The type I Carcano is an interesting one as it used the 6.5mm Japanese round.
Changing to 7.35 Spitzer round in 1938 is woeful and 28 years after the British.
Volley sights were added to Lee Enfields for long range but it was certainly expected that new smokeless powder meant that combat was going to be 1,000 metre rifle duels and the British experience in the Boer War played that out. Which is why the P13 was tested and why the Ross rifle was a made for long range. The Carcano was remarkably unchanged for so long and the carbines were certainly small and light and handy. If the 6.5mm round nosed Carcano was so longed lived then I would say that's a weakness of Italian industry and not the strength of the gun.
Oilers were still on Japanese guns as well and thier are similarlity to Italian and Japanese guns. Feels to me anyway.
The Ross and the P13 were both designed and "adopted" (in theory anyway) at a time when the Machine gun had yet to make it's presence really felt. The rifle was still the primary weapon of the battalion or regiment. Even in 1914 many European armies only had 4-6 machine guns per battalion or even regiment. (the US had, for the most part,
four Bennet-Mercier machine rifles per
regiment in 1914)
Scale of equipment, tactics, doctrine and thinking changed fairly quickly in four years compared to the 20-25 years before WW I.
While a lot of thinking went on during the 20s (some of it nonsense) there was very little purchasing of new guns as budgets were small and nations were tired of war. Purchases increased and new weapons gained traction in the 30s due to the political situation/s. some of the WW I stuff wearing out, and the extra peacetime allowing for enough R&D to allow new designs to come out fairly well thought out and refined.
I would also note that even such technical advances as field phones or field telegraph could make a difference it how a battle was conducted. During the Boer war for instance the Artillery had to be able to see the enemy in other than seige conditions or else reliance was placed on semaphore flags or blinking lanterns or runners to correct fire for hidden guns. All are time consuming, limited as to how far the observer can be from the guns and thus limited in poor visibility.
With either telegraph or phone wires the artillery observer could be several miles from the guns. The guns could be well out of rifle fire range. Corrections could be more speedily given or artillery fire supplied to targets in front of a infantry battalion or regiment.
With the provision of 8-12 tripod mounted machineguns per battalion ( 24-36 per regiment?) the long range firepower of the battalion/regiment shifted from the rifle to the machinegun. Long range being 800 yds and up if not shorter, The provision of bipod mounted machine guns at squad/platoon/company level meant that fire could be under taken by these guns at 500-800 yds. The difference in ranges being pretty much the stabilty of the mount/s and nothing to do with the gun or cartridge.
Please note the US, British and Germans all introduced boat tail bullets to extend the range of tripod mounted MGs by hundreds of yds (extreme range went up over 1000yds ) French 8mm round already had a boat tail.
However the training needed not to mention the problems of observing the the effects of the fire (fall of the bullets) tended to put a damper on this long range use.
The adoption of the 81mm mortar (the British 3in was really 81mm or close enough) also tended to take over the long range fire mission from the tripod mounted MGs. or supplement them.
However to jump to the conclusion that the regular rifleman in the squad/platoon/company no longer needs to able to fire at even 300 yds (200 yd or meter battle sight) or more is quite a leap. It places a real burden on the squad/platoon/company machineguns and mortars (if an army is so equipped)