ETA: Don't bother getting one for a 22 or 9mm project, unless you're willing to spend more to swap out the plastic fcg for a regular one.
The plastic hammer/hammer spring combo is too stout to be cycled by .22LR, so you'll have a single shot.
The plastic hammer is too fat to fit inside a standard 9mm bolt, so you'll have a no-shot.
I'm planning on doing a live-fire evaluation next weekend when my 5.45 upper comes in, to keep the ammo cost of a thousand round torture test down.



Industry Partner New Frontier Armory is offering their iteration of the polymer lower, the LW-15, for the low, introductory price of $99.99, for a complete lower, including buttstock.

I ordered one in to test head-to-head against a plumcrazy polymer lower (which NFA calls the C-15, but as of my last phone/email, they no longer offer for sale). Since they've discontinued the C-15, there will be no comparison, just a two part post on my impressions of the unit I received.

This is, indeed, a complete, functioning lower receiver assembly with buttstock. Mine has the polymer fire control group, and a cheap, 6-position commercial telestock. Exterior finish is nice and even; a slightly rough matte black.

Overall: As with the plumcrazy lowers, the molded halves of the receiver appear to be sonic-welded together. Mold flashing is evident everywhere, even on the molded plastic trigger of the FCG and front of the magazine well. The only place flush on my unit is the top of the receiver where the bottom of the charging handle slides. Fit feels tough, barely flexible, and sturdy. Unit rattles loudly when shaken, with or without an upper mounted, owing to the telestock. Standard commercial tube mounted has metal receiver extension, standard carbine buffer and spring, and metal latchplate. The stock slider is loose, and will cam side to side and slightly back and forth, which accounts for the rattling noises. When shouldered firmly, the stock feels solid. With a sling mounted, and carried or shouldered by it, the stock rattle is noticeable and annoying. Measured assembled weight was 1lb, 11.4oz (27.4oz)

Right side: Mfg's markings "New [logo rifle] | Frontier | ARMORY, LLC | N LAS VEGAS, NV USA | LW-15 CAL. MULTI" are molded, slightly sunk-in (except for the logo outline which is slightly raised), on the right side of the magazine well. Mag fence and pivot pin detent boss are as with the plumcrazy - short boss for the pin, and reverse "C" molding around the mag release button, that does not connect to the boss. Right side of the (reversible) selector has a molded-in arrow indicating selector position, but there are no position markings on the right side of the receiver.

Closeup of right side, showing plastic selector detent with pistol grip partially unscrewed to take tension off the selector


Left side: No markings on the magazine well. "SAFE" and"FIRE" molded in small raised letters around the selector. Serial number on a small metal plate affixed to receiver underneath the selector, and flush with the receiver's surface.

Interior: No wasted plastic making the inside look exactly like a semi-auto lower machined from a forging. In fact, interior dimensions are basically M16-spec. Licensed Class 2 manufacturers may wish to note that these lowers do not have to be profiled as part of a post-sample machinegun conversion. It's also roomy enough to fit a registered lightning link or drop-in auto sear, for those who own such registered MG conversion devices. However... this lower has no shelf of any kind, so additional support or a setscrew to clamp your DIAS to the takedown pin post of the upper may be required to keep such conversion devices in place. Inside it's a tight, min-spec fire control well, slightly thicker over the takedown pin/selector/selector detent area, but still able to fit the takedown pin post, and an RLL or RDIAS. There is enough front-to-back clearance for the RLL to function. The pistol grip hole does not break through to the interior of the lower... the FCG well has a flat floor except for trigger hole. There is no evidence of mold flashing inside the seams of the firecontrol well.

the fcg well interior


Parts: Most of the LPK is plastic, except for the springs. As noted previously, the telestock is pure commercial (and slightly crappy), but the rest of the parts kit is custom plastic, except for all-metal springs, which look to be AR-15 LPK standard, and metal bolt holdopen, metal bolt holdopen roll pin, metal mag release button, metal buffer detent, and metal trigger/hammer pins. The trigger/hammer pins are not standard parts, as they lack the middle groove for hammer j-spring catchment, and look and feel like max-spec thick parts. presume them to be .155. The plastic disconnector has a different profile than a standard metal AR-15 disconnector (presumably to allow for more bulk and strength in the plastic), complete with a different and much longer disconnector spring. The plastic hammer is very thick, except for a narrow channel meant to allow the use of a standard AR-15 hammer spring. The hammer is really, really thick - more on that later.

Compatibiity: In the interests of compatibility testing, I completely disassembled the lower, except the (plastic) takedown and pivot pins and detents, and the bolt holdopen, and reassembled them with a standard LPK, using both an AR-15 semi FCG and selector, and an M16 FA FCG and selector. I test fit, but did not drill for, a GI factory auto sear installation. All standard metal parts fit just fine, and the lower passed function tests appropriate to both FCGs. The LW-15 lower uses a molded-in trigger guard, so trigger guard parts were not test fit or installed. The trigger guard is fixed, and cannot be "swung down" like a regular LPK for ostensible winter glove clearance.

The A2 style pistol grip looks to be a regular old part, screwed into the lower with a socket head cap screw and lock washer, like any other lower. I got to loosen and tighten it a number of times, changing out the various selectors. The plastic selector is reversible, and feels pretty stable. Nice crisp click between fire and safe. Both the steel semi and steel full auto selectors were a tight, tight fit in the selector hole of the lower, but moved easily enough when installed. The plastic selector detent seemed to have taken a bit of wear with the steel selector bodies.

