Thread: What causes key holing in sub loads

Originally Posted by Marty Henry

Two gas checks? Measure the length of one and whack it in this formula 150 x the bullets diameter in inches squared divided by the bullets length. The answer is the twist rate
eg bullets diameter is .308, length is 1.5 inch
150x.095/1.5 = 9.5 the twist needed is 1:9.5
My 185 grainers measure 1 inch, I run them at 1450 fps with no gas checks but a good lube.
Maca has raised a good point even with a gas check if you try and push them too fast they will strip, tumble and give you a big cleaning job. A lack of lubricant will also do you in.

My sub guns action is Stained with the lube that comes with the projectiles so I think there is plenty of lube
The bullets measure 0.984inches
Am I right to think a gas check is a recessed ring at the base of the projectile filled with lube? As there's two of those and one more above that's not lubed

If I replace 1.5 inches with .984 it gives me 144 which I imagine is 14.4 inch twist
One gun is 1/10 and the other is 1/11 both seem to keyhole around a third of shots
I'm not having this issue with 165gr ballistic tips at around 1050fps
The only lead bullet Iv recovered so far was too damaged to tell if it's taking the rifling or pushing past it