You will notice some "fuzziness" in the way that the polyethylene structures are represented above. Sent it back. Jaybird, I am not sure what brand polymer lower you bought, but I have owned both the Plumcrazy and the New Frontier brands, and all have clearly stated “for use with the 5.56/223 caliber only!! What I have noticed here is that polymer is talked about as if it is all the same stuff. Put this toy near some heat and see how it holds up to forged aluminum or steel. Used in the form of fibers in rugs, blankets, and clothing, especially cashmere-like sweaters. If its a New Frontier lower I up you sent it back for replacement. 2009-2017 by At least in my particular application. Image Courtesy: 1. Because New Frontier Armory lowers don’t say that. It is holding up nicely. I do not believe this is a indication that poly lowers are bad I think I just happen to get a bad one. An additional quarter of discarded tires are ground into "crumb rubber" which serves as an additive to asphalt or as sports and playground surface, and in the manufacture of industrial products such as conveyor belts. Until both polymer lowers and uppers have steel or sometime of other high tensil strength reinforcing, they should be avoided for any serious AR use. Traditionally, much of the AR is already plastic. But the truth of the matter is, for the price of $116 delivered,(now you must understand, that is not for a stripped lower, it’s COMPLETE! It has been torture tested, kicked, dropped, made fun of and bullied. The plastics used in a home 3D printer are nothing like the polymers used on AR-15 lowers. Yep, that’s where one of the polymer’s failed (by the defunct Hesse) and right through the rear takedown pin hole (Of Course)-apparently, modification of the expensive custom injection mold wasn’t possible or affordable, so they put it up for sale. I think polymer lowers are here to stay and I think it is a good thing, lowering the barrier to obtaining an AR. Reminds me of accounts of craftsmen in Southwest Asia making functioning pot metal copies of the AK. http://www.youtube.com/watch?v=j4QIs3crPXc. Not pleased. They are not multi-caliber lowers. When was the last time anybody here saw a metal bodied portable power tool? “You would be better off carving a lower out of balsa wood.”. If you want light, get an M4 carbine profile or “pencil” profile barrel (most AR-15s these days have m4 profile barrels, so there’s probably not much weight savings you can make). I would have to say, “it depends”. Hundreds of poly lower owners have spent and wasted money on junk. Part of the reason polymer pistols work so well, is the lack of a buttstock component. .hide-if-no-js { I have 2 new frontier lowers. You get what you pay for. By the way, put one on a .50 Beowulf build and still no problems! The New Frontier Armory Poly lower gen II has been refined and My 6th one just came in. Use KNS non rotating pins will also probably help. Notify me of follow-up comments by email. A simplified model is proposed to describe this behavior which accounts for the effect of the normal load on the growth of the real contact area and the shear stress at the interface between the pol… Not many weapons can allow you to accurately put large number of rounds down range quickly. A "very low density" form (VLDPE) with extensive short-chain branching is now used for plastic stretch wrap (replacing the original component of Saran Wrap) and in flexible tubing. Additionally, American Tactical Imports produces its Omni lower which has realized good deal of success on the market, despite a few wavering reviews on its ability to pair with mil-spec uppers. High-ranking brass were accustomed to large, heavy, .30-caliber wood and steel rifles that felt more substantial. They may be good products – I am not saying they are or aren’t. Ok if were talking a major SHTF weapon an M16 is not the choice your gonna want. And I only wish they were $35 still! The melting of a crystalline compound corresponds to a sudden loss of long-range order; this is the fundamental reason that such solids exhibit definite melting points, and it is why there is no intermediate form between the liquid and the solid states. Thermoset polyurethanes have many advantages over plastics for a variety of applications, including: . It is one step below top notch. Aside from their high molar masses, how do synthetic polymers differ from ordinary molecular solids? I have a BUSHMASTER carbon 15 with about . The only problem I have had, was with the Plumcrazy lower, the take-down pin broke in half, I replaced both pins with mil-spec alum. Polysaccharides are polymers of sugars; they play essential roles in energy storage, signalling, and as structural components in all living organisms. Your discussions, feedback and comments are welcome here as long as they are relevant and insightful. There are many available, some with no rail up to those with quad picatinny rails for attaching all kinds of peripherals i.e. Its resistance to fatigue makes it useful for food containers and their lids, and flip-top lids on bottled products such as ketchup. It is also one of the simplest polymers, consisting of random-length (but generally very long) chains made up of two-carbon units. Polyvinyl chloride polymers are one of the most widely-plasticized types, and the odors often associated with flexible vinyl materials such as garden hoses, waterbeds, cheap shower curtains, raincoats and upholstery are testament to their