What velocity increase per inch?

[jimbob86]

Powder type and amount does make a difference. And as most rifles with all sorts of barrel lengths show flames coming out of the muzzle if observed in total darkness, that's usually considered proof that there's still powder burning outside the barrel. And with some loads of some powders, unburnt granules can be seen on the ground in front of the muzzle

+1

By choosing a faster powder than the ones at the top of the list for my 16" barrelled Ruger Frontier, I get a whole lot less flash and blast out of the muzzle, less recoil, and don't lose nearly as much velocity as one would think out a barrel 8" shorter than what the load data was developed in ....

 

[surveyor]

Same load, almost same jump to lands(within 0.006)
20" barrel semi auto
2683,2689,2688,2668,2706

30" barrel bolt action
2835,2828,2840,2835,2803

This is a 0.100 jump to lands and mag length

Velocities were higher at .020 jump, but I don't have a direct comparison.

I mainly went looking for a load for the 20" first, as close as the chambers were I thought it would give a little insight working a load for the 30"..

Not sure what the overall takeaway as far as barrel length vs velocity would be, as
They are diffrent rifles, actions and other factors involved.

These were 223..