For those interested, y’all should read Harold Vaughns book titled “Rifle Accuracy Facts” . Mr Vaughn certainly doesn't have John Barsness writing skill, but there is a lot of good info there. I have read this book several times. Made a lot of the same test. Got a lot of the same results.
One of those test I could never understand, or maybe I couldn’t accept the results. Mr Vaughn was testing muzzle blast, and its consistency . The blast was hardly ever the same. In my mind, thats impossible.
So I did my own test. First, I developed a load in a 308 that had 6 fps extreme spread on a 10 shot group, and less than 200 psi swing on the pressure. It took a lot of brass and bullet sorting to get that ! Next I set up a bench outside in an area about 5 acres that was open and flat, grass mowed evenly. Then In an area about 20 ft diameter, I spread ground up fiberglass insulation, the kind you blow in. Spread about two inches deep. Then fired, made a little drawing of what the fiberglass did. Then waited for it all to settle, then smoothed and added until I had about two inches.
I tested this on four different occasions. Each time I would fire and record ten rounds. I dont think in all that test I ever saw the same effect twice. In my mind, thats impossible. But the test said otherwise.
Charlie
