Loading to Optimum Barrel Time (OBT)

The name suggests a Optimum Charge Weight (OCW) test to me. Where you test to find the charge range with the most consistent point of impact, idea being the bullets all leave the muzzle at the same point in the barrel's harmonic oscillations.
 
My understanding is the results are much like a ladder test, in that it will narrow-down the loads that are more likely to give best accuracy in a given gun/barrel.

Frankly, that is about the limit of my understanding. I'd like to know more. I'm going to start loading for my .338 this spring and I'd like a shortcut that would save me a little money.
 
I have used OBT, or Optimal Barrel Time for loading. The website is at: http://www.the-long-family.com/optimal barrel time.htm

The theory is that all barrels, dependant on length, have an optimum travel time through the barrel, of which, there are multiple nodes for each barrel. There is a pdf on that website highlighting the barrel times for each barrel length. To complete this, you need to have Quickload, and a good chronograph.

1) Setup load in Quickload, input all parameters, including powder, etc, etc. Use a combination which will get you the lowest barrel time (ie the fastest) but not going over the SAMMI spec for pressure. Load say, 3 rounds, and shoot them through a chronograph.
2) Measure the water volume of the 3 cases. Use the average, and tweak the empty case volume parameter in Quickload to match. Alter the BA (burn rate of the powder) to get quickload to give you the OBT you were aiming for in Step 1. This should be darn near on the money.

Using this charge weight, load 3 rounds at varying OAL's (3 rounds per OAL), and evaluate. The above is a coles notes version of what I have done, only a bit more extensively. Before trying, read the actual website, there is an article on tuning quickload.

I have done OBT and OCW alongside one another, and they align.

AS ALWAYS, WORK UP!
 
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