Parker guys,
I wrote this as a response on Doublegunshop.com BBS. I know all us Parkerphiles know this but in case there is one person who is wondering...
Wth equal weights the pressure in the chamber is likely to increase when one substitutes non-toxic for lead. The reason is that non-toxics have different material properties than does lead. Simply put, ITX is harder than lead and does not compress as much during firing. The primer explodes, powder burns forming an expanding gas. The expanding gas creates an increasing amount of pressure which pushes the wad and shot against the crimp. The resistance of the crimp to opening contributes to the pressure. The piston in the wad mitigates some of the pressure as does the characteristic of the shot to compress a little bit.
Nice Shot lists on their web site to add 1500 PSI to your max pressure calculation. I suspect ITX will be similar if not more. The total additional pressure would of course vary due to weight of shot, wad's ability to mitigate the force of the pressure, bore size, and other factors unknown to anyone not having the gear and time to test for pressure change from changes to components, crimps, and other variables.
Note: A roll crimp lessens pressure as compared to a folded crimp.
So, if all would ask Ballistic Products Inc. to develop low pressure loading data for us shooters of vintage SxS's perhaps they will.
Thanks!
Mark
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