AR15 12.5" 300BLK Mr Barrel

Name: AR15 12.5" 300BLK Mr Barrel
Brand: CMMG
Availability: InStock

CMMG · Barrels

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Best price

$192.99at MidwayUSA

In stock checked Oct 1, 2026

Buy at MidwayUSA

Compare 4 stores

Where to buy

Store	Price	Availability	Buy
MidwayUSA Best price	$192.99checked Oct 1, 2026	In stock	Buy at MidwayUSA
Brownells	$215.38checked Oct 1, 2026	In stock	Buy at Brownells
CMMG	$199.95checked Oct 1, 2026	Check store	Buy at CMMG
OpticsPlanet	$193.49Salechecked Oct 1, 2026	Out of stock	Buy at OpticsPlanet

Prices and availability change often, so confirm on the store's site before you buy. We may earn a commission from these links.

Price history

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Lowest in-stock price in the last 30 days: $192.99 at MidwayUSA. Dashed line = out of stock. Tracking since Sep 27, 2026.

Show the prices as a table

Store	Latest	Lowest	Highest
Brownells	$215.38	$215.38	$215.38
CMMG	$199.95	$199.95	$199.95
MidwayUSA	$192.99	$192.99	$192.99
OpticsPlanet	$193.49	$193.49	$193.49

Since Sep 27, 2026.

About this part

The AR15 12.5" 300BLK Mr Barrel is a 12.5" 300 Blackout barrel from CMMG. It's sold by 4 stores (2 in stock), from $192.99 to $215.38. The lowest in-stock price in the last 30 days was $192.99 at MidwayUSA.

Fits and works with

Caliber: 300 Blackout · Shop matching ammo
Bolt: Standard AR-15 (5.56 / 300 BLK / .350 Legend) · Bolt carrier groups
Barrel length: 12.5" · Handguards

Specifications

Manufacturer: CMMG
Color: Black
Platform: AR-15
Caliber: 300 Blackout
Barrel length: 12.5"

From the manufacturer

Direct replacement for the standard .223/5.56mm barrel converts your AR-15 to the high-performance 300 AAC Blackout (300BLK) cartridge. The 300 AAC lets you upgrade your rifle to 7.62 x 39 ballistics, while retaining the standard AR-15/M16 bolt, carrier, and magazine at its full capacity, with no additional modifications. 1-7" rifling accepts bullet weights from 110 gr to 220 gr, and 5/8"-24 muzzle threads accept popular AR-.308 flash suppressors and muzzle brakes. Three models available, 16", 12.5" and 8.2" long and treated inside and out with CMMG's "Wasp" nitriding process for outstanding resistance to wear and corrosion. 16" barr Mfg: Cmmg SPECS: Hardened 4140 chrome-moly steel, Wasp nitride finish, matte black .750" O.D. at gas port.5/8-24 muzzle threads.