Basically a necked-up 7.62x39 but with much less taper, the 9x39 is a Russian military cartridge developed because of dissatisfaction with the terminal performance and penetration of 200-grain full-metal-jacket 7.62x39 subsonic ammunition
The .45 ACP, for example, has only a few loads that exceed 1,116 fps, so you can pretty much pick any of them and have subsonic ammunition
without having to pay extra for it.
They include lead-free for use indoors or where contamination is a concern; a "duty round" with an aluminum core designed to limit overpenetration; subsonic ammunition
for use with suppressors that limit the weapon's sound signature; blank and dummy rounds for training; and tracers that allow for viewing bullet flight path in low light.
This latter design is based on the real MP5 SD which featured a multi-ported barrel, surrounded by a suppressor shroud, and did not require the use of subsonic ammunition
for adequate sound suppression.
uses a 38 to 40 grain hollow point bullet moving at just under the speed of sound at 1,050 to 1,070 fps.
. After 15 months, the Optima is still operating on the original battery with no deterioration in dot brightness.
It contained three 9mm Mac 10 submachine guns, silencers, subsonic ammunition
and four electric fuse detonators - all military-style weapons.
It provides holdovers to 850 yards for supersonic ammunition and 400 yards for subsonic ammunition
Plus, if required, subsonic ammunition
can also be fired.
Removing two baffles reduces overall length to 9.54 inches and leaves the pistol hearing-safe with subsonic ammunition
The company recommends not shooting subsonic ammunition
without a suppressor because that could cause the rifle to "short stroke," resulting in ejection and feeding malfunctions, but I did it anyway.
With all centerfire suppressors, the use of subsonic ammunition
is heavily advised; supersonic rounds still create a 'crack' when breaching the sound barrier.