1911 or so, believe it or not.
As to infantry techs, magazine-fed bolt-action rifles were roughly contemporary with the Maxim gun (
Lee-Metford was issued in 1888, same year the Maxim was formally issued to a German colony force and the
French Lebel was 1886), with the earliest models of bolt-action rifles like the
Remington-Lee and
Remington-Keene even seeing limited use well before it. You could probably merge the two into an "Updated Infantry Armaments" tech that unlocks the early MGs and bolt actions as possible inventions.
The current scheme I have for the Light Armaments branch is:
Flintlock Rifles: Bayonets, Ammunition Factories, 1800
Muzzle-loaded Rifles: Percussion Cap, Conical Bullets, Small Arms Factory, 1820
Breech-loaded Rifles: Needle Guns, Lever Action Rifles, 1845
Machine Guns: Metallic Cartridges, Volley Guns, Mechanized Reloading, 1860
Bolt Action Rifles: Magazine Rifles, Smokeless Powder, 1885
Modern Infantry Weaponry: Hand Grenades, Submachine Guns, Flamethrowers, 1905
The two biggest dilemmas I had in reworking the techs is how to balance historicity with the demands of gameplay and how to time things to, albeit poorly, represent iteration and proliferation. A lot of technologies had prototypes or early iterations that were used in periods before they actually became prominent (such as the Ferguson Rifle), but either owing to a lack of demand, being too expensive/impractical to produce at the time, or just too dangerous (guncotton), weren't viable for widespread adoption. Of course, the player is not bound to repeat history in a game, let alone in an alt-history scenario, so the compromise I've tried to go with is to have things time to (or around) the earliest practical iterations of specific technologies being where you unlock them - once you get the invention, iteration is implicit since V2 doesn't represent things qualitatively. So we don't need an invention for every single iteration of the bullet between traditional shot to the Minie Ball (whose early iterations are under the catch-all of Conical Bullets), while Machine Guns can represent everything from Gatling Guns and the Mitrailleuse to proper Maxims.