Home Forums Hunting & Shooting AR and Tactical Rifles KP-15 Monolithic Polymer Lower

This looks kind of interesting.


The history of polymer lowers is really interesting. Maybe its time has arrived?
This guy has some interesting videos.

Why?

I've had a stripped lower on order since February. Going to use it for a 16" build if I ever get it.

If you watch the videos, the main advantages cited are cost, weight, and reduction in the number of parts.

I've never really considered weight a factor in an AR. Having a lighter buttstock may make the gun unbalanced if you put any kind of beefy barrel or stiffer long railed forearm on it.

Yeah, these lowers are pretty much intended for pencil barrels. I have a Green Mountain 16" pencil barrel waiting on mine if it ever comes.

I think the guys behind the concept are pushing 16" Faxon pencil barrels as a standard build.

I’m going to pick up a couple. I like the idea. I do care how much my ARs weigh. Bargain compared to building a standard stripped lower and adding the RE and stock.

On this Brownell's video on the molding process they claim they can pump one out every 60 seconds compared to 35 minutes for milling a receiver. A technology change like this could have a big impact.

That's huge.

Now factor not making a buffer tube, pistol grip, or the whole annodizing
process aluminum needs.

The time to remove flashing is probably around 2 minutes if CNC is used.
Less if robotics were used to feed the mill.

Finally got my stripped lower today. Been on order since February. Weighs 18.5 ounces, as delivered. Hope to start sticking lower parts in it next week.

I use Tennessee Arms lowers if I want a light weight. It's the same polymer but there is a standard M4 tube and a collapsible butt stock. I have never weighed one so I don't know if I can beat auk1124's 18.5 ounces. I guess I should find a scale and find out.

None the less this is a good idea that has been improved on with modern tools, techniques and materials. As I recall the former maker built it out of carbon fiber and they had a problem breaking at the buffer tube.

kwg

The two previous iterations were all polymer and did not break at the buffer tube. This is basically just an evolution of the original design.

STarting in the early 2000's there was a company that I think changed it's name several times that was building the complete lowers and they would many times break at the tube or just in front of it. As I recall Cavalry Arms was the first successful version because they made their lowers out of polymer. The name of the company escapes me so I can't google it.

Anyway, the idea has come full circle and now that Brownell's has become involved I'm sure the finished product will now be successful.
kwg

I picked this up from a November 2008 entry on ARFCOM

STAY AWAY....

Hesse change to Vulcan. Then started Blackthorne. Now they are Velocity Firearms.

They keep changing their name but the lack of Quality stays the same.

I have redone many barreled upper that people got from Black thorne they seem to be put toghther by a monkey in the back room. And the monkey must have been drunk..

Cav Arms from Mesa AZ made the original monolithic versions. When they went under the molds went to GWACS in Tulsa, basically the same as the last Cav version. This new KE version looks like it is somewhat evolved but then I can't see the internals. Seems like everyone that tried to make a regular lower out of polymer found out a regular buffer tube caused too much stress at the rear, which seems to be avoided with the monolithic design and some judicious thickening in that area. .

Well, Brownells has their reputation on the line. I'm sure they did their home work and have a good product.

kwg

Two minor issues (quirks?) with this lower that I wasn't entirely aware of. There are two semi-proprietary lower parts needed. I say "semi-proprietary" because you can in fact use milspec parts, but it doesn't sound like it would necessarily be ideal.

1. The body of the lower is thicker at the location of the hammer pin. A milspec hammer pin would apparently work, but not be flush with the lower on either side. KE Arms makes an extra-wide hammer pin, available on Brownells or KE Arms websites.

2. I haven't looked at it close enough to figure out exactly why, but according to the instructions that come with the lower, a standard milspec safety that is installed in the lower will be permanent. Once in there, you can't remove it. KE Arms sells a special safety selector on their website that apparently has a special groove milled in it, that allows it to be removed. Brownells doesn't appear to have this special removable safety on their website for some reason.

I don't like the thought of putting a safety in it that I can't remove later, so I have a removable safety and an extra wide hammer pin on order from the KE Arms website. So once again I am playing the waiting game. Hopefully it won't be months to get these.

If I run into any more issues like this, I will update in case anyone is interested. Anyone thinking about ordering one of these should probably decide if they want the wide hammer pin and removable safety, and go ahead and order them at the same time they order their lower.

Gotta wonder why those parts aren't just included,
with a price adjustment.

They come in a complete lower. Poster purchased a stripped.

True, I failed to make that clear. I note KE Arms also sells a KP-15 specific lower parts kit on their website for 70 bucks, which in hindsight would probably be the way to go with one of these stripped lowers.

What do you think of the grip? Is it comparable to another type of grip you're familiar with?