Pulp Guns 2 and the 6.5 Mannlicher Carcano

[Z09SS]

I have hit an oddity...

The 30.71" barrel of a Fuclie di Fanteria Mo.1891 gets 5d+2 pi with 750/3,200. That 162gr bullet should be running about 2,295 fps.
The 17.75" barrel of a Moschetto Mo.1891 gets 5d pi with 850/2,900. Using the same cartridge as the rifle it's only getting 2,085 fps.

Why more half damage range?

Then there are the machineguns.

The 20.5" barrel on a Breda 30 gets about 2,000 fps from that same ammo but has 6d pi and 900/3,600.

Then the 25.75" barrel on a FIAT-Revelli fires it at about 2,100 fps yet gets 6d pi with 750/3,200.

Why is the fastest round getting the worst ranges?

[jacobmuller]

I'm ill informed but would the discrepancies be anything to do with rifling and bullet design? I know you experts can tell me which weapon firing which bullet will give what accuracy and range from just the 5.56mm family and it's all down to rifling and bullet design.