Big6ft6, I'm almost 100% certain your grandfather's gun is .44-40, not .44 Russian. That's the good news, since it's easier to get modern empty cases and the round had more power, etc. But I don't imagine you or your grandfather plan to shoot it.

His gun has replacement (homemade?) wooden grips, as the originals were either red or black molded hard rubber, which I have on mine.

My personal opinion is that if these guns are sound, in-time, and not all worn out, they are safe to shoot with low powered loads made just for them. But there is little reason to do so, considering the way their value has been increasing.

I have the identical gun, but in .44 Russian. I just got it out to compare with your picture. Your flutes and cylinder OAL are noticeably longer, by around 1/10". If you look inside the chambers, you will also see that they have a slight necked forward end, as .44 WCF, aka .44-40, has a slight shoulder.

I love this model. I shoot mine now and then with a mild smokeless load (Yes, I know, I know.) which gives less pressure and slightly less recoil than the correct black powder load, which I have also tested in it. This 130 year old gun delivers roughly the same power as a .45 ACP 1911 Colt pistol. I load a bullet cast from an original mold for the specified .44 Russian cartridge. Diameter for this one is .429", just like .44 magnum. I believe I'm loading the same diameter for .44 WCF, like your grandfather's gun.

If you are somehow able to obtain the gun, I think you will find it to be a real treasure, strong, very well designed, and a true classic S&W. You might be able to obtain original grips for it, but that would be a long and expensive road. And there was minor hand fitting of the grips at the factory.

Oh yes, I bought mine from an elderly farmer with a table at a small gun show in Annapolis, MD, about 30 years ago...for $165. Couldn't get the price lowered, so I bit the bullet and paid the asking price. He was happy. I'm more happy, with each passing year. I hope you and your grandfather can work something out because that gun, even without original grips, is a real keeper and, in this case, it has family provenance.