You must have missed the part of my recent post where I've done a lot of testing of "guessing" pressure with a chronograph by comparing the results to SAAMI loading data. Yes, you can come very close to estimating pressures with chronograph results. I've done it dozens of times.
In fact when the .300 WSM was so new there wasn't any SAAMI reloading data, a magazine assigned me to work up some loads, in order to beat the competition with the first .300 loading data around.
I compared the powder capacity of the .300 WSM with the .300 Winchester Magnum, using water and a bullet seated to the same depth in fired cases. Using a simple internall ballistics formula, I figured the .300 WSM should get 98% of the velocity of the .300 Winchester Magnum, so worked up some loads with popular .300 Winchester Magnum powders using that guideline.
My loads were published in HANDLOADER magazine, and when pressure-tested data came out over the neat year, only two of my 10 or so loads varied an entire grain from the pressure-tested data--and one of those was a grain under. The others we either spot-on or within a half-grain. And that's just ONE example among many of using a chronograph to estimate pressures.
As another experiment, I once loaded for the .270 using all the the traditional pressure signs, including measuring case-head diameter, to what were apparently "safe" levels. I then took of the same ammo to a piezo lab, where it tested almost 68, 000 psi.
Now, I did ignore velocity as an indicator in that test--and it turned out that the velocity I was getting was faster than any published data, and the powder charge also higher than any listed for that bullet weight.
Yes, there are ways of guessing pressures that are more accurate than bolt-lift and primer pocket tightness.
This is great. So what is your best velocity "guess" in a 24" barrel for the 175 partition say in a long throated 7mm Mashburn Super Short magnum?
