One Piece Poly Lower

[hill37]

https://www.thefirearmblog.com/blog/2020...r-ke-arms/ What do you think?

[mdram]

i am not a fan of poly, for most anything
yes i do own 2 handguns with poly lowers, i still dont like them if anything else is available

[A5BLASTER]

I will pass.

[Wheelhorse]

It likely won't be in "one piece" for very long.

[phishfood]

I am debating becoming a test pilot.

If anyone happens to follow InRange on YouTube, this polymer lower is an outgrowth of an AR15 project they did a few years ago.They used CavArms polymer lowers, but those aren't available anymore.

[biodsl]

I ordered a striped lower three months ago. As I understand it, Brownell's is filling complete rifle orders first and strip lowers will be last so I have a wait. They are tough.

https://www.youtube.com/watch?v=YQ451lbKW0o

[pinetreebbs]

Looks like a winner.

[montana]

Looks like a winner.

My one concern is if the stock will splinter,"which is a bad thing" during a catastrophic failure. I have not seen or read of any such testing. From what I understand, this is the down side of plastic receivers.

[LRRPF52]

My one concern is if the stock will splinter,"which is a bad thing" during a catastrophic failure. I have not seen or read of any such testing. From what I understand, this is the down side of plastic receivers.

What if you ran full auto mag dumps through it, multiple different uppers in full auto, ran over it with a Bronco, did push-ups using the most stress-inducing leverage points on the rifle, fired more full auto mag dumps through it, did pull-ups with it off a bar, then did more mag dumps, then butt-stroked a 6x6 beam, then dumped more mags through it?

Whatever they did with the polymer engineering on this, they knocked it out of the park.

[video=youtube_share;YQ451lbKW0o]https://youtu.be/YQ451lbKW0o[/video]

[grendelnubi]

I have had a Plumcrazy Gen2 polymer lower for a few years now. No issues, (not full auto however) trigger is ok, does have a fire control feature where allows you to select safety without it being charged, which I like. I think I paid around $90 for it, main reason I purchased it.....

[Gtscotty]

I picked up one of the KP-15 complete lowers recently. Haven't had a chance to shoot it, but it is very stiff, fits snugly on my mil-spec uppers (doesn't fit my Aero M4E1s), feels good and comes in ~1/2lb lighter than my carbine lowers and ~ 1lb lighter than my standard rifle lower. Overall it seems very nicely done, I'm looking forward to getting it out to the range.

[biodsl]

I picked up one of the KP-15 complete lowers recently. Haven't had a chance to shoot it, but it is very stiff, fits snugly on my mil-spec uppers (doesn't fit my Aero M4E1s), feels good and comes in ~1/2lb lighter than my carbine lowers and ~ 1lb lighter than my standard rifle lower. Overall it seems very nicely done, I'm looking forward to getting it out to the range.

Thanks. Keep us up to date, please. I ordered the lower specifically to build a WWSD 5.56 carbine. I probably just should have bought the complete rifle but it's always fun to build it yourself. I've had the upper together for a couple of months now and am looking forward to completing the lower. I'm still waiting for it.

[Gtscotty]

Sounds pretty neat, got any pics or build list for the upper? I haven't had a chance to take the lower out yet, but playing with it some, it seems really solid. With one of my lighter uppers mounted the total comes in right at 5.5lb naked with no muzzle device, pretty svelte. I'm guessing I can't post links to other forums on here, but I posted a bunch of pictures and some comparisons over on THR.

I was originally intending to get a stripped lower, but since Brownells is selling the complete lowers now and there's no ETA on the stripped lowers... all things considered, I just went ahead and bought what was available.

[biodsl]

No pictures but I'm following the build list provided by InRange. I used the Faxon 3 port Slimline brake as the Slimline 3 prong flash hider has been discontinued. It was difficult ponying up over $300 for the carbon fiber handguard but I wanted to follow their build

http://www.inrange.tv/wwsd

[biodsl]

My KE Arms KP-15 ploymer lower shipped from Brownells today. Hopefully I can have it together and provide some type of report in the next few weeks.

[Rkangel]

My personal problem with the KE is the same problem I had with the Cav Arms. You're stuck with the fixed stock and grip they give you.

Quality looks like it is there. I just like to customize my stuff. After all these are legos for adults.

[biodsl]

[ATTACH=CONFIG]17412[/ATTACH] [ATTACH=CONFIG]17413[/ATTACH] [ATTACH=CONFIG]17414[/ATTACH]

I received my KE Arms KP-15 lower on Friday and have assembled it. I purchased knowing there’d be some compromises, but wanted the weight reduction as I am using this on a pencil-barrel, 5.56 lightweight build. I haven’t shot it yet but here are my thoughts thus far.

It’s light. I weighed a standard Aero Gen II carbine lower with Magpul CTR stock. It came in at 38 oz. The KP-15 with the same trigger and buffer was 29 oz. I don’t know how else to save that kind of weight on a lower without spending $$$. Yes, there are lighter stocks than the CTR but it’s no heavy weight either.

