Look at DSA Arms bravo Company Aimsurplus and CCMG
http://www.dsarms.com/DSA-ZM4-A3-Upper-Receiver-16-Barrel-Mid-Length-HG---ZM4CBUMID/pro...
Also look at reliability before accuracy...
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Of the Troops & For the Troops
Complete thread:
- AR Build Parts Supplier(s) - 
RidinLou, 
2013-06-29, 11:31 
- AR Build Parts Supplier(s) - Gunner, 2013-06-29, 12:03
 - AR Build Parts Supplier(s) - Miles, 2013-06-29, 16:31
 - AR Build Parts Supplier(s) - Bob Hatfield, 2013-06-29, 18:37
 - Look at DSA Arms bravo Company Aimsurplus and CCMG - Rob Leahy, 2013-06-29, 23:11
 - Selections based on bullet wt - RidinLou, 2013-06-30, 12:21
 - Not so much specific vendors...... - John Meeker, 2013-06-30, 17:02