Pins and retention: The plastic FCG uses non-standard hammer and trigger pins. They seem FAT, and fit nice and tight. They have a retention groove to one side, but not a j-pin groove in the middle. The FAT plastic hammer instead has a split right axle race and molded-in lip that grips retention groove of the hammer pin. The trigger pin is retained by a leg of the hammer spring, as with the normal FCG. In my unit, the pins do not rotate, and everything seems to slide freely.

standard semi FCG on left/lower, plastic FCG right/upper. plastic mag catch parts left/upper


With the plastic FCG, there is a quirk: You can put the selector on "SAFE" without the hammer being cocked. Any attempt to manipulate the charging handle after that will fail, unless you manage to destroy the trigger/selector interface. IMO, this is a bad thing. When charged and the selector is set on safe, there is no movement in the trigger at all - that's a good thing. Trigger pull is light and pretty crisp. Reset is relatively long and mushy.

Uppers .223: I mounted a plain-jane 20" Colt AR-15 A2 upper to the lower. As advertised, they've cleverly aligned their holes or something for a "no slop" fit. The upper is tight, no visible gap, no shake other than the telestock, and yet you can still work the takedown pin out with just fingers. Ditto the pivot pin. Charging handle slides smooth and firm. passes function check no problems. So far so good.

Uppers .22: I stick a ciener kit in there instead of the regular BCG. First off, the charging handle won't come back. Open up and check - the mold flashing on the sides of that FAT hammer are preventing it from fitting through the slot in the conversion bolt frame. I scrape/rub and nudge things together. Eventually it fits, and passes the first function check. I cycle vigorously several times to see if things wear in better, and they do, but...... the conversion kit has settled forward a tiny bit, and two bad things are happening. 1) The disconnector does not catch the hammer if the trigger is pressed back during a charging cycle. If I SLAM it back, it goes far enough back to catch, but mostly not. Not sure how it'd do with live ammo, and there's a chance for hammer follow there. 2) I go to open the upper, and the bottom ledge of the kit frame has let the buffer slide past the buffer detent, and now can't lever the upper free of the lower. I persevere, pulling back on the charging handle to drag the kit frame back a bit, and succeed in separating the halves. The buffer springs out, and I reinsert it past the retainer.

Uppers .22 #2: I plop my dedicated CMMG evolution topend on the lower. Fits nice and tight as before. No slop in this bolt group, and all works as expected. A teensy bit tight going on with that fat hammer, but passes all function checks, and seems to work normally and reliably in dry cycling. No issues separating halves when I take off the upper.

Uppers 9mm: I stick my Olympic Arms 9mm upper on the lower, and cram in my sten magblock. Two halves won't even close. That FAT hammer is just too fat for this pistol caliber upper. I'm not gonna force them. Maybe someday I'll take a file, or sandpaper to the hammer sides, or stick it briefly on my mill, but for now, the polymer FCG is incompatible with Oly 9mm uppers. magblock seems tight, but since I won't be firing it in this config anytime soon, I just take it out.

last observations: The telestock has that fat plastic sling loop in the back. Won't take a GI metal loop clamp. Seems neat so far. I intend to take it out and live fire the crap of it in a day or so.

Pictures would be nice

And did I read this correctly that Plum Crazy or G15 is no longer being made?

I ordered one in to test head-to-head against a plumcrazy polymer lower (which NFA calls the G-15, but as of my last phone/email, they no longer offer for sale). Since they've discontinued the G-15, there will be no comparison, just a two part post on my impressions of the unit I received.

bump info added in OP

Nice report! I love the idea of polymer lowers, but I will not trust the polymer lowers until they start injection molding around some type of metal. There are many discussions over the billet thickness and the thinner forged strength. Most people go whatever because I have never heard of one breaking. Well, I have heard and seen the polymer. Hopefully, there is some more structural engineering into this lower. Please keep us informed...I would love to see polymers make some headway into this "sport?".

I just picked one up too. I live right down the street from them. I really hope it works on my cmmg drop in conversion, but it doesn't sound that way. Here is a quick video showing the lower. I too will post a report after shooting it!

LW15 Quick Video

I ordered mine on 1/27 and my FFL had it in hand in one week. Picked it up from my FFL Saturday.

So far I've only put an upper on it and handled it. For my purposes (a cheap beater gun) it loos like it will do the job. One initial impression is that mated with a 16" M4 profile upper the gun feels front heavy.

I will probably shoot it this afternoon and will let to guys know how it works out.

OK, I was on the fence but will be ordering as soon as I hit submit

For those in the DFW area, PM me if you want to save on shipping.

tag, also interested in this set-up

Ordered mine at 1:00, its on its way now. That is service, got a M4 upper just waiting.

Thanks for the quick reply but it is too late to tell them what I intended to use it for as I have already ordered two and they are on their way to KS already. I am glad to hear that a regular FCG will fit I was already figuring out how to make it work with large pin parts, would hate to void the warranty but a guy has to do what a guy has to do.....now I guess I don't have to.
Guido, is there any way to get the proper parts to allow the lowers to work with a CMMG 22lr upper?

I took out my CMMG .22 drop in conversion and used it on the LW 15 lower and it worked just fine with the stock fire control group. I took some video, I hope to post it tonight or tomorrow. It was the first time using that lower and it worked great! It is a bit lighter and the trigger pull seemed "shorter". I also noticed a more pronounced sound to the buffer spring. Overall I am happy with it.

Will do!