Is there any chance that I can get by with using pure lead for .38 wadcutters fired at 700-800 fps if they're well lubed? I'll probably be seating them over 3-4 grains of Trail Boss.

Maybe but I'd have a Lewis Lead Remover handy or at least some Chore-Boy.

Ditto. Depends a lot on how smooth your forcing cone and bore is, and how well said bullets fit their throats and bore, and the relationship between throat diameter and bore diameter, etc., etc.. You're on the right track though. Heck, I would try the pure lead bullets though and see what happens. "Nothing beats a try but a failure." If they don't work, sweeten the alloy a bit.

How do you like Trail Boss for wadcutter loads? I have only ever used the 'traditional' powders- Bullseye, Red Dot, Clays, etc., and have a can of Trail Boss that someone gave me.

I haven't tried it yet, but it works okay with the Hornady SWC HPs. I like it because it fills up the case so I don't get a stiff neck from bending over the loading block looking for powder. Actually, you could probably use a scoop with good results. Gotta try that someday.
Another thing I want to try is using it for low velocity rifle loads. Charles Petty did an article on that a while back and got great accuracy with jacketed bullets. The Hodgdon manual has loads for many rifle calibers with jacketed bullets as well as some lead bullet loads for cowboy calibers and handguns. Interesting stuff.
It's not as cheap as Bullseye, but you can still get 900 .38 loads out of a 9oz can.

I am casting mine out of linotype so that they penetrate more. I have an idea that
38 specials that penetrate would be a more effective defense load.
I just used some today to qualify for my concealed carry permit.
whelennut

you should have NO problems with that.

Originally the HBWC were made of really soft lead so it would form to the rifling and give very good accuracy. They still are used in match shooting.

WC with soft lead will work just fine.

Put a bit of tin in the alloy, it will harden a little bit and will make your casting easier.
Use a Lyman 'M' to open the case neck and flare the mouth. I polish the portion of the 'M' die that expands the case neck to get a tighter fit.
I do not use the expander buttons that come with the reloading dies.
I would size the bullets .3585 - .359 or what ever is a tight fit in your cyclider mouth/throats.
And I would use a good lube, one of the hard lubes by LBT or Rooter Red.

Jim

Years ago when there were more swaged bullets on the market, most were pure lead and loaded to about 700fps. I think I loaded mine to about 650,but it's been awhile