What are your thoughts on polymer AR lowers?

[Great-Kazoo]

I've been interested in these for several months and have been too afraid of them due to concerns of holding up to the concussive effects of firing and general wear.

It sounds like (from the experience of members here) that my fears are unfounded. I think I'll get one or two (not right away) and try them out as well. I've been wanting to build a cheap (yet safe) AR for my son and this just might be the solution.

Are they specific about use with .223 versus 5.56?

the only wear issues would be at the H/T/S pins and take downs. Yes you have movement in the buffer tube area. Every other wear issue is related to the function of the upper.
The SO's build is a CavArms lower onn a lightweight bushy upper. have not had any issues even when shooting suppressed. I did find by notching the buffer retainer i did not experience the issue of the buffer riding over it.

[RARGUNS]

As somebody who sees ARs in all lengths of service, I can say the vast majority of AR owners don't ever wear out a lower. If these lowers have have the life of an aluminum lower they will be fine for 75% of AR owners.

[Not_A_Llama]

Just to clarify - these are not at all like Cavarms lowers. Cavarms is pretty proprietary, with integrated pistol grip and stock, and funny takedown pins. Plumcrazy (not creek) lowers are essentially like conventional Aluminum lower receivers - they use the buffer parts, trigger pins, metal bolt catch from a regular AR, but everything else is polymer.

The receivers are definitely not machined plastic chunks, not UHMWPE, and not delrin. They look to me to be glass-filled injection molded nylon (a pretty wide range of materials). I don't recall perfectly, but I feel like the firecontrol had a more "greasy" feel to it - maybe UHMWPE there.

I was quite skeptical (especially of the plastic FCG) when I first purchased mine, but it worked very well.