Quote:
Originally Posted by Mark Garrett
Ron , Certainly didn't mean to offend you . Just want everybody to stay safe. But I will stick to what I said , a taller or "longer" load column will increase pressure every time , more surface area friction in the hull .
Hope you and yours have a Happy Thanksgiving also.
Mark
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Mark, I am sure your intentions are good -- but you are incorrect and spreading misinformation when you state that a longer load column (in and by itself) "will increase pressure every time." That statement is simply not true and can easily be refuted by this simple example: Take a known safe 12 gauge load with 1 1/8 oz of shot. Measure the length of the load column -- lets say it's 1" (for example, I didn't measure it). Some of the space in the hull is taken up by the plastic wad. Replace that plastic wad with a thin over powder wad and fill up the rest of the hull with a light weight material, like rice. That rice will be much lighter than the lead and the "load column" (the rice) will be much longer (maybe 2x longer) because you replaced the length of plastic wad with rice.
I guarantee you with 100% certainty that the longer yet lighter load column of rice will produce significantly less pressure than the shorter, heavier load column of lead.
It's the weight of the load column and to a lesser extent the compressibility of the payload that determines the pressure of a given powder charge. It has virtually nothing to do with the length of the payload. That's why Victor's comments are spot on:
"I tested the same load twice: one test with 1.25 oz of bismuth and one test with 1.25 oz of lead. All else the same. I was not surprised when the velocity and pressure data were essentially the same for both loads.
What’s heavier? 1.25 oz of bismuth or 1.25 oz lead?"