anyone still shoot sabotless 50cal ?

I depends on your barrel dimensions whether you might need a sizing die or no. You don't have much of a bullet selection. I have a 50 Cal Green Mnt barrel that I used about two years ago for a project to see if a muzzle brake would work with a sabot that didn't work to good. Also the Green Mnt 50cal is a.500 bore which made finding a sabot fit I actually had to size the bullet a little smaller to get a combination that fit the barrel'

I did have very good accuracy with Hornady 300gr .500SW bullets they only required a slight knurl because they are about .499 they will probably work in your barrel unless it is really big. The other draw back is the poor BC of this pistol bullet This is why everyone has gone to the 45Caliber and smaller guns they just perform much better than a 50Cal bore.

I am not following your variation of bullet diameter statement. I sure hope you are not seeing a .004 differene within the same bullet and you meant to say one was .498 and the other .502. Usually you see bullets +/-.0005 of stated even in pistol calibers so I'm a bit confused.

Running a standard .500 barrel blank such as your 500 smith would put you in the .492 range on the bore and would require FF. A .510 blank can be .500-.502 bore depending on manufacturer. Some of the true muzzleloader barrels including the savage ML2 are kind of all over the place.

I have shot both FF and smooth through my .510 barrel which is a .500 bore. I am running a one off system well off the traditional smokeless .50 path and it probably does not relate much to yours so take my results with a grain of salt.

I shot the 500gr hornady made for the 500 smith smooth right out of the box and they did not shoot well at all. I am wondering if the jacket was too thick to obturate well? They loaded beautiful on my Rock Creek bbl so whatever the bore is and that bullet O.D. is - they fit well.
I never tried anything lighter in a conventional pistol bullet but if I could get my hands on a few freebies I sure would.
You might give some of the Barnes bullets a go??? I would recommend you anneal them first for best chance at obturation.

I ended up going FF with an annealed .510 barnes bullets and have never looked back. The combo I have now likely shoots better than I am able.

My bro shoots Thor. He has a pretty tight barrel and also knurls the bodies. Plus he shoots kinda light loadings. Shoots good and kills great. Also working on an early ML2 that has about the tightest bore I've ever seen on a ML2. Must have been the 1st barrel made with that reamer. After I get it polished a bit I think it will do great with Thor bullets too = also lighter loads for a 115# woman.

Otherwise I only shoot 50 sabotless when firepolishing a bore. Like to use old Buffalo or Hornady Great Plains or TC Maxi ball/maxi hunter type lead bullets for that.

Safety 1st, shoot often, shoot straight. 10