Lets see here.
Ammo--ammo stays good for a long time. I've shot Lake City Arsenal ammunition manufactured in the '60s Some of the Greek .30-06* ammo dates to the mid-'50s.
Ammunition pretty much stays good until it goes bad. How do you know it's bad? Pretty much it does not go Bang! when fired. Things that are bad for ammo: Fires, Floods, and flurocarbons. You want to be careful with solvents and lubricants around ammo (not obsessive, just careful).
Bullet weights are--in the US--measured in grains (1/7000 pound) by tradition. powder charges are also measured in grains (shotgun ammo includes a dram measurement by tradition as well).
In the days before "smokeless" powder, ammunition was measured by caliber and charge size, such as 32-20, which fired a .32 caliber ball from a case of sufficient volume to hold 20 grains of black powder. At the very end of the black powder era, the bullet weight was appended to differentiate the ammo, e.g. the .50-110-210 (.50 caliber, 110gr charge, 210gr bullet, often paper-patched).
European tradition is to just measure bore and case length, which is where we get 9x19 to differentiate the 9mm parabellum from say, the 9x18 soviet round, or 9x16, the 9mm kurtz or .380acp round.
On average, lighter bullets will often have higher muzzle velocities. Whether that has more or less perceived recoil is more related to what gun the ammo is shot from, and the fit that weapon has to the shooter.
Now, for a blizzard of round weights, you need look no further than revolver ammo. .38spl/.357mag ammo comes in 110, 125, and 147 grain weights (among others). Each of those has a different "feel" when fired from the same gun. The 147gr .38/.357 rounds were adopted in 9x19 as a way of 'slowing' any 'over penetration' the 115gr rounds might be said to have.
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* .30-06 refers to the 'US Government .30 caliber round adopted in 1906; this used a 172-176gr 'spitzer' (pointed) full metal jacket bullet. This differentiates it from the .30-03 of three years' earlier which used a 200gr round nose ball; and to separate both of those from the previous "gov't 30" the .30-40krag (a 30 caliber ball on 40gr of powder)