Recently I helped a friend with his AR-15. He had gotten a DPMS carbine cheap, but it was missing the rear take down pin, spring, detent, buffer detent, spring, and the buffer tube was damaged needing replacement. It worked so well that he later had me look at a New Frontier Armory polymer lower AR-15 he had gotten cheaper than the first. It was missing the rear take down pin detent, spring, buffer detent and spring. The problem was that the receiver's buffer tube threads were chewed up and beyond saving. He could order a new polymer receiver from New Frontier for $33.89 shipped plus $10.00 transfer, but then again he might run into the same problem and any money he saved buying the AR is pretty much gone ($6.11 saved over an alloy). The internals (fire control group) are also polymer, but the upper is alloy. I've seen other poly AR lowers that have metal re-enforced critical areas like the front and rear retaining pin holes and the buffer tube extension. I have yet to see any issues in these type of hybrid receivers. Do you think he should get another poly receiver? Replace it with an alloy receiver? Hybrid receiver? or just keep it as parts?
If you think a plastic or polymer receiver has benefits worth having, get one of those hybrids. Off hand, I can't name one for you, but I've seen them in fiberglas units. Mine are metal, so the problem doesn't exist.
Won't consider a polymer lower and not even fond of their use in rifles designed for them. Never even thought about buffer threads or other things like detents. I got my last two Aero Precision lowers for under $40 each with free shipping from PSA a while back. Dollar savings are minimal if you are patient and weight savings are negligible. Neither offset the decrease in ruggedness or serviceability to me.
Nothing wrong with Polly lowers, they do not have to deal with much of a load, BUT, they don't seem to be all that strong, which makes them a non starter! Had a Carbon15 once, neato rifle, but found I could build an all alloy carbine every bit as light, and never have a worry about strength! You would be surprised at how light you can get a billet upper and lower with a little creative milling and light weight parts! My lightest comes in at a svelte 4.4 pounds dry, show me a polly or carbon hybrid that light!
In the 80% build community, AR poly lowers are basically used for .22lr builds. There are plenty of pictures and Youtube vids showing how these poly lowers failing with just a few hundred rounds of 5.56/223 rounds being fired through them. Here is the best deal for a top notch forged 80% lower. I have ordered and received three of them,80% Lower
I've also seen some 80% poly lowers that took too much heat during the hog out stage. Warped into weird looking paper weights. I like the 80% concept, and have built a number of them for personal use and family, but as far as poly goes - no. Only if the stress points are reinforced with metal, and only for .22 LR builds.
I know I'm old but I just can't see poly considering the price difference to metal. Need the same tools either way.
Yup, the polymer composite parts are not worth it unless you're talking about a stock or a pair of chopsticks. Hell, even then I'd consider bamboo for chopsticks.
He was trying to go cheap with the poly AR, more of a "I'll sell it for a premium when there is another run on ARs" or a cheap hand off rifle to his brother-in-law. After reviewing his options, he said he'll wait until he finds a cheap alloy AR lower or just sell it for parts, although he offered to sell it to me for over double he paid which I not so politely told him to shove it and not to call me anymore. Especially since he never offered to pay for the parts for the first AR, never mind the second.
If you run into him please thank him on my behalf for confirming my thoughts on cutting corners and self centered douchebaggery in general.