The 4895 is probably going to be your best bet out of a 1:12 24" pipe imho ... but I'm wondering if even it will be enough. Maybe then8208. With only a 70 grains projectile ... it is definitely not out of the realm of possibilities for any of those propellants at your disposal, in the 1:9, but getting the velocity up to stabilize it through its paces ... only one way to find out.
If I had to place a bet I'd say you might make it to 100 yards, 150 maybe, but I kinda doubt you'll be able to keep it in a tight spiral past that out of the 1:12 24". That would be one beautiful varmint rifle for a 40-55 grain pill though.
With regard to the 1:9 Delton.
I wanna say it was Speer, or maybe Sierra, who published in one of their older manuals that it is impossible to stabilize anything over 67 grains in anything less than 1:8. There was a saying in Aberdeen ... I just can't remember how it went. Somethung like it ain't great unless it's 8 and 68, or 68 in 8 ... or something like that. That was back in the 80s. I'd be shocked if you get really good rotation from the 70 out of the 1:9. I tried some Match Hornady 68s and some match custom comp Norma 69s out of an older M4 Bushmaster 1:9 back when I was trying to work-up a heavier load for that carbine ... I never could get them to work worth a darn out past 150 yards. Fliers all over the place. But out of all of my 1:7 guns, even the 11.5" gun, 1:7 seems to be the magic charm.
Always made me wonder if 1:6 and 1:5 might put a nice spiral on the 85+ stuff.
Both of your barrels will shoot those projectiles ... IMHO I doubt either will do it very well.
