I'm not a cowboy shooter, but I've owned a bunch of .38-40s since about 1955 and still own several. The first was a Win 1885 Hi-wall that I found in a collapsed line shack in the Ruby Mountains of NV in 1955 and still own. I have fired several thousand rounds thru it and it still is very accurate. Also have an 1885 Lo-wall I bought in Vermont in the late 1980s and had an OR gunsmith reline to new bore cond. Killed two whitetails with that, using what were essentially "cowboy loads." At one time .38-40 was considered a perfectly good deer rifle in the East, and you just have to shoot the critter in some essential part....once. I had a nice '92 full-magazine rifle in .38-40 for a while in the early '80s, but it got turned into a house payment before I got to kill anything but coffee cans with it.
Revolvers in .38-40 that have excellent bores are extremely accurate. They were most popular after the turn of the 19th Century and before the advent of high velocity .38 Spl. and .357 handguns in the late 1920s and mid-'30s. For some reason Colt kept the chamber and bore dimensions of the .38-40 very consistent over the decades--they don't jump all over the micrometer like the .45 Colt and .44-40. Perhaps it's because they didn't make enough of them to wear out the tooling like they did the more popular calibers.
I have mostly had Colt "New Service" DAs in this caliber and they have all been very accurate with factory ammo. I still have a 5 1/2" NS made in 1923 and a 5 1/2" Uberti "Bisley" and they are both tack drivers with the same bore and chamber dimensions--Uberti knew a good thing when they saw it.
Once Trail Boss was introduced, I've used nothing else for this caliber. My bullets are an LBT 180 gr. design with a huge meplat. Starline cases and Black Hills "Cowboy Loads" are an excellent start. Uberti still makes .38-40s. Dixie Gun Works still has some, both SAAs and Bisleys.
My only complaint about the .38-40 is that in short-barrelled revolvers it is LOUD. Wear your plugs or muffs!
