Took the GBL out today for some range play at 100 and 350 yards.

Load was:
Rimrock 405gr cast
16 gr Unique
CCI 200
R-P brass

Load clocked right at 1300 fps (1280-1300 fps at 15').

At 100 yards I put six rounds downrange from prone with a front rest. Five went into a 4.5" group, and one keyholed about 3" further out at 7-oclock.

I figured stability must be marginal with the keyhole, but went out to 350 yards anyway, on the 15x25" steel. Cranked 30 moa on the scope, and the first round was a (lucky) hit. I fired five more and they were all over the place, off steel. Literally had a 'beaten zone' probably six feet in diameter. They must have all been tumbling.

Had another 38 rounds to expend and did so just fooling around plinking at rocks and stuff.

So, looks like I need to speed up these 405s some to get stability. Barrel twist is 1/20". Anybody have insights regarding minimum velocity to get good stabilization with 405 cast out of a 1/20 bbl? Or does this seem like an issue with the bullet?

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