This isn't a bullet casting question but a question about cast bullets. A friend of mine has a Winchester 92 in 38-40 and is looking for bullets suitable for deer hunting. He wants a hollow point style bullet but we can't find any production HP cast bullets. So I have two questions:

Neither one of us is set up to do any casting but does anyone know of a company making a cast bullet like that?

The second question is, is it even necessary to use a HP bullet or would a standard FP or RN cast bullet work just the way they are? The concern on his end is that they won't expand enough. My thought is that lead is soft enough that it'll mushroom anyway and the diameter is large enough to begin with that it'll do plenty of damage.

Any advice?

Well, you really don't need a hollowpoint at all to hunt with, not at .40 cal anyway. I would go with as close as you can get to a WFN nose profile. While it may not be suitable for the .38-40, see the Beartooth 200gr. WFNGC bullet for an example.

The .38-40 started as a hunting round with flatnose lead bullets. No reason that deer would need anything different.
If there is any concern about more expansion from a .401 diameter bullet, then look up some of the cast bullet makers that make bullets for Cowboy Action. There are a few that specialize in soft bullets, which might be your best choice.

.38/40 dates from the days of black powder and not loaded hot. 15K LUP/ 18K CUP approx. Frankly, at those velocities, even out of a rifle, you cannot be certain a hollow point would open up. At the same time, 1/2 ounce of lead through the vitals and no deer is going to be too chipper, quick.

92 Winnie will handle the other option, "hi velocity" loads. These were much warned on the box to NOT use in the 1873 rifles. They used a lighter bullet to get the increase in velocity. A soft nose or hollow point should open up. Loads in Lyman data.

I would not be afraid to load up any .40 pistol bullet and go looking for deer, cvarefully. Cases are not the stoutest. 155s a bit light. 180s or 200's brought home much venison if you do your part. Cast "hard" or "medium" fine. Soft would lead a bit but your call. 200 yard gun? No. 75 yards and under and you got some cleaning to do-- gun and deer... Luck.

I've killed a few whitetails with Lyman's 401043 bullet, over BP in an 1892 Winchester chambered in .38WCF. Hit them in the heart/lung region, and you don't need hollowpoints, a .40 diameter hole lets air in and blood out very nicely.

Lots of cowboy action bullets out there that are roughly the same. Don't sweat the hollow point.