Carbon Fiber AR 15 Lower

I would think so considering there are plastic ones out now and a lot of 80% plastic lowers out, I would definitely install anti rotate pins, another option would be to install metal bushings if any holes became out of spec.

My father in law has a bushmaster carbon 15 and I have a polymer 80 one. Both have been fine doing casual shooting but I wouldn't grab either of them in a life or death situation. I think the only one I would trust for a real critical application would be a KE Arms or GWACS monolithic lower.

Just a point to clarify, when a company calls their lower a carbon fiber lower, what they really mean is it is an injection molded plastic lower but the plastic has some percentage of chopped carbon strands mixed into it. They should really be calling it a carbon reinforced polymer lower, but that doesn't sound as good for marketing so they call it carbon fiber. There is no commercially available lower that I am aware of that actually has carbon fiber layup like you see in aircraft or motorsports parts with the interweaved long strands of carbon.

Eaglegunz said:

what's the advantage of the carbon fiber

Click to expand...

Weight.

Keyfer 55 said:

Will a carbon fiber lower hold up for the long run. What brands are the best???

Click to expand...

I dunno about carbon but KE Arms' KP-15 glass-reinforced nylon monolithic lowers are extremely robust. Long as you don't mind a fixed stock and some minor peculiarities in regard to trigger/safety compatibility.

Eaglegunz said:

what's the advantage of the carbon fiber

Click to expand...

the tiny little strands of carbon added into the plastic increase the flexural modulus of the material greatly, which is basically how stiff the material is. It also increases the heat deflection temperature and the impact strength. Kind of acts like the rebar in concrete, but instead of having strands of rebar running the whole length it just has many millions of tiny little pieces mixed into it.

Most polymer pistol frames use a nylon plastic with fiberglass mixed into it, giving it the name glass filled nylon. The glass provide stiffness and tensile strength the same way carbon does. You can tell when a plastic part is glass filled because it feels heavy and cold to the touch because the glass is thermally conductive. The advantage of using carbon instead of glass to reinforce the plastic is that glass is much heavier than carbon.

I've no first-hand info to share on this subject, but there are a couple of good videos on Forgotten Weapons:





If you do a Google image search on the words 'polymer lower failure', you can see the weakness of non-monolithic polymer design attempts.

Very happy with my ke arms lower. 500-600 through it so far, no issues with polymer flashing in the buffer tube.

Don't do it.
A good forged lower is only slightly more weight.
I have a Carbon 15, from years ago.... it is now a 22LR dedicated. I even started worrying about the battering from the buffer against the buffer tube end, and the threads on the lower.
Look up broken polymer lowers / carbon fiber lowers...

https://www.google.com/search?q=broken+polymer+%2F+Carbon+fiber+AR15+lowers&tbm=isch&ved=2ahUKEwizrrfrqq33AhWDKX0KHXWWAfwQ2-cCegQIABAA&oq=broken+polymer+%2F+Carbon+fiber+AR15+lowers&gs_lcp=CgNpbWcQDFDoCVjIKGCLOWgAcAB4AIABO4gBsQSSAQIxMZgBAKABAaoBC2d3cy13aXotaW1nwAEB&sclient=img&ei=qZdlYvO1HYPT9AP1rIbgDw&bih=595&biw=1280&client=firefox-b-1-d

I would be comfortable with a KE Arms lower.

I tried a few different polymer AR15 lowers and ended up getting rid of all of them. They just did not hold up.
On the other hand I bought two Tennessee Arms AR-308 polymer hybrid lowers a few years ago and those are still working great even with the blast from a .308. I believe they reinforce critical areas of their lowers with copper which seems to make a difference. I used these lowers for a lot of bench shooting and some hunting and they have done well for me.

That said, probably the last dozen AR-308 lowers I've purchased have been Aero Precision M5E1 variants.

There are actually FULL Carbon Fiber lowers made from plate. These are screw together 80% lowers.

Keyfer 55 said:

Where do I find them??,

Click to expand...

I think you need to contact them. Not sure.. they were never really my thing.
https://nozirohsystems.com/