ability to migrate into the environment. You are right David. Thats easily fixed by using a cheap sterl insert to take the direct stress away from the polymer. Nothing could be further from the truth. Put thanks again for your input. I have many of the same reservations for rifle polymer lowers, even though I own a glock. Describe the two general methods of polymer synthesis. I will never nor would I recommend anyone to purchase anything from them!!! Canada will also pay less for its new plastic money. Its molecules may consist of from 50,000 to 200,000 monomers. In short, the efficient recycling of tires remains a problem having no clear solution, desipite the considerable amount of effort being devoted to it. 1) Everything is a tradeoff. The polymer lower; however, is a great improvement in terms of weight and durability. Not near the buffer tube but on the right side. Home » Firearms » Is the Polymer Lower a Good Idea? With a lifetime warranty you can’t go wrong. Widely used for inexpensive packaging materials and "take-out trays", foam "packaging peanuts", CD cases, foam-walled drink cups, and other thin-walled and moldable parts. you really can’t go wrong. Less rigid than thermosets, thermoplastics can soften upon heating and return to their original form. When the army was developing the lieghtweight M-240 they used titanium on many places including the tripod mount point. One of the major breakthroughs in polymer chemistry occurred in the early 1950s when the German chemist Karl Ziegler discovered a group of catalysts that could efficiently polymerize ethylene. (not including add-ons) Thus the strength to weight ratio (as well as stiffness to weight ratio) of a carbon fiber part is much higher than either steel or plastic. If this type of narrow-minded thinking was the norm, we would still be living in caves. The M16 was great unless you had to buttstroke someone or in the situation just mentioned, a big rock shared the same time-space continuum. HDPE has mostly straight chains and is therefore stronger. In theory, only a single chain-initiation process needs to take place, and the chain-propagation step then repeats itself indefinitely, but in practice multiple initiation steps are required, and eventually two radicals react (chain termination) to bring the polymerization to a halt. That doesn’t really help your credibility. I am looking forward to CTDs evaluation. They are designed for multi caliber use. The metal rails on the lower of a Glock are there to elliminate wear based on material mismatch. The simple fact is, it’s not hard to build a long gun that can take virtually any abuse that can be heaped on it. I can’t say don’t buy one, I can just say I have had an issue and it was resolved quickly. For additional references, see this Google directory page. Thanks everybody for your input, just seems heavy I think a lot has to do with barrel… Maybe I was use to shooting the M-16 A2 A4 the M4 while I was in the service I don’t know… If it has to do with me not picking one up in a while or what.. We reserve the right to edit as appropriate, delete profane, harassing, abusive and spam comments or posts, and block repeat offenders. I think about 210 rounds will be a pretty good test. The sollution was to oversize the hole and use permanently bonded steel inserts for the pins to be inserted through. It was first used in the 1970s to replace steel tire cords. The AR platform is no exception. If SHTF ill be grabbing that. that should get it good and hot and any stress points should fail at that point. Artificial heteropolymers are more commonly known as copolymers. The bottom line is: Two parts of identical shape and size, one of which is steel and the other is aluminum – the steel part will be stronger given the strongest alloys were used in both. Josh, in response to your question, I guess it could be a number of things, but if your AR has a fairly common forged flat-top upper receiver, then I would look first at the type of barrel you have. This material serves as a binding and reinforcing agent, a pigment, and it also improves the thermal conductivity — important for preventing localized overheating. Brown, could you please expand on what happened to your ATI omni lower? So – its not just the material but how it is molded and the direction of the fibers. Then the polymers—long chains of molecules that make up a plastic—are recovered from the solution in solid form and reshaped into plastic pellets. – Plastic isn’t Polymer. Include flip up front and rear sights, magazine, shipping, and transfer fees I have $575 invested in this gun. I personally bought for plinking and r and D and am waiting to see the results. function() { When these first came out (I think it was the Plum Crazy lowers I saw first) I told my friend who has his FFL and ordered a few up that I think they’d make great .22lr plinkers. A variety of plants produce a sap consisting of a colloidal dispersion of cis-polyisoprene. Functioned first time, every time. Yes, I would like to receive offers and newsletters from Cheaper Than Dirt. That was a light, balanced, easy to shoot and carry light infantry weapon. One of these relates to the release of small molecules that act as hormone disruptors as described above. In plants, these glucose-polymer reserves are known as starch. I have an AR57 upper on one and a 5.45 upper on the other one. Whether or not the conditions and usage is close enough in your mind is up to you. I would