Here is a good thread about 5 shot 50 cal carry revolver:
http://thefiringline.com/forums/archive/index.php?t-280962.html
here is something I found on another forum:
"...You have to really pay attention to your zeros. The .50Spl is based on the .500Linebaugh, cut to .44Spl length of 1.16".
The .500Spl is based on the .500S&W, cut to ~1.27". Slightly shorter than the .44Mag but longer than "Special" length.
Then there's the .500JRH (or .500S&W 1.4") suitable for the FA and custom Ruger single actions.
Then there's the .500S&W cut to true "Special" length for use in New Model mid-frame five shot conversions. ..."
I heard of a guy who had Bowen make him a revolver based on 500 S&W brass but trimmed to 44 special length. I think they were calling it .500 special k(urt). Maybe they will eventually make guns chambered in .500 special w/ shorter cylinders and less weight.
I think the diameter of the base of the .500 Linebaugh based brass is larger than that of the S&W 500 mag based brass which can make the linebaugh harder to fit sometimes & I am not sure if there is is a slight diameter difference.
Anyway, the popularity of the 500 S&W has made greater availability of brass, bullets, dies etc probably making it the best basis for 50 cal rimmed cartridges.
It looks like any light-weight 6 shot 44 special, 44 mag or 45 acp snubby revolver that could be converted to some sort of short 50 cal 5 shot would start out weighing between 27 and 29 oz from looking at the Smith nightguards in those three calibers and that taurus 44 mag titanium. Would be silly to start out w/ a 40+oz revolver unless it was for the woods.