Pressure in a shotshell

[J.B. Books]

Originally Posted by Frank Srebro

This seems to discount the theory whereby a taller shot column - as with the same weight (mass) of bismuth vs. lead - will result in increased pressure due to more surface/friction of the shot against the bore, as the shot is accelerated. Just sayin.

Where is the evidence of that? Do you believe that surface area of the shot column against the bore has no effect on pressure?

Case in point. Sherman Bell's data for the Short Ten shows a Fed Hull, Win 209 primer, 32gr of SR7625 with SP10 wad and some filler for both 1 1/4 ounce lead and 1 1/4 ounce of Bismuth. The lead load uses a folded crimp and generated 6700 psi. The Bismuth load using a Roll Crimp (which reduces pressure) generated 7100.

I suspect if that Bismuth load had used a folded crimp there would be somewhere around 1000 psi greater with the Bismuth.

[Big Friend Ten (BFT)]

Originally Posted by Pete Lester

Where is the evidence of that? Do you believe that surface area of the shot column against the bore has no effect on pressure?

Pete,

I believe it would have an effect but compared to the other factors, especially with modern plastic wads, that effect would be negligible.

I also believe that all else being equal a slower burning powder will produce less felt recoil than would a faster burning powder. The results of tests of this theory are subjective depending on the individuate test participants.

I like theories but am forced to accept hard data.

Mark

[J.B. Books]

Originally Posted by Mark Ouellette

Pete,

I believe it would have an effect but compared to the other factors, especially with modern plastic wads, that effect would be negligible.

I also believe that all else being equal a slower burning powder will produce less felt recoil than would a faster burning powder. The results of tests of this theory are subjective depending on the individuate test participants.

I like theories but am forced to accept hard data.

Mark

I think I gave a pretty good example of the effect.

[Big Friend Ten (BFT)]

Originally Posted by Pete Lester

I think I gave a pretty good example of the effect.

Pete,

Sorry, but I reread your posts in this thread and did not see it. Please include a link or the information in this thread for consideration.

Mark

[J.B. Books]

Originally Posted by Mark Ouellette

Pete,

Sorry, but I reread your posts in this thread and did not see it. Please include a link or the information in this thread for consideration.

Mark

It is from Sherman Bell, check the last page of the Short Ten spreadsheet I put up this week.

[Bindlestiff]

Originally Posted by Pete Lester

Case in point. Sherman Bell's data for the Short Ten shows a Fed Hull, Win 209 primer, 32gr of SR7625 with SP10 wad and some filler for both 1 1/4 ounce lead and 1 1/4 ounce of Bismuth. The lead load uses a folded crimp and generated 6700 psi. The Bismuth load using a Roll Crimp (which reduces pressure) generated 7100.

When loading shells, the shot is measured by volume and listed in ounces. I suspect the volume/ounce conversion is for lead. Do you think Sherman weighed or measured his Bismuth load? If he measured the shot and given Bismuth is less dense than lead, the Bismuth weight would be lighter than 1 1/4.... but generated higher psi. What would that indicate?

[J.B. Books]

Originally Posted by Robin Lewis

When loading shells, the shot is measured by volume and listed in ounces. I suspect the volume/ounce conversion is for lead. Do you think Sherman weighed or measured his Bismuth load? If he measured the shot and given Bismuth is less dense than lead, the Bismuth weight would be lighter than 1 1/4.... but generated higher psi. What would that indicate?

Since Bismuth loads are stated in weight and not volume I have always used an adjustable bar or a modifed mec bar that throws the desired of weight of Bismuth. I have never heard of anyone doing otherwise.

An equal weight of bismuth to lead is going to have a taller shot column.

PS. I am pretty certain Sherman weighed his Bismuth loads, the evidence is the difference in amount of filler wad needed for the same weight loadings vs. lead.