Howdy
Yes, all Italian made rifles are proofed for the cartridge they are chambered for in government run proof houses. This will include the toggle action rifles, such as the Uberti 1860 Henry and replicas of the 1866 and 1873 Winchesters. And yes, European proofing standards are a bit more stringent than American proofing standards, so no Italian made rifle will leave Italy without having been proofed.
HOWEVER...............proofing only involves firing one of two proof load cartridges in a firearm. If the firearm survives the proof test, the proof house signs off and stamps the firearm as being in proof. But there is such a thing as metal fatigue. It is completely possible for metal fatigue to set in with critical parts if many, many, many maximum pressure loads are fired in a firearm. This could eventually lead to failure.
Case in point. A number of years ago a friend of mine bought a used Uberti replica 1873 chambered for 357 Magnum. When he got it home he discovered a hairline crack in the frame. He brought it back to the store and got his money back. Yes, this was a used rifle, and there is no telling how many rounds, were fired in it, or how much pressure they generated. Perhaps one double charge of powder cracked the frame. Perhaps 999 standard pressure 357 Magnum rounds cracked the frame. There is no way of knowing. However that is the one experience I know of about a 357 Magnum Uberti 1873 that had to be returned because of a cracked frame.
Getting back to lever guns feeding specific ammunition. All tube fed lever guns (the pump guns too) have limitations on the length of cartridge they can feed. Generally speaking, there are two types of feed mechanisms. The toggle link rifles use a carrier that rides straight up and down in the frame. Cartridges are presented to the chamber in line with the chamber, much like a torpedo being stuffed into the torpedo tube in a submarine. All the others, the Winchester Model 1892 and its replicas, the Winchester Model 1894, and Marlin 1894 models use a pivoting carrier that pivots to raise a round from the magazine to the chamber. Very generally speaking, a cartridge shoved straight out of a carrier and into a chamber will be less troublesome than one which is feeding the cartridge into the chamber at an angle. Think about the problems sometimes encountered with a 1911 pistol feeding rounds up the ramp into the chamber.
Often bullet shape has something to do with this. A semi-wad cutter bullet can be more troublesome entering a chamber at an angle because the sharp shoulder of the bullet can sometimes catch on the edge of the chamber. Generally speaking, round nosed flat point bullets, and truncated cone bullets will be more reliable feeding up a tilted carrier because they do not present a corner to catch on the edge of the chamber.
The 357 Magnum Uberti 1873 is one of the most popular rifles in Cowboy Action Shooting, particularly with the top competitors. Most of these guys are shooting lightly loaded 38 Specials out of their rifles. Yes, any toggle link rifle can have a problem with ammunition that has a short Over All Length. There is no cartridge stop on the carrier of a toggle link rifle, the magazine spring pushes a round all the way onto the carrier, and the round stops on the rear face of the mortise in the frame. The magazine spring is also trying to push the next round in the magazine into the carrier and the only thing stopping it is the round already in the carrier. The shorter the round in the carrier, the more of the next round will be protruding into the bottom of the carrier. There is a bevel on the carrier that shoves the protruding round back into the magazine as the carrier rises. But if the round on the carrier is too short, the next round protrudes too far for the bevel to engage it, so the carrier is blocked from rising. I know for a fact that most of these CAS hot shots are shooting 38 Specials, not loaded down 357 Magnum length ammo in their rifles. Yes, there is a limit to how short a round can be reliably fed through a toggle link rifle, but I do not have the number at hand right now. Suffice it to say, if a round is too short, the carrier will be prevented from rising. An experienced CAS gunsmith can modify the carrier so it can be used with shorter ammo, but there is a practical limit to how much they can change the bevel.
Regarding the 1892 model; yes stronger than any toggle link rifle. And again, there is a limit to how short a round can be fed through one. And again, I do not have the number at hand.
The only lever gun I own chambered for 357 Magnum is an older Marlin 1894 carbine. My wife was shooting it when she was shooting cowboy with me because she did not like how heavy my full length rifles were. I was loading 38 Special ammunition with truncated cone bullets with an OAL of about 1.445 and the little Marlin never hesitated feeding them.
