Originally Posted by eshell
Hey Steve, FWIW, my 6.5-300 Wby used 83.0 H-870 to drive a 140 SMK to 3,400 and into 1/4 moa groups. The same charge sent a 120 Nosler BT at 3,500 and also into 1/4 moa. Sid Goodling built and refreshed it for me.
After setback, I quit using H-870 due to the fouling. I also lost almost 3" total barrel length, between 2" at the chamber end and a re-crown.
I found IMR7828 way too fast and am currently using 74.0 Retumbo to drive a 123 Scenar at 3,400, which also yields 1/4 to 3/8 moa accuracy. I had decided to quit making it sore just playing with it and stopped working on new loads there.
Ahh.... The good old standby load of 83gr of H870. Shot a few of those loads myself at right around 3400fps also. Honestly the luck we had with IMR7828 was based on powder purchased back in the late '80 early '90s after it first appeared on the market. I still have some of that powder left. I haven't tried any new 7828, so maybe it has changed burnrate enough to make it too fast. That could very well be the case.
I used VV N170 to get 3512fps avg out of a 5 shot string using moly'd 140 SMKs. But like I said it stretched the brass out in a hurry and didn't shoot for @#$% anyway.
I guess I need to dust off the old girl and try some of the modern slow powders in it. But it needs a new barrel first. It's slightly "used". ;)
I guess I should simply rechamber my 6.5-300 Win Mag out to the 6.5-300 WWH. That has a 34" barrel. So after cutting off some threads and rechambering and recrowning I should still be around 30"+ mark.
Good luck Hank. If that has a throat for the 155s you should just barely get a 140gr SMK to seat into the neck of a case when touching the lands. My 6.5-300 Win Mag is throated for 155s and I have the same issue. My 6.5-300 WWH was throated for the 140s though.