Reforger 9mm NATO prefab "Ammo_9x19_Ball_M882.et" (and M9 pistol muzzle component) has the wrong specs:

mass 0.0075 kg
init speed 355 m/s
diameter 9.10 mm

The M9 pistol further modifies this with the MuzzleComponent having a "Bullet Init Speed Coef" of 0.970, so the bullet is only coming out the muzzle at 344.35 m/s, or 1130 ft/s.

All these specs are wrong. According to MIL-C-70508 (MILITARY SPECIFICATION, CARTRIDGE, 9MM, BALL,NATO, XM882), the specifications should be:

mass 0.00804 kg (124 grains)
diameter 9.017 mm
initSpeed = 375? (see below)

The instrumental velocity at 16 m distance was specified at 385 m/s ± 15 m/s from a 199.34 mm test barrel, which would correspond to a velocity of about 404.5 m/s at the muzzle of the test barrel.

But the barrel of the M9 pistol is only 125 mm long. According to the operator's manual (TM 9-1005-317-10), the muzzle velocity of the M9 pistol is 375 m/s (1230 ft/s). This is a ratio of 0.927 compared to the velocity from the 199.34 mm test barrel, which I find quite believable checking simulations from reloading programs (GRT) and various online chronograph results.

Whether the 375 m/s is correct or not, it seems the M9 pistol firing 1989-era M882 ball should have a minimum velocity of 366 m/s (1200 ft/s). Even with current-day Winchester 9mm NATO, which is supposed to be slower, one might expect around this much. American Rifleman magazine's August 1985 issue tested the new XM9 pistol and XM882 ball and obtained an average velocity of 1273 ft/s (388 m/s), noting "it is probable that service issue M882 ammunition, when available, will be of slightly lower velocity."

Note that the instrumental velocity of the M882 ball was reduced in 1998 from 385 m/s to 375 m/s from the same 199.34 mm test barrel (MIL-C-70508 Amendment 8, 14 Jan 1998). However, ARMA Reforger takes place many years before this.