzle flash or if its a chrony or some other cheap chronograph id be doubting my readings all the time. Ive had two chronys both went back because they read about 200 fps higher then they should of compared to my buddys ohler. Even after paying to have them fixed they did the same. they were given away and replaced by a pact. Not an ohler but a pretty good unit non the less. Bottom line is my 7stw has all it can do to get to 3500 with a 140 and your just not going to do it in a wsm without leaving parts all over the range.
Ive never been a fan of the short mags. Ive loaded for my buddy enough to know they are good rounds if you use them for what they are. His 300 will out pace an o6 but wont run with my 300 win and surely not with my 300 wby or 300 ultra. I did the other day finally get over my mental block on them and buy one. I found a abolt hunter in the gun shop for a good price in 300 wsm. It is a light little 22 inch gun. Figure it would be a great gun if a guy needed mag power but had to tote it up and down the hills all day. I sure dont expect it to run with my 300 ultra though.
Has to be an Olher? I use a Pact Mk IV and don't believe it's ever let me down. I'm not so impressed with how fast a bullet can be driven anymore. A proper cup and core bullet in any magnum I can think of will do all most people want. I am wondering what your gonna shoot with a 139gr SST at that velocity that bullet preformence is guaranteed? When I shot magnums my favorite was the 7mm Rem Mag. I had the throat let out quite a bit to be able to seat the bullet out farther. My bullet of choice was the 160gr Speer Hot Core. I used 69.0 grs of N-205, two grains over max. No pressure signs and no chronograph's around back then so the bullet could be going as fast or slow As I said. My Speer manual back then had 67grs going something like 2800-2900fps. But the real beauty of the 7 mag that I believe now, is the ability to handle heavy bullet's. That gets pretty much thrown out the window with the new solid TSX type bullet's. If you really are getting that kind of velocity with the 139gr SST bullet, it would be interesting to see what would happen with the bullet hitting at 100yds or less. Might leave a crater and blow through a deer and may just come apart on an elk, wounding it. The advantage to TSX type bullet's is the ability to maintain weight. penetration is a product of weight and velocity. Unfortunately, a cup and core bullet driven fast enough to break up on game will normally shed to much weight to penetrate well.
Recall a number of years ago on here the fuss about the Nosler BT blowing up on animals? Caused by to much velocity for the bullet to handle. To many, not all, would hit the side of an animal and blow a horrible wound with very little penetration. That is a product of a bullet being to light to function at the velocity it was running.
Were it me using that 7mm wsm, I'd leave the 139gr bullat for a lot heavier bullet or if you feel the need for speed, go to a TSX typr bullet that light.
