Blackout Ammunition .300 Blackout Subsonic 220gr Sierra MatchKing, 20 Round Box

The Subsonic 220gr Sierra MatchKing 300 Blackout 20 round box is the classic quiet load for the cartridge at $36.99, about $1.85 a round. It is the box to buy when you want to zero a suppressed rifle, test a new can, or find out what all the fuss about subsonic 300 Blackout is about. Match grade, factory new brass, about 1,030 feet per second.

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What the 20 round box is for

Twenty rounds is a zero and a group. It is the sensible first purchase of any new load, and for the Subsonic 220gr Sierra MatchKing it is also enough to measure how much your suppressor moves point of impact. Once you know the load suits the rifle, the 160 round bucket of the identical round costs less per shot.

Each box holds a plastic tray with 20 rounds, loaded in factory new brass with a match primer. The same lot control and final inspection apply as on every load we sell, and the round is gauged before it goes in the tray.

The 220 grain MatchKing

Sierra’s 220 grain .308 MatchKing is a boat tail hollow point built for accuracy. The jacket is thin and even, the core is weight matched and the hollow point is a manufacturing artefact, not an expansion feature. It became the standard subsonic 300 Blackout bullet because its length and mass fill the case capacity perfectly at 1,000 feet per second and because it groups as well as the barrel allows.

With a G1 ballistic coefficient around 0.62, it holds velocity well for a subsonic and drifts less in the wind than lighter bullets. It is the round most published 300 Blackout subsonic data is built on, and the one to start with if you own a suppressor.

Subsonic and suppressed: what changes

A supersonic bullet makes a crack as it breaks the sound barrier, and no suppressor can remove it. A subsonic bullet does not, so the only noise left is the muzzle report and the action. Put a can on the muzzle and the Subsonic 220gr Sierra MatchKing round is about as quiet as a centrefire rifle gets. Without a can the report is still a rifle report, only without the crack. the cartridge’s history explains why the cartridge was designed around exactly this pairing.

NIOSH puts the level at which impulse noise damages hearing at 140 decibels. A suppressed subsonic carbine is the one rifle configuration that gets close to safe without ear protection. Read subsonic versus supersonic 300 Blackout for the full comparison.

Velocity, energy and drop

Rounded from the 300 Blackout ballistics chart. Use the ballistics calculator for your own barrel. The useful range of the Subsonic 220gr Sierra MatchKing load is about 150 yards; beyond that drop gets steep, as with any subsonic. The barrel length guide covers how much speed each inch of barrel is worth.

Zeroing and point of impact shift

Zero at 50 yards for a general purpose suppressed carbine; the round will be close to 3 inches low at 100 and drop fast after. Fire a five round group with the suppressor off and five with it on, then record the offset. Most rifles move an inch or two. A match bullet makes that measurement trustworthy, which is the main reason to zero with this load rather than a hunting round.

If you also shoot supersonic, expect a different zero: a 110 or 125 grain bullet at 2,200 feet per second lands several inches higher at 100 yards. Many shooters keep a subsonic zero on the optic and a supersonic offset in memory. Our 300 Blackout versus 5.56 guide covers why the cartridge is chosen for this flexibility.

Gas gun cycling

Pistol length gas systems on 9 to 10 inch barrels cycle subsonics best. If a rifle short strokes with the can fitted, try a lighter buffer before anything else.

Why it is not a hunting round

At 1,000 feet per second the MatchKing does not expand. It behaves like a solid, cutting a caliber sized channel and often passing straight through. Sierra advises against hunting with MatchKings and so do we. For game or home defense use the 205gr Punisher Series solid copper or the 196gr fracturing round, both designed to open at subsonic speed. See our home defense guide.

Box, bucket and the hunting loads

The 215gr Berger box is the other match subsonic at the same price and worth trying alongside this one. The 300 Blackout ammo range and the buckets category hold the rest, and our bulk guide explains how to plan a season’s supply.

Getting the most from your first box of Subsonic 220gr Sierra MatchKing

Twenty rounds goes further with a plan. Fire three rounds to foul a clean barrel, because a freshly cleaned bore often prints a first shot away from the group. Then a five round group at 50 yards with the suppressor fitted, adjust the optic, and a second five round group to confirm. That leaves seven rounds of Subsonic 220gr Sierra MatchKing ammunition for a group at 100 yards, which tells you the real drop and the real accuracy of the rifle.

