There are a lot of misconceptions about Carcanos that contribute to their poor reputation. Probably chiefly among these is improperly loaded ammunition. Carcanos are somewhat unique among 6.5mm rifles in that they have .268 bores. Unfortunately, the vast majority of the 6.5 Carcano ammunition that has been made over the years (Norma, Prvi Partizan, FNM, various reloads) are are loaded with the more common .264 diameter bullets. While many Carcanos will shoot these undersize bullets acceptably, many will not. The only two types of ammunition that I'm aware of that is available with .268 bullets are Hornady and Italian surplus. Italian surplus, IMHO, should only be bought for the clips if it comes on them as it is Berdan primed, corrosive, prone to both misfire and hangfire (I got multiple misfires per magazine when I tried it), and typically just as expensive if not more so than new production ammo. Hornady is unquestionably the best ammo as it's loaded with proper diamter bullets (Hornady also sells .268 160grn RNSP component bullets for the reloader). Prvi Partizan and FNM are OK, but they're loaded with undersize bullets so they may or may not shoot well (if anything, they're a source for boxer-primed brass). I see no reason to buy Norma unless it's all that's available as it's the most expensive and is also loaded with undersize bullets.
The other issue that plauges Carcanos' reputations are the crudely made wartime guns. Remember, the WWII started going badly for the Italians fairly early on and this is reflected in the quality of Carcanos produced during that time (they're comparable to the "last ditch" Arisakas and Mausers), early or pre-war Carcanos are of much better quality. Generally, the M1891 Long Rifles and M1891 Calvarly Carbines will be of higher quality than the M38 Short Rifles as the former two were produced in greater numbers before the war. My '91 Calvary Carbine was made in 1936 and is of similar quality to most other military rifles of the period. Generally 7.35mm rifles are less desirable than 6.5mm ones both because ammunition is even more scarce, and because the majority of 7.35mm guns were wartime production.
The only really legitimate complaint that I can find with the design of the Carcano is the sights. Later wartime guns are often found with rather crude fixed sights and my Calvary Carbine has somewhat coarse sights which are graduated at a very optomistic 300-1500 meters (an awfully long shot for a rifle with a 17" barrel and correspondingly short sight radius). Even so, with a bit of Kentucky windage I'm still able to shoot the rifle reasonably well out to 100 yards. I am fortunate that while Hornady unquestionably shoots the best, Prvi Partizan shoots acceptably from my rifle even with it's undersized bullets.
Finally, occasionally one will encounter a M38 Short Rifle chambered in 8x57 JS Mauser. DO NOT FIRE THESE RIFLES WITH SURPLUS OR IMPORTED 8MM MAUSER AMMO!!! These rifles were a desparate attempt by the Germans for a substitute-standard rifle that used their standard issue ammo and they are not up to the pressure of full-power 8mm ammo and there have been numerous catastrophic failures (i.e. KB's) reported when they're fired with surplus ammo, particularly Turkish surplus. Also, clips for the rifles are pretty well impossible to find (though I have read of people modifying standard Carcano clips to work). If you must shoot one of these, use either light handloads or the lighter loaded U.S. manufactured commercial ammo such as Remington Core-Lokts.
