Current loading manuals are not of much use for the old cartridges.
I believe the original .44 Colt was for the Colt Army revolvers based on the 1860 configuration, so had a very small rim and a heeled bullet that I see listed as .430" heel, .451 full diameter. That makes sense as the bore diameter was quite a bit more than .44 in the cap and ball guns. In that vein, we convert the modern black powder revolvers directly to .45 Colt, but only as 5 shooters or with precisely offset bored chambers to make 6 rims fit.
There is ammo out there now days that is called .44 Colt, but it uses an inside lubed bullet of smaller diameter ( ~.430") and a larger rim than original (doubt 6 would fit in a straight bored cylinder), and I expect dimensions found in most references could easily be a mix of old and new.
Just to further the confusion:
Cartridges of the world shows .44 Colt bullet diameter at .443"
Phil Sharpe's handloading manual from 1937 says .448"
Neither even mentions the .44 Remington, which might be what started you down this path.