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Posted: 3/9/2015 2:52:03 AM EDT
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I'd like to start with saying that this is not part of my own rifle, but a piece a customer brought to the gun shop my neighbor runs. The piece originated from a Bushmaster, I do not have a round count on it. He did mention that the owner was zeroing a scope on the base rifle, when after a few rounds accuracy took a dump, nothing would hit close to the target. He didn't even realize there was a failure until the rail section was later removed by my neighbor/LGS. The polymer at the gas tube entrance had failed and blown out.
I'd always had my doubts about polymer uppers but couldn't find much documentation on their failure, so I wanted to put this out there. 
I'm having a noob moment, pictures aren't showing up 
They're still clickable |
| I would MAYBE consider a 556/223 polymer lower for a build. maybe if I turned into a pussy and wanted to save weight. but there is not way in hell I would ever use a poly upper. a metal BCG riding through a poly upper with hot gases forced into via the gas tube, that shit is going to break at some point. |
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Quoted:
For their C15 uppers with the full length top riser rail and oval handguards. http://www.bushmaster.com/images/catalog/c15_zoom/AZ-C15R97F.jpg But yes, the poly uppers were never a good idea.... http://oi3.tinypic.com/1zpt8c5.jpg. http://i.min.us/ibV6xy.JPG http://i.min.us/ibQDLe.JPG Quoted:
Quoted:
Never seen an upper without the rail nubbins  For their C15 uppers with the full length top riser rail and oval handguards. http://www.bushmaster.com/images/catalog/c15_zoom/AZ-C15R97F.jpg But yes, the poly uppers were never a good idea.... http://oi3.tinypic.com/1zpt8c5.jpg. http://i.min.us/ibV6xy.JPG http://i.min.us/ibQDLe.JPG that reminds me of a video by clark and dave called the front fell off |
| I wouldn't want a poly upper or lower for a .22 build let alone a centerfire. A friend of mine has a .22 upper with a poly receiver and he wants to change it out for a "real" one. I removed the barrel off the poly upper so I could add a ejection port cover and when re torqueing the barrel nut I didn't feel comfortable even going to 35lb ft with as much as things were flexing. |
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