10 gauge loading question
 

I am currently loading 1 1/4 oz Nice Shot 10 ga. loads in both Remington and Federal cases using Sherman Bells loads for 1 1/4 oz. Bismuth in these cases. According to his info they develop 5900 and 5800 psi respectively with roll crimps. My questions are what would happen to pressures if I used the 6 point crimp instead of the roll crimp and is there a difference in pressure between Nice Shot and Bismuth? Also what is pressure difference between lead, Bismuth and Nice Shot? Thanks for your input.

I am all for experimenting within reason but there is no comparing Nice Shot to Bismuth and by substituting Nice Shot for Bismuth in a published Bismuth load means you have no idea what the pressure is. There is only one published load for Nice Shot in the Short Ten and it is a 1 3/8 ounce load. Nice Shot can be substituted for lead in any published load but you must add 1500 psi to that load when using Nice Shot. Bismuth being lighter requires a taller shot column than an equal weight of lead. That means more surface area against the bore and more pressure. I would not feel good substituting Nice Shot for Bismuth but I would be fine using it in a lead load with low pressures. From what I understand all things being equal a roll crimp reduces pressure 600-800 psi over a folded crimp all else being equal.

pete i thought a roll crimp had less pressure than a 6 point or 8 point crimp..charlie

Follow the lead recipe for 1 1/4 oz and take account with additional PSI increase like Pete said. I would not shoot the loads you have that have bismuth since the pressures are unknown.

I have used Long Shot with 1 3/8 oz of Nice Shot #2 for ducks and geese and I believe Pete has it in his 10 gauge spreadsheet. I put a 16 ga. felt wad in the shot cup under the shot for better crimps for this load. Devastating load to feather'ed critters....

http://www.randywakeman.com/Nice_Sho...a_10_Gauge.htm

The only way you are going to know for sure is to carefully load at least 3 shells preferably 5 and send them to Tom Armbrust for pressure testing.

I understand that bismuth would have more surface area against the bore as compared with lead (with the same weight/diameter of shot), but why would that result in more pressure? Can you please elaborate? Thank you.

I too thought a roll crimp had less pressure than a fold crimp. The depth of a crimp effects pressure whether a fold or roll, so maybe a deep roll crimp would have more pressure than a normal fold crimp. If you're loading at low pressure with normal depth crimps I don't believe it makes much difference which crimp you choose. JMHO

Charlie and Paul, what part of my last sentence is/was not clear?

"From what I understand all things being equal a roll crimp reduces pressure 600-800 psi over a folded crimp all else being equal."

i reread this thing 4 times..i dont know where i got this in my head that you said roll crimp was more pressure than 6 point or 8 point crimp..pete plainly states 600 to 800 lbs less pressure with roll crimp...my mistake...charlie

Frank, chamber pressure is created by the resistance of the ejecta against being moved forward. Resistance is either + or - by changes in the weight of the ejecta and by changes in the amount of resistance/friction of the ejecta against the barrel wall. An equal weight of Bismuth, say 1 1/4 ounce has a much longer shot column compared to 1 1/4 ounce of lead. (1 1/4 ounce of Bismuth has a little more surface area against the bore than a 1 3/8 of lead.) The larger surface area of the shot column creates more resistance through friction and increases pressure. That is why Bismuth can not be loaded using lead recipes for the same weight with an expectation of similar pressures.