DrummerBoy,

First I am not being 'smart' with this response. Really. But I do not really understand your points or questions.  But I will try to address what I think you are stating and where you are gathering your information.

The velocities that Mike Venturino gives are with bullet that he has on hand or available.  What you need to look at and compare are the bullet weights of the originals and their velocities.
40-60 used a 210 gr bullet Cartridges of the World list it at 1562
40-65 used a 260 "   "         "              "  "     "        "    "  "  1420
40-82 used a 260  "   "         "             "  "     "        "    "  "  1490
40-72 used a 330  "   "         "             "   "    "        "     "  "  1407

Yes the 1876 40-60 does appear to be a good general cartridge but compare it to the original heavier bullet cartridges.
Yes the original 1876 was a rifle ahead of others with its 45-75 but it was behind Marlin in producing a rifle to handle the Government 45-70-405 cartridge which was the overall marketing GOAL.  Understand the 40-60(1884); 45-60(1879) and 50-95(1879) did not come around until later years.  See dates behind each cartridge.

Now to your next statement.  It appears to me that you are confusing Lyman's reloading concerns over original BP made rifles/pistols compared to modern made capabilities.  Most information in Lyman manuals are reduced loads to protect themselves from people loading smokeless in Original BP firearms.  What you state as psi value are most likely for original BP firearms. Example of this is separate loads for 45Colt in Single Action Armies and Rugers.

Then you state but 44 Magnums are offer in these same designs 1873 & 1892.  You are confusing Original BP steel with re-manufactured designs (replicas) using more modern steel.  'If I understand your comments correctly'.... Truly sorry if I am mis-understanding your comments.

Hope this helps you somewhat.  Keep on reading you will learn a lot more info about the originals -- the replicas -- & reloading of such.

This is my comment to help you understand my 30+yrs of this.  I never put smokeless in an original firearm produced in the BP era(others may).  You need to learn when that 'timeframe' is for the Original rifle or handgun you would buy.  I follow the manuals for 'reproducing original velocities' using smokeless powders in all replica firearms, I buy.  I load all replicas with full BP loaded cartridges using originally designed bullet or Lyman copies, if I so desire.
 If the manufacture states that their firearm is rated for a particular cartridge like 357Mag or 44Mag, I will fire that specific cartridge factory load every now and then but I general reload staying at mid-range velocities because, it is what I like.
 

  DEACON 

YESSIREE Bob > (Uh, Bob Who??).  Tis fer sure running heavy loads will only sort of mitigate Blow-By. 

Blow-By is not as serious of a problem with that Heathen Fad Smokeless stuff some aficionados seem to be obsessed with, as it is with BP and Subs.  In point of fact, when shooting smokeless, rifles will run an entire match easily.  Not necessarily so with BP or Subs. 

I always get a kick out of when the Brass Pickers at a match look askance at my fired 44-40 brass 'cause it don't look like 44-40 brass.  Fun, you betcha. 

We'll get ya shooting some real decent powder yet Deacon.  Just hang in there   

Thanks for the tip on cartrigekits.com...never knew such a kit was out there...Im going to give it a try..all the best getting the burnside shooting.  S and S out of NY and Dixie Gun Works sells conversion blocks when they were in stock. Had a buddy get one last year and he had to get on a back order list and they eventually called him from dixie.

I limit by fouling by shooting full power loads, 7.5 grains of Unique under a 200 or 250 grain RNFP. And yup, I do have to clean em, but not as much as the guys with mouse fart loads.

I have a M1886 Winchester in .45-70 that has "CGH" stamped on the buttstock. (Don't have access to the S/N right now. The rifle appears to have been reblued at sometime. I thought I had a magazine article on the subject, but can't find it now.    The s/n does fall within the range of the ones according to the article.