I own 2 Rossi lever action rifles. One in 38 spl. and the other takes 38 spl and 357. The 38 is very accurate and I would like to use it for hunting deer and Jaguars up to 100 kilograms, which are abundant in my area. Unfortunately components are hard to get by. I have plenty 38 cases and SWCFN 158 grain bullets, but only IMR800X propellant.
I wonder if it is safe to load the 38 cases up to 357 rifle limits.
The rifle is in like new condition and I am not really convinced that a revolver cylinder with its thin chamber walls can take more pressure than the heavily built Rossi. On the other hand the other Rossi in 38-357 cal. is with the exception of the chamber length, an exact version of the 38. I am asking for advice and tips from more experienced members and would be very grateful for information.

No. The .38 Special case has less capacity than the .357 Magnum case, which will raise pressure with equal amounts of powder. You'll have to work up your load carefully. 800-X will get you most of the performance that the best powders like 2400 and 296 will, but pressure increases very quickly with a small increase in the load. Best of luck.

Bye
Jack