This receiver is meant for .223, 5.56, .224 Valkyrie, 300 BLK and 6.5 Grendel calibers.  Port opening is not large enough for 450 Bushmaster, 458 SOCOM or 50 Beowulf.  

Made from 7075-T6.  Anodized black.  Comes with forward assist kit & dust cover installed.

• Made from billet 7075-T6 aluminum
• Mil-Spec Type III hard coat anodize 
• 'SHARPS BROS.' discretely engraved on both sides
• Weight: 9 oz

Sharps Bros. Sbur03, Billet Upper Receiver, Fits Ar15, Black Finish, Includes Forward Assist And Dust Cover Sbur03

Model: SBUR03
Product Type: Upper
Finish/Color: Black
Fit: AR15
Description: Billet