Ithe single six cylinder some what more head space and does not support the rim as well, but still does fire with .32acp and of course there is no extractor issues. The rim on the R73 around the cylinder would certainly be nice IF a primer backed out or ruptured on the ,32 acp. but I doubt that is an issue. The single six is a little harder to load with the shorter cartridge , compared to the longer revolver cartridges , but the massive single action hammer did fire them all very well , and the rod ejected them ok with careful positioning. I probably will not be using them in the 9" barrel Single six but can, they were not as accurate as my handloads of .32S&W in it. I used a couple different foreign and American brands for the testing but only a couple cylinders full each as I do no reload .32acp - yet, but I have 600 of them from various makers . I only have a Walther PP .32acp remaining, gave my Keltec .32 to a daughter last year, that's why the test. That and the .32 Silver tip 60 grain open up real well in the Walther PP which has similar barrel length to my R73. My NEF R73 gobbled the .32acp up like they were made for it and gave good accuracy hitting just a little higher than my .warm .32 S&W long hand loads. I got 950+- FPS at 10" from the muzzle with the Winchester 60 grain silvertips out of it. Negligible recoil ! The gun is beefy ! The large hammer and the heavy springs reall smack those .32acp hard . I think that is the problem with firing .32acp in the newer small frame revolvers; the hammers are lighter weight, the springs are weaker and the tolerances are tighter in chambers and headspace and the extractor stars are smaller in contact area to the rims. Currently keeping the NEF73 loaded with the Winchester 60 grain Silvertips I have on hand and I have a nice little leather Lawrence pouch type holster with a Sloan type hammer shroud that goes on a 1 1/2" belt for around the property uses , my 12 year old grand son has claimed it when his dad thinks he is old enough to carry it around their remote property. By then I'll load up some 115 grain wad cutters in the large amount of .32 S&W long cases I have. I have been unable to get the .32 mag ammo so far in last year. Go ahead and fire the .32 ACP in Ruger single actions and the NEF R73 .32 H&R mag ! certainly safe IMHO.