Not exactly sure how to word this, but it seems to me it should be possible to come up with a list of target velocities for each barrel length and OBT nodes. Is there any published data?

(Now that i think of it, I guess it gets a lot more complicated because of the almost infinite choice of powders and bullets)

But I'd be interested to know what velocities I should target for this powder bullet combo:

Vanguard 223
24" barrel
1/12 twist
55gr sierra gameking
Winchester brass
IMR 8208 powder

Is that barrel length the actual barrel length measured from the bolt face to the crown or is it the manufacturers published spec?

It's the manufacturer's published spec. I do believe it does measure 24" from the bolt face to crown.

The OBT method recommends measuring it for better accuracy in determining nodes.

There isn't a simple relationship between velocity at the muzzle and OBT because different powders will accelerate the same bullet in different ways.

Think about drag racing. Two cars could have the same elapsed time but different trap speeds, or they could have the same trap speeds but different elapsed times.

Sorry, I was going to run this for you but I realized that I don't have a recent data update that includes IMR 8208 XBR.

In order to give you the best results possible you'd also want to provide more data anyway.

Cartridge over all length?
Bullet touching/jammed into lands at C.O.A.L. (Y/N)?
Measured bullet length?
Case water capacity (measured level to case mouth)?
Barrel length (measured bolt face to crown)?

The more accurate the data you put in, the more accurate the data you get out (also known as "Garbage in = Garbage out").

The node (or what I consider the vibration of the barrel due to the bullet passing down the barrel) would be based on the diameter of the steel and change through its length, the wall thickness of the steel and change through its length, the steel alloy, the heat treating of the steel, and probably many other factors.

Original Optimal Barrel Time Paper

http://www.the-long-family.com/optimal%20barrel%20time.htm

This has the list and two versions of the calculator. The excel one didn't work for me but the non excel version did.

This version is based on barrel time only so it is just one parameter. But somehow it can be an accurate prediction. Even better when used through Quick Load to determine which powders and charge weights get you there within pressure limits. I think this assumes a completely free floated barrel and it is still subject to field testing. It is just a mathematical prediction to get you approximately in the ball park.

Based on a 24-inch barrel, I believe you're looking for a velocity of about 3185 fps. What QL is saying is that you'd be getting about a 95% burn. My feeling is (and I could be wrong) that velocities might not be be consistent enough to take advantage of OBT. Who knows, though? It could work like a charm. It's worth a try.