certainly be open to the idea by taking in reviews like this, commentary from a website or community’s users and weighing the idea of taking a loss like this writer did for my own research. You can not compare the stress of a rifle round to that of a pistol. I really like the feel of it tho. Most recycling processes are optimized for particular classes of polymers. I have a DPMS pencil profile 5.56 upper pinned on an NEF polymer lower. Stephen Lower 2. Those Saiga Aks that are converted are unbelievable. A polymer lower AR would actually work best with the piston and recoil assembly are in the upper. The squiggly lines at the ends of the long structure indicate that the same pattern extends indefinitely. I like this little weapon, and as a truck-gun, closet gun, it should be great. Polypropylene is also crystalline and thermoplastic but is harder than polyethylene. The tacticity of a polymer chain can have a major influence on its properties. J-B Weld Plastic Weld Epoxy Putty Plastic Weld is a hand-mixable, fast-setting epoxy putty that forms a durable bond to most major plastic types. When uncolored, it is translucent but not transparent. You will never need to shim ANYTHING in this lower EVER. You dont seem to understand it is the whole lower receiver, complete, including butt stock, ready to pin in and fire with an upper. The problem is titanium is stronger than steel but its not as hard so steel pins would wear throuh the titanium and break it. The army is investing heavily in ceramic barrel research for their machine guns so I can see a day when most guns will be close to 100% polymor and ceramic. I had the NF’s pin at the buffer tube came out, but this can be fix. I have to comment on this comment by Glen: “I’m surprised to see that no one has mentioned the DIY AR15 lower project….all you need is the software and a 3D printer”. ... and for the story of how it all began, see Yasu Furukawa's Inventing Polymer Science: Staudinger, Carothers, and the Emergence of Macromolecular Science. Reciever extension stripped just like the above comments. The rifle must work every time you need it, and under all circumstances. Receiver owner claimed 5.56/.223 factory ammo. That would seem to be the sort of niche market that a polymer AR-15 would fill and compete in. Personally (not knowing you of course), I’d say you might be wiser to start going to the gym and building some arm strength. Of the 10, I’ve built 6 into rifles for friends and no problems so far. I would consider using a polymer lower on my next AR build. And the .5 lb wieght savings is insignificant. I am also a full time police officer and firearms instructor and my personal duty rifle is built on the FMK platform and it has held up to everything I could have put it through! Making critical firearm parts out of plastic is only for people that want to maximize profits or make cheap guns (or both). Maybe its the balance of your AR and not the weight. The starches in food grains such as rice and wheat, and in tubers such as potatoes, are a major nutritional source for humans. Those that are used for building materials (in mobile homes, for example) can build up in closed environments and contribute to indoor air pollution. Quick update on my FMK poly lower. Sure, Josh. Since it failed on you, and the lower comes with a lifetime warranty, why didn’t you send it back? First off, there is a HUGE difference between companies. Time and “use” will tell. The huge quantity (one estimate is 108 metric tons per year) of plastic materials produced for consumer and industrial use has created a gigantic problem of what to do with plastic waste which is difficult to incinerate safely and which, being largely non-biodegradable, threatens to overwhelm the capacity of landfills. I am not affraid to say, VULCAN ARMS SUCKS AND WILL NOT EVER STAND BEHIND THEIR PRODUCT!!! I was in on a buy of 10 frontier lowers and the only problem to date has been the take down pins. The evidence that many of these chemicals are able to act in this way at the cellular level is fairly clear, but there is still some dispute whether many of these pose actual health risks to adult humans at the relatively low concentrations in which they commonly occur in the environment. Make sure you thoroughly understand the following essential ideas which have been presented above. No “thank you” note or “sorry about that” note, just the part. Too much evidence exists for the use of polymer. It fired without fail, recoil was almost non-existant, and was just a pleasant little firearm to shoot. It is funny, if you go back to the story that started this discussion, the ATI Omni is one of the poly. Of course, tires are made of much more than rubber materials. In a world full of inexpensive, mass-produced black plastic and aluminum, there’s always something nice about handling those massive battle rifles built in a time when rifles were made by craftsmen more or less by hand from traditional materials. You might notice that it is becoming more difficult to find a modern duty pistol that isn’t made of 50 percent polymer. I am a rifle armor and custom builder. With a lighter lower the weapon is now barrel heavy. And what decomposition does occur will combine with rainwater to form leachates that can contaminate nearby streams and groundwater supplies. I replaced the buffer detent pin, applied loctite and then STAKED the plate into the castle nut- no more backing out, nothing “stripped”. Some major types are