The Lyman 49th Edition Reloading Handbook divides rifles into Group 1 and Group 2, of which the Winchester M1892 is in the Group 2 catagory. According to the Lyman handbook, Group 2 maximum is 22,000 CUP, whereas rifles like the M1873 and Colt's Frontier Six Shooters should not exceed 13,700 CUP. There are a number of factors that need to be taken into consideration when handloading the .44-40. First, for best results, you should slug the bore to determine the groove diameter of the barrel. While the nominal diameter of bullets for .44-40 was .427" (rather than the .429" used in modern .44 Magnum guns), actual measurements of .44-40 barrels can wander all over the place. I've seen them run as large as .434"! The general rule for good accuracy with lead (and I would recommend sticking to cast bullets for the earlier barrels) is .001" over groove diameter. The problem there that may come up is if the barrel is sufficiently oversized, but the chamber is a "nominal" one, a properly sized bullet may made the neck of the case so big it won't chamber easily. A chamber casting using CerroSafe Low Melting Point alloy will be helpful, though you can also make up a "dummy" round and see how it chambers with the selected bullet. Another factor is the brass you select. Modern .44-40 brass can vary considerably in the thickness of the case wall, depending on the brand. Winchester brass generally has the thinnest walls, Remington brass is usually the thickest, with Starline somewhere in between. Personally, I prefer Winchester brass, but availability may affect you selection. Winchester's Cowboy ammo generally uses .428" bullets, and the loaded ammo isn't cheap, but it might be one way to get the brass. If you find you need to use .429" or .430" bullets, you should purchase a .44 Magnum expander die plug. This will help prevent collapsed cases from trying to seat the bigger bullet. Load-wise, follow the recommended powder charges. Fior CAS loads, you need to keep the muzzle velocity no greater than 1400 ft/sec., If you are loading for a revolver as well, the maximum is 1000 ft/sec, and such a load will be well below the rifle limit in your rifle. The .44-40 case was designed fro black powder, and as such has a lot of powder space with smokeless. A number of powders will work, but there will be a lot of empty space with proper powder charges. One owder that helps this is Trail Boss, which is bulky. Most of the medium-burning pistol powder will work well, including the old standby, Unique, or a similar one, Hodgdon's UNIVERSAL. W238/HP38 (same powder, different brand name, also will work pretty well. I always recommennd that the mouth of the case be crimped into a grease groove as firmly as can be managed without bulging the case away from teh bullet. Get a manual and read up on reloadding, if you decide to go that route.
BE SURE TO HAVE THE RIFLE CHECKED BY A COMPETANT GUNSMITH, WHO KNOWS m'92'S.