Atomic .223 Remington/5.56 NATO 77gr TMK, 20-Round Box

The Atomic .223 Remington/5.56 NATO 77gr TMK, 20-Round Box (brand part no. 00459) is a .223 Remington/5.56 NATO range and training load from Atomic, priced and built for high-volume practice without sacrificing reliability. Each round drives a 77-grain Sierra Tipped MatchKing (TMK) polymer-tip bullet at roughly 2600 fps out of the muzzle. It is a dependable option for anyone stocking up on rifle ammunition.

Key Specifications

• The chambering is .223 Remington/5.56 NATO, a common, affordable chambering that keeps practice costs down.
• The bullet weighs 77 grains, a standard weight that mirrors common carry loads for realistic practice.
• The bullet is a Sierra Tipped MatchKing (TMK) polymer-tip, a polymer tip that initiates expansion instantly on impact.
• The match-grade bullet jacket and core are held to tighter tolerances than a standard hunting bullet, which is what tightens groups at distance.
• Muzzle velocity runs about 2600 fps, consistent enough for predictable practice at the range.
• The case is Brass, the reliable standard for consistent chambering and reloading.
• Each box holds 20 rounds, a practical count for a range session without constant reordering.
• Cost per round runs about $1.58, useful for budgeting a range day or a season of practice.
• A case holds 10 boxes (200 rounds total), letting you order in bulk without repeat checkouts.
• Muzzle energy runs about 1,155 ft-lbs at the muzzle, giving a snapshot of the load’s downrange punch.

Frequently Asked Questions

Is the Atomic .223 Remington/5.56 NATO a defensive round or a practice round? It’s a target and competition load, built around a match-grade bullet for the accuracy and consistency serious shooters demand rather than hunting or defensive use.

Does the Sierra Tipped MatchKing (TMK) polymer-tip bullet expand on impact? Yes, it’s engineered to expand reliably on impact for a wider wound channel and faster energy transfer.

What is the case made of? It uses a brass case, the reliable standard for consistent chambering and reloading.

Buy the Atomic .223 Remington/5.56 NATO

High-volume practice is where good habits get built, and this load is priced to let you put in the reps. Browse more rifle ammunition while you shop, or add this load to your cart now. Order from our Lubbock, TX gun shop and it ships fast to your door.