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Excellent question- I did make a mistake with the granulation - it should have read SINGLE F or 1F.
: 12 guage modern loads are assemmbled to a max of what is called 3 3/4 dram equivalent for 2-3/4"cases and 4 drams for the 3" cases - supposedly giving the same velocity as if it were a BP load - not so. Our GOEX is not equivalent to the powder used in the 19th century, being about 20% inferior. Perhaps Swiss powder would match the drams equivalent, I don't know - it isn't available here.
: Even modern shotshell data(trap or skeet loads) for 3 dram equivalency developes a max of 11,000LUP as does all smokeless factory ammo. With smokless powder, and built-up wad columns, we can develope loads that equal what heavier loads do with black powder.
; My data reveals I misquoted the actual velocities generated by 1F BP.
: With our black powders, it took 5 drams of real BP just to give 1,350fps, and 7 drams to make the reqisite 1,500fps.
: We know from Lyman's data that the 12 bore black powder loads develope much less pressure than the drams equivalent actually shows - and - most larger bored BP rifles develope similar pressure for a given velocity, whether is it a .50 cal., 58 or 73. This means a .50 cal rifle developes 1,500fps at the same pressure as a .58 does at 1,500fps, and even a .62 or .73- all developing the same pressure at the same velocity of 1,500fps. As Lyman's BP data shows roughly 8,000LUP for 1,600fps, we can assume that each calibre developes that same 8,000LUP at that same velocity. It is an equation that seems to conform well, in favour of the larger bore. The larger bores actually develope lower pressure for a given vleocity than do the smaller ones, but the difference ins't much.
: As modern shotguns handle pressure at 11,000LUP to 12,000LUP in normal & heavy loads, we should be able to work up loads in BPowder to equivalent velocities.
: From this, I worked up loads to the 7 dram level given in my original post. As with all handloading, we must develope safe loads from a low starting point.
: The heavy BP load of 7 drams showed no more pressure signs than any 2-3/4" magnum load with 1-1/2oz of shot. I surmise the pressures are equivlent at around 11,000LUP or under.
; For my smokeless loads, I used Lyman data which shows velocities up to 1,500fps at 10,000LUP with their hollow-based 445gr. slug using 32.5gr. SR7625.- With a Federal primer, they loaded up to 35gr. 7625 for an additional 15fps for an added 50LUP. The same 32.5gr. data gave me 1,500fps with the .684" round ball.
: Using 48.5gr. BlueDot, they got 1,525fps with the 575gr. solid Vitt-Aerodynamic slug. From that data, I decided I could increase the BlueDot loads slightly, to 50.0gr.when using the lighter round balls. This load was safe in my old double, so should also work just fine in any modern shotgun. It put me up to 1,650fps using the lighter round ball. As the slugs they used develope higher pressure than a round ball, due to friction from their length, I surmised these loads could be matched or equalled with real BP, which developes even less pressure than the smokeless ones. This proved out in fact as I worked up to the heavy load listed. It took 7 drams of modern real BP to match what I received in smokeless loads. Note I did not use T-7 or Pyrodex- only 1F GOEX black powder.
: 545gr. RB at 1,500fps is very possible from the double or pump gun as Lyman lists the Bluedot load at only 8,920LUP. With proper load development, this can be improved upon. Only slight improvement is necessary to bring it up to an actual 7 dram equivalency. My buddies used the 7625 loads for their RB loads to cary when out duck hunting. More than one of them have shot their moose with these while sitting in a duck blind, pelting ducks.
: I used WW or CCI209 pirmers for all loads.
: I guess the standard warning should have been applied. The noted loads were safe in my shotgun after careful development, they may not be in yours.
; I shoudl note that old ammo with 'Pumpin Balls" weren't accurate. This is due to the wad column and small size of the ball used. This is why I suggested using .715 balls in open-bored guns, and the .684" or perhaps .690" in choked guns. Full choke is .690" which is 40 points of choke. The ball should pass freely thorugh the choke, and is held in the centre of the bore by the cup-wads taken from modern plastic shot-cups. As well, there should be a Card Wad between the plastic and the BP loads as Bp will melt and coat the bore with plastic.
In reply to:
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earlier quote - I used data for 1 1/4 oz. and 1 3/8oz shot (with) SR4756 and SR7625 (to) easily get 1,500fps

: I was mistaken about the shot-load data- it should have read for their slug data, not 1-3/8 or 1-1/2oz. as the shot loads developed sub-standard pressure and velocties. the slug-data uses more powder as slugs (or round balls for that matter) developed less pressure than do shot columns.

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Daryl

"a gun without hammers is like a Spaniel without ears" King George V