Got time to cast a few bullets for the Mustang rifle today..
where do you think I should start at? I will be using Goex 2F
of course..Hope it is nice out tomorrow..

Start at 70 grains and work it from there... they look REAL nice..

I tried a few in my 21" GM 1:28 barrel today using 80 gr ffg T-7 and they looked promising. I'm switching to fffg Goex next trip out, though. Just a little hesitation on ignition with the T-7 and I was using musket caps. Back to real BP & #11s for me I think.
I usually start off around 70 - 80 gr with a .50 cal.
So far everything I've tried the 250 gr REAL in has been acceptable on accuracy. The 1:48 T/C NewEnglander really likes them, the 1:28 GM barrel seems to like them, and the 1:28 inlines weren't great on accuracy, but it would be plenty good enough for a quick load for a follow-up shot if needed. Even the Lyman Plains Pistol seem to shoot them well.

Hey Johnny2, I checked my Mustang records and can give you some poop on my experience with Lee 250 grain REALs. I shot some last May over a chronograph, usingPyrodex RS and a 1/8" Circle Fly fiber wad under the bullets.

(All groups were five shotsat 50 yards.)

70 grains powder - 1281 fps average - four shots into 1 & 7/8"- one flyer expanded group to 3 & 7/8"
80 grains powder - 1375 fps average - four shots into 1 & 1/2" - one flyer expanded group to 2 & 7/8"
90 grains powder - 1420 fps average - four shots into 1 & 3/8" - one flyer expanded group to 3 & 1/8"
100 grains powder - 1510 fps average - four shots into 2 & 1/4" - one flyer expanded group to 2 & 7/8"
110 grains powder - 1581 fps average - five shots into 2 & 3/4"

DANG those flyers! Sometimes it was the first shot, sometimes the second, third, fourth, or fifth. (It couldn't possibly have been my shooting! ) Good shooting records are nice to have.

And what does the circle fly wad do......????????????

Better gas seal, and protects the base of the lead bullet from flame cutting. In my experience, a wad under the REAL decreases group size.