utm fk

bullet board | February 2020 G&a 39
(aguilaammo.com), Beck (beckammunition.com), CCI
(cci-ammunition.com), Eley (eleyammunition.com), Federal
(federalpremium.com), Gemtech (gemtech.com), Norma
(norma-ammunition.com), RWS (rws-munition.de), Remington
(remington.com) and Winchester (winchester.com).
These loads are generally advertised as functioning semiauto
firearms. I can confirm that Aguila’s 60-grain bullet
does run most semiautos. The catch here is that it needs
a faster 1:12-inch twist rate to stabilize the long bullet.
Winchester offers an interesting .22 WMR subsonic load.
Anyone who has ever used a .22 WMR knows they can be
quite loud. This is a lower powered, but effective, option.
All of the Big Four ammunition manufacturers, as well as
Atomic (atomicammunition.com), Beck and Gemtech offer
a subsonic loading for the .300 Blackout. Bullet weights
vary from 190 grains to 220 grains. Most subsonic .300
Blackout loads use a 208- to 220-grain match bullet. Most
will function in a 16-inch-barreled .300 Blackout-chambered
AR-15. SBR-length barrels shorter than 16-inches will
function more reliably with a suppressor attached.
Atomic ammunition offers 5.56 NATO, .223 Remington,
curiously a 6.5 Creedmoor load, .308 Winchester and
7.62x39mm subsonic ammunition. A number of these are
offered with heavy-for-the-caliber bullets. Beck Ammunition
offers 5.56 NATO, .223 Rem. and .308 Win. subsonic loads.
A number of these use a monolithic copper bullet that has
a large hollow point and are advertised as expanding. Both
manufacturers suggest specific barrel lengths and suppressors
for reliable functioning.
Subsonic Firearms Most AR-15 manufacturers offer uppers
chambered in 300 Blackout. These uppers have been
optimized with gas port sizes and gas tube lengths that
will provide reliable functioning with commercial ammunition.
In general, if you want to build an AR-15 in 5.56
NATO/.223 Rem. or AR-10 in 7.62 NATO/.308 Win. you
will want to use a short barrel with the shortest gas tube
you can find. Due to the limited gas volume produced
by these subsonic loads, the closer the gas port is to the
chamber and the greater the bullet travel after passing the
port and exiting the muzzle, the better the gun will run.
Experimentation can also be done with gas port size or an
adjustable gas port.
Summing up The most commonly found subsonic ammunition
is .22 LR and .300 Blackout. Subsonic loads in 5.56
NATO/.223 Rem. and 308 Win. are not too difficult to find.
However, expect to have functioning problems with most
semiautos with the latter. They have a narrow window of
firearms setup where they will function reliably. Recently,
expanding-bullet subsonic loads have been introduced that
open up some interesting options for short-range hunting
and personal defense. If you are interested in subsonic
shooting, you now have good commercially loaded ammunition
available. For the highest levels of function reliability,
I recommend getting a suppressor.