I've been wanting to load some 150's for my Browning Bar lightweight with a 20" bbl.
I coronographed some WWpp's in my rifle at 2800 used the same in a 22" Bar for 2870. factory says 2910 in their lit. with a 24" bbl.
I would like to get a little more out of my 20" bbl with good accuracy, also something that will function in my auto-loaderand not tear itup.Sometimes I have to take a 300 yd shot, and I don't like holdovers, I just want to hold on target and squeeze.
Are there any safe loads loads that will work in my Bar ?I tried 52 grains of 4064 and couldn't even break 2800. I might mention that this Bar is an unbelievable shooter 3 shots thouching ar 100 yds with just about anything you put in it.
I might be sighting it in wrong, 2" high at a hundred haven't missed a deer yet with it but I didn't feel comfortable shooting one at near 300. Yet I got the deer(no tracking)
I've been toying with the idea of trading it for a 22" bbl .270 but it shoots so darn good ! and I don't know what I will get.

Sierra list loads with 150 grain bullets @ 3000fps, 52.8grs of 4064 being one. But that's out of a 26" test barrel. Deduct the generaly accepted approximate velocity loss of 50fps per inch of barrel loss (6" x 50fps = 300fps) and you wind up with a MV of 2700fps. The 52.8 grain load Sierra lists is a max load. The other loads they show giving 3000fps with 150gr bullets are also max loads. Load, and shoot over a chrono is the only way you're gonna' find out.

You actually have what I would consider a "faster than normal" 20" bar. You might squeeze another 50-100 fps out of it but would probably be approaching "hot" loads. I'd have to run it on my ballistic program but another 100 fps might give you another 1.5" (maybe not even) of "flatness".
If you have a great shooter what you really need to do is practice those longer shots. I wouldn't think in the real world with a 2" high at 100 you'd have to aim over a deers back at 300yds. Another possibility would be to get one of the new scopes that has the dots or hashmarks for longer range shooting. If you have that accurate of gun--don't waste time "searching" for speed--spend time knowing your ranges and practice, practice practice.