I had good luck with Remington factory ammo, 240 gr JSP's. I also had good luck with handloads using 24 gr of H110 and 240 gr JSP bullets. I'm not sure if this qualifies as a "hot load", but it is near maximum. No, you won't get the gas mechanism to cycle with reduced or target loads.
The Ruger carbine is fussy about case overall length. While 1.610" is supposed to be acceptable for .44 Rem Mag, I had trouble unless the COL was closer to 1.590" (which matches Remington JSP, strangely enough). Some JHP's achieve 240 gr by lengthening the bullet above the cannelure, which can cause feed troubles with the Ruger carbine. OK for revolvers.
Speer makes JSP bullets in 240 gr which allow closely matching the Remington factory performance and dimensions, so I'm going to stick with this.
Other than being fussy about ammo, they are great little guns.