American Made
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Need Assistance? Call us at 425.530.0837
10.5" 300 Blackout Upper 10" HD Quad Rail
On Target With
Savings Of
$100.00
Original Price $299.99
Sale Price $199.99
A hard hitting pistol upper chambered in 300 blackout. Perfect for keeping locked and loaded as a close quarters pistol/SBR or hunting coyotes in the woods. Capable of running supersonic ammunition or subsonic ammo (AR lower buffer spring may need to be tuned for load). Complete with a Tactical Quad rail to attach an angled foregrip, flashlight and other accessories.

AR15 300blk Barreled Upper Receiver Assembly:

  • Hardened Arms M4 Feed Ramp Flat Top Receiver
  • Black anodized mil-spec finished upper receiver
  • Feed ramps for increased feeding reliability on barrel and upper
  • T-Marked upper receiver
  • 4150CMV 300BLK Nitrogen Stress Relieved Barrel
  • Black Melonited Finish
  • Chambered in 300 Blackout
  • 10.5" HBAR Profile barrel with M4 Extension
  • 4-Groove, 1/8 twist button rifled blank
  • .750" diameter at gas block
  • 5/8x24 threaded muzzle/barrel
  • Low profile gas block
  • Barrel dimpled to secure gas block
  • Pistol length gas system
  • A2 flash hider
  • Carbine length 10" HD Quad Rail WITHOUT Endcap
  • Fits any mil-spec AR15 lower receiver.

Hardened Arms uppers are high end, accurate, head spaced, inspected and test fired prior to shipping. They are built using stringent specs, top quality parts and procedures to ensure maximum reliability and performance.

You are responsible for knowing your state laws regarding barrel lengths, pistol and short barreled rifle restrictions. A 20% restocking fee will apply if you cancel anytime after ordering or if you can not take delivery due to state restriction. Dealer programs are available on our website. Two year warranty against manufacturer defects. Finishes will wear with use, no warranties apply to finish wear.
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4150CMV Barrel Steel
Whether starting with our 4150CMV machine gun barrel steel or highly refined 416R stainless steel our barrels are a cut above the rest. Engineered for accuracy and durability they are double nitrogen stress relieved and sodium nitrate coated/melonited (raw stainless steel is polished with melonited extensions). Index pins that lock into the upper receiver are pinned into the barrel through the extension on melonited barrels meaning the extension will never come loose. Machined in house on state of the art CNC equipment we deliver a barrel with every spec carefully controlled for peak performance.
 
Rail Lock Free Float Handguard
Machining our handguards in house provides us the opportunity to integrate features not found on most rails in the industry. Our rail lock feature, is designed to dovetail around your upper reciever insexing to insure a perfectly aligned rail that extends over the end of the upper reciever enough to do away with the unsightly gap found on lesser quality rail to receiver match ups. Combined with 6061-T6 aluminum with class II type III, hard coat anodized finish to match our uppers, fit and finish are top notch. Hardened Arms has many rail styles to choose from that are both stylish and functional. Our handguard offerings include quad rails, reduced weight rails, ergonomic smooth rails, skinny competition rails and our innovative patented Lumashark(R) illuminated rail with high lumen lights built in. Hardened Arms rails come in a variety of lengths and choices to meet your mission specific needs. .
 
Attention to detail.
It's the attention to detail that sets Hardened Arms apart. Items such as our machined in house 'Jam Nut' ensure ease of changing muzzle devices and indexing flash hiders while being fully re-useable. Crush washers are a thing of the past as they are single use and can induce stress and cause problems if used improperly. Bull barrels use shims to time your muzzle device without adding to the diameter of the already rigid barrel.

Alignment dimples are also machined into your barrel at the same time the gas port is drilled to provide 100% accurate positioning of your gas block and to keep it securely in place in spite of recoil. We machine our gas blocks and adjustable gas blocks right here from 4150 US barrel steel to give you the strongest and most durable product possible..
Hardened Arms uppers are high end, accurate, head spaced, inspected and test fired prior to shipping. They are built using stringent specs, top quality parts and procedures to ensure maximum reliability and performance.

You are responsible for knowing your state laws regarding barrel lengths, pistol and short barreled rifle restrictions. 20% restocking fees if you cancel anytime after you order or can not take delivery due to state restriction. Dealer programs are available on our website. Two year warranty against manufacturer defects. Finishes will wear with use, no warranties apply to finish wear. Fits any mil-spec AR15 lower receiver.
 
515 Tucker Ave Friday Harbor, WA 98250 | sales@hardenedarms.com
Phone: 425-530-0837