You can assemble a stripped KP-15 lower with a standard lower parts kit. However, there are some propriety parts included with the KP-15 lower. Here’s what unique to this lower:

Take down pins
Take down pins are not stock pins and are NOT captured. They have the detents built into them and the lower is not drilled for standard springs and detents. I consider this the biggest con of the lower. To access your BCG, you end up with a pin in your hand. Don’t lose it! If you transport your AR-15 with upper and lower separated, you’ll have the added step of pulling pins, putting the rifle together and then re-installing pins. The pins come with the lower and spares are available from KE Arms.

Safety selector detent
The safety spring and detent are loaded from the top, not underneath the grip as on a standard lower. You can use a standard safety lever (I did) but removing it will require drilling it out. KE Arms offers a selection of safeties modified to work with the lower to ease removal. They also provide a proprietary detent. The spring from a standard LPK is used.

Buffer detent retention
The KP-15 does not use a buffer tube. The buffer and spring ride in a hollow in the stock.
The detent and spring are retained by a 5/64” x 1” roll pin (provided). I didn’t install this as I’m using a JP silent capture spring.

There is storage in the stock but it requires tools to access it. There’s no hinged butt plate like an A1 or A2 stock. KE Arms claims A1 and A2 butt plates will work but “may require some fitting”.

Most cassette-style triggers will not fit. My CMC did not. It appears the polymer is thicker and rounded where the trigger well meets the wall of the magazine well. I fitted the CMC by grinding down the front edge of the CMC housing to gain the clearance I needed, probably under 1/32”. Not the most elegant of solutions but I had it on hand and really didn’t want to spring for another trigger.

Here’s the page with detailed information about the pros, cons and assembly of the lower.
KP-15 Stripped Instruction Sheet (kearms.com)

I noticed Brownells is asking $109 for these now. I paid $89 when I pre-ordered. Considering it’s weight, strength, and the fact that you’re not purchasing a grip or buffer tube I thought it was a good price.

[montana]

What if you ran full auto mag dumps through it, multiple different uppers in full auto, ran over it with a Bronco, did push-ups using the most stress-inducing leverage points on the rifle, fired more full auto mag dumps through it, did pull-ups with it off a bar, then did more mag dumps, then butt-stroked a 6x6 beam, then dumped more mags through it?

Whatever they did with the polymer engineering on this, they knocked it out of the park.

[video=youtube_share;YQ451lbKW0o]https://youtu.be/YQ451lbKW0o[/video]

I have seen the abuse a Glock will take and keep on running. I have also seen the mangled hands of people when the Glock has a catastrophic failure. Rifles can be much worse. This still hasn't answered my question if they have tested the lower with a catastrophic failure. The aluminum lower will usually contain the blast and direct it downward in the examples I have seen. I have my doubts with a polymer lower. I disagree with the authors evaluation of the fractured lower saving the shooter from injury. I think the shooter was lucky, "compared to aluminum lowers staying together" directing the force downwards.. . https://sinistralrifleman.com/2014/12/23...r-control/ [ATTACH=CONFIG]17416[/ATTACH][ATTACH=CONFIG]17417[/ATTACH]

[biodsl]

Wow. I say they don't come anymore catastrophic than that. Understatement from the article: "Paul was visibly shaken". Ha! No kidding.

I think it's a safe bet that KE Arms has not catastrophically tested their lower design.

[LRRPF52]

I have seen the abuse a Glock will take and keep on running. I have also seen the mangled hands of people when the Glock has a catastrophic failure. Rifles can be much worse. This still hasn't answered my question if they have tested the lower with a catastrophic failure. The aluminum lower will usually contain the blast and direct it downward in the examples I have seen. I have my doubts with a polymer lower. I disagree with the authors evaluation of the fractured lower saving the shooter from injury. I think the shooter was lucky, "compared to aluminum lowers staying together" directing the force downwards.. . https://sinistralrifleman.com/2014/12/23...r-control/ [ATTACH=CONFIG]17416[/ATTACH][ATTACH=CONFIG]17417[/ATTACH]

Sorry. I must have overlooked your concern about catastrophic failure. I was thinking cracking like the normal polymer lowers have done.

I’m not aware of them doing destructive testing with overcharges, but they seem like the kind of guys who would love to do that sort of testing.

Whether aluminum or any other material for the lower, it’s best not to have a support hand near the chamber, like with a magazine well grip, for example.

The polymer they’re using is stronger than the CavArms lowers.

I’ve seen photos of aluminum AR lowers where the magazine well bent outwards, but the lower doesn’t bear the brunt of force in those events. The bolt normally gives out, with extractor bending or breaking, with gases escaping and finding the path of least resistance.

Magzines blow out normally, with floor plate and cartridges often spilling out all over.