I will try to do this again to help you with your BP Loading. I am only responsible for what I can say and offer, not for what you understand of that information.
Just to clarify my fatal error was not in what I present to you about my approach to loading but in how you were approaching to get consistancy.
So, now I am attaching a complete BP Cartridge Rifle Reloading Guide from Black Powder Cartridge Rifle forum/website. Please see attached link.
https://www.bpcr.net/site_docs-results_schedules/documents/bp_cartridge_reloading_dick_trenk.htmNow for some noticeable statement to take note of:
1.
"Load the same amount of Pyrodex powder height into your case as you would for black powder. DO NOT load Pyrodex using equal scale weight of black powder. Use ONLY the RS or Ctg. grade not the P grade of Pyrodex in BP rifle cases." THIS corresponds to my comments about different brands not have the same specific gravity and therefore equal weights of different powders will occupy different volumes.
(YES - you can use a scale when your 'final' volume load has been determine but not until.')
(Using only 'volume measurements of different powders", will be the only way to maintain consistent case and bullet loading.)
2.
"WHAT POWDER GRAIN SIZE TO USE
Powder grain size Caliber of rifle cartridge
Fg 45 and 50 cal.(best with case lengths 2. 6" and longer)
FFg 38 to 45 cal. (all case lengths)
FFFg Under 38 cal. (all case lengths)
FFFFg Flintlock primer"Recommendation is to use only FFg in your 40 caliber.
3.
"With a few exceptions, the original black powder era cartridge cases were designed to be fully filled with the appropriate black powder and partial filling was rarely permitted! If BP is fired in a partially filled case having a large amount of air space there may be a danger of producing a dangerous pressure spike which can "ring" the chamber or bulge the barrel. A small amount of air space not exceeding about 1/16 inch seems to be harmless but there is no good reason to have any air space at all and in fact a slight amount of powder compression is always recommended to hold the powder column in a rigid manner and promote consistent ignition pressures."This is my concern over your indication of a 40grain and 50grain loading. That I do not understand how you achieved in a 55 to 57grain casing. I did go back and checked my 45/60 casing will hold 57 grains by volume of tapped FFg Geox. That 57gr volume measurement weighs and average of 51.5grains.
4.
"There are at least three methods of load development which can bring you to a point where you have the most accurate loading for your rifle with a particular bullet.
The first method (along with general assembly steps and suggestions) will be described next.
Many black powder shooters weigh every charge but what appears to be more important is to have the same powder "height" or "volume" of SETTLED POWDER in the case prior powder compression and bullet seating. This is more critical with Fg grain size than with FFg and FFFg grain sizes.Because your bullet may have many seating positions possible, the actual powder height cannot be specified but the following will explain what is required and for these reasons it is usually a waste of time asking other shooters for their "pet" loads. Their bullet, seating depth, powder lot, compression, wad type, lubricants and many other factors will NOT be the same which your gun will be using. Therefore trying to obtain the good results someone else obtained with a certain powder charge and bullet generally does not work too well."What I was trying to relate to you 'before' was 'talking about weighed charges' before you even have every correct component (bullet). In my experience a true 'rifle bullet' will have a larger base to crimp length compared to a pistol bullet. No load you produce with the incorrect bullet will be the usable when you get the correct rifle bullet.
5.
"NOTE: once you have determined the best powder "volume" you can then use a powder measure such as the Lyman #55 or other hopper type dispenser to duplicate that charge volume and speed up your reloading operations. Remember that even with a drop tube attached to this type of powder dispenser, your charge in the case is considered to be not compressed."Yes then and only then will using a scale be acceptable for you. But the relating of the measurement to people like us - is as I said before is USELESS.
My biggest problem with trying to help you - with what you have presented - is how you can get a 1/4" compression on both a 50 grain and 40 grain load in the same casing, because the volume filled are totally different. That was where I was trying to get you to provide more info to fully understand your overall approach. Did you use a filler? a wad? something to get the space filled between powder and bullet base?
Anyway enjoy the full read and maybe this will help you understand loading blackpowder. And why I emphasize the - Volume Volume Volume to correct bullet measurements.
PS: I do cartridge pistol; cartridge lever rifle; cartridge single shot - Grease and Paper Patch; shotgun casing; and percussion pistol and rifle. I seen and done enough to understand right from wrong and what is the normal acceptable approach by others. 'Fatal error' was not a content mistake.....