Re: On the right track but need some help still.
I would look at the crown first. You can do that with a magnifying glass and some good light. Sunlight works great. At the muzzle where the flat part of the barrel and the rifling meet there should be a smooth, consistent angled junction. It's usually at an 11 degree angle and should be free of burrs and rough, chatter machine marks. When you shoot several rounds you should be able to see where the powder leaves about 5 or 6 consistent "marks" on the end of the barrel. These are meer powder smudges and wipe off with your finger but give you a good indication if the gases are leaving the barrel consistently and evenly behind the bullet. If this is messed up you'll play hades trying to find an accurate load.
If your heart is set on the 140gn, I would try a faster burning powder, after checking the crown. I first tried the 180gn Ballistic Tip in my .300 WinMag with RL22 as Nosler #6 said that was the most accurate powder tested. Accuracy ran 1.0-1.5" at 100yds. I was dumb founded. My first 7Mag loved RL22, why didn't this rifle? I tried H4350 and walah! Accuracy ran in the .3's. I then ran the 180gn MatchKing with RL22 and accuracy ran in the .3's. I can't explain this, I just feed it what it likes.
I would get around to trying other bullet weights also. I recently brought my boss's 280 Rem home to zero it in with Hornady 139gn LM factory ammo he had. I cleaned the barrel thoroughly and was amazed when it sprayed bullets in a 6-8" "pattern". I tried several 3 shot groups and the results were the same. I resized that brass and prepped it like I do all mine and loaded some 140gn Ballistic Tips and accuracy ran pretty much the same as the factory fodder. I then tried some 120gn Ballistic Tips ahead of XMR3100 and what a difference. Accuracy went well under an inch for this bullet and the Sierra 120gn Spitzer. I guess this barrel's twist is not compatible with the 140gn range of bullets that I tried. I haven't tried anything heavier than 140.
It may take a little experimenting and can be frustrating at times but be patient and hopefully you will find that "holy grail" load. Keep us posted with your findings. JohnnyK.
Last edited by johnnyk; 09-30-2009 at 09:55 PM.