Blackout, 8.6 Blackout, 300gr Sierra MatchKing Subsonic Ammunition, 20 Round Box

This 8.6 Blackout 300gr Sierra MatchKing load is a precision subsonic round built for one thing: target accuracy. Topped with the legendary 300‑grain Sierra MatchKing. A name synonymous with competition‑grade consistency, and tuned for the heavy‑subsonic 8.6 platform, it’s the load to reach for when you want to see exactly what your suppressed rifle can do on paper.

Specifications

Caliber	8.6 Blackout (.338)
Bullet weight	300gr
Projectile	Sierra MatchKing (match)
Type	Subsonic. Match / target
Muzzle velocity	~1,050 FPS
Ballistic coefficient	.750
Barrels	Loaded for 8″, 12″ and 16″ with 1:3 twist
Quantity	20-round box

The Sierra MatchKing bullet

The Sierra MatchKing is one of the most proven target bullets in existence, and this 8.6 Blackout 300gr Sierra load puts it to work in the .338 bore. With a high .750 ballistic coefficient, the 300‑grain projectile flies efficiently and consistently, retaining stability through the supersonic‑to‑subsonic transition that the fast 1:3 twist is designed to handle.

That consistency is what separates a true match load from ordinary ammunition. When every bullet is built to the same exacting standard, your groups shrink, and this 8.6 Blackout 300gr Sierra round is built to deliver exactly that kind of repeatable precision.

Quiet precision at ~1,050 FPS

Loaded to roughly 1,050 FPS, this round stays below the speed of sound, so suppressed it produces no sonic crack and is exceptionally quiet. Pair that quiet with a benchmark match bullet and you get a rifle that whispers and still prints tight groups. Ideal for precision practice and quiet range work.

What it’s best for. An honest note

This 8.6 Blackout 300gr Sierra load is a target and precision round first. The MatchKing is engineered for accuracy, not for the controlled expansion a hunting bullet provides, so while it’s superb for groups and load confirmation, for hogs or deer you should choose a purpose‑built expanding load such as a fracturing or Barnes‑style projectile. For help choosing, see our guide to the best 8.6 Blackout subsonic ammo for hunting.

Why a high BC matters

The .750 ballistic coefficient of this 8.6 Blackout 300gr Sierra load is unusually high, and it isn’t just a number on a box. A high BC means the bullet cuts through the air efficiently, resisting wind drift and shedding velocity slowly.

For a subsonic load, that efficiency translates into more consistent flight and more predictable drop at the close‑to‑mid ranges where the cartridge lives. It is one more reason this match round earns its reputation for accuracy.

Match accuracy from a subsonic load

Subsonic ammunition is sometimes assumed to compromise on precision. This 8.6 Blackout 300gr Sierra load is built to prove otherwise. A genuine match bullet, loaded to tight tolerances and stabilized by the cartridge’s fast twist, can deliver groups that surprise shooters used to thinking quiet means inaccurate.

That combination of near‑silence and real precision is exactly what makes a load like this so satisfying to shoot through a suppressor, and why precision shooters keep it on hand.

A note on gas guns

This load is built for all 8″, 12″ and 16″ barrels with the correct 1:3 twist. As with any subsonic match load, gas‑gun shooters should be aware that repeated cycling can affect bullet seating over time, so rotate your magazines and inspect rounds. Bolt guns avoid this entirely and often extract the most accuracy from a match load like this.

Rifle and suppressor pairing

Run this 8.6 Blackout 300gr Sierra load in any properly chambered 8.6 Blackout rifle with the fast 1:3‑class twist, and pair it with a quality .338‑rated suppressor for the full quiet‑precision experience. Confirm a dedicated subsonic zero and let the barrel settle between groups when testing for accuracy. You’ll find suppressors and precision accessories at our sister store, blackoutammo.shop.

Why buy from Blackout Ammunition

We carry genuine, in‑stock 8.6 Blackout ammunition and ship fast to lawful destinations nationwide. Whether you want this Sierra match load for precision or a hunting bullet for the field, we can point you to the right round. Browse the full 8.6 Blackout ammo collection, review shipping & delivery, and see the FAQ. For the velocity and energy behind it, read our 8.6 Blackout ballistics guide.

Frequently asked questions

Is this 8.6 Blackout 300gr Sierra load good for hunting?

It’s a match/target bullet built for accuracy, not expansion. For hunting, choose a purpose‑built expanding load instead.

How quiet is it?

At ~1,050 FPS it stays subsonic, so suppressed it produces no sonic crack and is exceptionally quiet.

What barrels is it loaded for?

All 8″, 12″ and 16″ barrels with the 1:3 twist that 8.6 Blackout requires.

Bolt gun or gas gun?

Both work, but bolt guns avoid repeated‑cycling concerns and often deliver the most accuracy from a match load.

Getting the best groups

To wring the most accuracy from this 8.6 Blackout 300gr Sierra load, treat it like the precision ammunition it is. Let the barrel cool between strings when testing for groups, use a stable rest, and confirm a dedicated subsonic zero before you judge the load.

Pair it with a quality suppressor and a barrel chambered and twisted for heavy subsonic bullets, and this match round will show you exactly what your rifle is capable of. Order your 8.6 Blackout 300gr Sierra MatchKing today and find out how tight a quiet rifle can really shoot.

What is the ballistic coefficient?

This load uses a 300gr Sierra MatchKing with a high .750 ballistic coefficient, which helps it resist wind drift and fly consistently for excellent accuracy.

Is it loaded for short barrels?

Yes. It is loaded for all 8″, 12″ and 16″ barrels with the 1:3 twist 8.6 Blackout requires.

Stock up on this 8.6 Blackout 300gr Sierra MatchKing load while it is in stock, and pair it with a quality suppressor to experience just how quiet and accurate the 8.6 Blackout platform can be.

You must be 21 or older to purchase rifle ammunition. All ammunition ships via ground to lawful destinations only; it is the buyer’s responsibility to comply with all federal, state and local laws.