I own several Car 15's, both upper and lower made from polymer.  One (an M-4)  is dead reliable and accurrate.  The other, in handgun getup, chokes and sputters and I can't hit shineola  with it.  Gun Test mag has been having a little war in its readers write section, some saying they they aren't worth a dime, others stating they are super fine.  Could I get some feedback  as I truly love the carbine.  

foof...Hello from across the river. I have several non-metal upper/lower combinations in different configurations. After thousands rds I have had NO FAILURE(s) to report. Your complaint is not related to the composition of the upper and/or lower. What caliber are your shooting in your ParaOrdnance? There are alotta variables and caliber/load is critical info...so post what ya can, eh. Like caliber, hand/fact load, barrel length, buffer weight, hyd or spring, extension length, gas tube(if any) std/modified, type of brake, bolt & carrier type...info like that will help. Also...would ya clarify "chokes...sputters". Sounds like you're describing an old FORD! Thx...Bud