Write the results on the box lid: date, barrel, suppressor, zero distance, group size. When you buy the next box of Subsonic 220gr Sierra MatchKing, or move to the bucket, you have a baseline to compare against. If a later group opens up, you will know whether the rifle changed or the day did.

One more use for a single box: chronographing. Ten rounds of Subsonic 220gr Sierra MatchKing over a chronograph gives you an average velocity and a standard deviation for your barrel, and that number, not the one on the box, is what to enter into the ballistics calculator. A subsonic load with a single digit standard deviation is one you can trust at 150 yards.

What a suppressed subsonic sounds like

First time shooters are often surprised. With a good can and this load, the loudest sound at the shooter’s ear is usually the bolt carrier, followed by the bullet striking steel downrange. Bystanders 50 yards away hear a flat thump. The supersonic crack, the part of a gunshot that carries for miles, is simply absent because the bullet never breaks the sound barrier.

That silence is the reason the Subsonic 220gr Sierra MatchKing box sells to so many first time suppressor owners. It is the load that shows a new can at its best, because there is no crack to compete with the suppressor’s work, and it is cheap enough at $36.99 that trying it costs less than a range fee. Many buyers who come for one box of Subsonic 220gr Sierra MatchKing leave a month later with the bucket, a spare magazine dedicated to subsonics, and a second zero written on the scope cap.

If you are choosing between this box and a supersonic box as a first purchase for a new 300 Blackout, consider what the rifle is for. A suppressed rifle for quiet practice, night hunting alongside an expanding load, or home defense belongs on subsonics, and the Subsonic 220gr Sierra MatchKing box is the right start. A rifle without a suppressor that will be shot at distance is better served by a supersonic, and you can always come back to a box of Subsonic 220gr Sierra MatchKing rounds when the can arrives.

Shipping, tax and age

Ships to your home address in all 50 states. No tax stamp, no NFA paperwork, no dealer transfer and no tax added at checkout. Orders over $300 ship free. Ammunition is not an NFA item. Under federal law at 18 U.S.C. 922 no federal licence is needed to buy it. Buyers must be 21 or older for rifle ammunition and an adult must sign at delivery. Ammunition travels by ground carrier under the limited quantity rules in 49 CFR 173.63, never by air.

See the shipping and delivery page and the FAQ. Ammunition cannot be returned once shipped; the returns policy covers damaged deliveries. All loads meet SAAMI standards.

Start with a box of Subsonic 220gr Sierra MatchKing, learn what your suppressed rifle can do, and move to the bucket when you are ready.

Frequently asked questions

What is in the Subsonic 220gr Sierra MatchKing box?

Twenty rounds of 300 Blackout loaded with the 220 grain Sierra MatchKing boat tail hollow point in factory new brass, packed in a tray inside a retail box. Muzzle velocity is about 1,030 feet per second from a 16 inch barrel.

Is the Subsonic 220gr Sierra MatchKing round quiet without a suppressor?

Quieter than a supersonic, because there is no sonic crack, but the muzzle report is still that of a rifle. The load becomes genuinely quiet only with a suppressor fitted. It is designed for suppressed use.

Can I hunt with it?

No. MatchKing bullets are built for accuracy and are not designed to expand. Use the 205gr Punisher Series or the 196gr fracturing load for game and defense.

Why buy the Subsonic 220gr Sierra MatchKing box instead of the bucket?

To try the load before committing, to confirm zero, or because 20 rounds is all you need for a suppressor point of impact check. Once you know your rifle likes it, the 160 round bucket is about 20 percent cheaper per round.

Can this ship to my home?

Yes. Ships to your home address in all 50 states. No tax stamp, no NFA paperwork, no dealer transfer and no tax added at checkout. Orders over $300 ship free.

Is there a tax stamp on ammunition?

No. Ammunition is not an NFA item, so there is no stamp, no Form 4 and no waiting period, and we add no tax at checkout.

Will it cycle my AR?

With a suppressor fitted, usually yes. Without one, many gas guns need an adjustable gas block or a lighter buffer to cycle subsonics reliably. Pistol length gas systems do best.

Can I return it?

Ammunition cannot be returned once it has shipped, which is standard across the industry for safety reasons. Twenty rounds is the low risk way to find out whether the load suits your rifle and your suppressor. If it does, the 160 round bucket of the identical round is the next step and shoots to the same zero, so nothing you learned with the box is wasted.

You must be 21 or older to purchase rifle ammunition. Always use the correct ammunition in a firearm in good working condition. It is the buyer’s responsibility to know and comply with federal, state and local laws regarding the purchase and possession of ammunition.