Good info Gus.
I have the Long Land Patterns by Kit Ravensheer. The 1740 musket did have a slightly lower comb and drop. I think there were a few reasons for that design. One the forestock was beefed up because the steel rammer allowed for a smaller diameter rod hole, so it would increase the wood between the rod channel and the forestock, this of course required a new cut pattern, so lifting the butt stock to a higher profile deliberalty gave the ordance more stocks from a single perceive of heartwood walnut. Having held both patterns, you really don’t get the feel that the 1756 is harder to shoot than the 1740 with a single round, HOWEVER the 1756 does have at least 1.5 extra lbs of weight on it because the stock was overal larger, and the lock was slightly bigger too, the casted pipes were thicker and the steel rod added more weight. The 1740 musket has a lot of wood, but the larger diameter wooden rod makes the musket much more of a Fowler like feel, with a weight of around 9 - 9.5 lbs, the 1740 is a nice musket to shoot with decent balance. One other thing about the 1740 pattern that shifted to the 1756 pattern was the ‘transitional’ Brown Bess long land of 1746/1748. Some ordance contractors were making the 1740 with a steel rammer, they simply did this by taking a 1740 pattern stock and drilling a smaller rodhole, later pattterns were also designed with a more customized stock pattern, with the butt stock shape my best prerogative is that these were very expensive to make with the 1740 lock and stock. The 1756 was just more cost effective, everything was straightened, the lock, the stock etc. The 1756 Long Land is very much a beast of musket, I once saw an auction for a Coach Harness / Kit Ravensheer 1756 Bess, this used the 1762 Pedersoli Grace Lock, an absolutly stunning musket.
The American Springfields I find are more direct copies of the French Locks. The barrels and stocks are similar but smaller in size. The only thing that puzzled me was the 1816’s total lack of a comb I would think that would make the gun easier to aim but raising the butt higher would force the muzzle down, so I never understood the profile of the 1816, in fact I see the 1835 and 1840 muskets as a perfection of the 1816, they dropped the butt a little and raised the comb, allowing for a more straight shot. The French on the other hand kept the larger butt stock with the cheek recess profile.
Nick