I’ve been running a couple polymer 80% ar lowers for a while now. After an inspection I found something interesting...
There’s a polymer 80 (gen 2) that has been used to build a 300 blackout carbine that has a little over 100 rounds through it and developed a hairline crack at the top of the buffer tube threads right where the charging handle comes out of the upper. (Pictured with stock and buffer in place)
The other is a genesis cnc (with the brass threaded inserts) polymer lower that has about 200 rounds through it in 5.56 with both 16” and 20” uppers and developed a crack in the same place. (Pictured stripped).
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There’s a polymer 80 (gen 2) that has been used to build a 300 blackout carbine that has a little over 100 rounds through it and developed a hairline crack at the top of the buffer tube threads right where the charging handle comes out of the upper. (Pictured with stock and buffer in place)
The other is a genesis cnc (with the brass threaded inserts) polymer lower that has about 200 rounds through it in 5.56 with both 16” and 20” uppers and developed a crack in the same place. (Pictured stripped).
Sent from my iPhone using Tapatalk