low-density (LDPE), linear low density (LLDPE), high-density (HDPE). Mosin guy, I completely agree. Both rifles have their own S&W M&P 15 lowers including Magpul colapsables which I like very much; however, I have used a NF lower with both of them and they both work just as well after a couple hundred rounds through each one. If you do these things, combined with a lightweight polymer lower, you can easily have yourself a 6lb rifle! The biggest question people have with polymer AR lowers isn’t usually the fit of the product, it’s the durability. New frontier sells a house brand metal lower machined by areo precision that is a much better deal. ); It depends on what you are going to use the rifle for. lowers from New Frontier and I currently own the Plumcrazy poly. These are regions of the ocean in which a combination of ocean currents drives permanent vortices that tend to collect and concentrate floating materials. 1) You can’t replace the trigger guard in New Frontier Lowers (it’s integral to the cast) My opinion of course. After going to the range for the first time I found the lower cracked on both sides of the buffer tube when I got home, it was barely still connected. Think the problem is with individual manufacturers rather than with the polymers. Don’t forget even lightening your rifle has trade offs. For a very understandable discussion of polymer crystallinity, see this Macrogalleria page. Video Explanation. I have a question maybe someone could help me.. Today I bought AR 15 it has a lower polymer receiver. Don't be misled by chemical formulas that depict polymers such as polyethylene as reasonably straight chains of substituted carbon atoms. I’m not looking for a TEOTWAWKI / SHTF situation with something like this, it’s clearly intended to eliminate weight. I have owned a GIN_U_WINE Colt AR-15, which i put thousands of rounds thru before I traded it off. Processors have been extruding filled polymers for many years. These are tools that are designed to be used all day, outdoors and in, whether conditions are subzero or blazing summer sun. The information provided here does not represent the views of Cheaper Than Dirt! If HK, the pioneer of all polymer guns had problems, then there may be problems. I don’t feel comfortable with a plastic, hammer, and disconect. This is a quote from a website that makes carbon fiber parts for building construction: (begin quote), Carbon Fiber vs. Metals The forged still works fine. Being an older fellow, I remember cars with metal dashboards and was so disappointed when they started making them with synthetics (plastics). (More). A friend who is a police officer and former marine armorer showed my how rushed and haphazard assembly can strip even aluminum upper( he fixed a friends DPMS lower by dremeling it out and inserting a threaded washer- you’d never know from the work he did, even though he advised our other friend to just go buy another stripped lower and cannibalize the trigger group from the damaged dpms lower). Tore apart after about 20 rounds, but 20 rounds might make all the difference. It did not become generally useful until the mid-nineteenth century when Charles Goodyear found that heating it with sulfur — a process he called vulcanization — could greatly improve its properties. And, I still have a soft spot for those old forged steel and hardwood battle rifles. I bought a new fronteer poly lower for an AR build for my wife because my rock river arms AR was too heavy for her … With the polymer lower her AR weighs in at 5.5lbs … Works great …holds zero perfect and she can carry it and shoot it all day no problem … I gotta say the lighter weight makes it feel really fast to target..slightly more recoil but who cares its only a .556 right? In fact, taking weight off the lower and upper makes it way less accurate. They have all worked great!! Getting to accuracy there is not a one of them oldies at 300 were designed to group as tight as run of mill ars today. Bakelite is the first synthetic plastic and is known as a “material of thousand uses” due to its versatile applications. A glock is, why would an AR with a polymer lower that operates the same and is ever bit as durable also not be a great gun for when SHTF? Why does a rubber band heat up when it is stretched, and why does it spontaneously snap back? An excellent textbook for non-specialists with some background in chemistry is Giant Molecules: Essential Materials for Everyday Living and Problem Solving by Charles Carraher Jr (Wiley-Interscience 2003; Google Books). This in turn encourages shipment of these wastes to low-wage countries, thus reducing the availability of recycled materials in the countries in which the plastics originated. ... A safety hard hat is much harder than a gel shoe insole, for example. Even if polymer will not last as long as aluminum, it’s still a functional gun–better than none. Other polymers (generally those that are highly cross-linked) do not melt at all; these are known as thermosets. Saying that the up side is long term storage would would be great. If you drop a gun and have to worry about it breaking, then obviously It’s an issue. The threads didn’t seem to be as tight as I think they should be. Everyone wants to buy something “affordable”, but when you have to use the rifle to rapidly get to prone, or buttstroke someone at close quarters the cost of your plastic lower will immedieately be replaced with the thought “am I going to break my gun?”. Bullet-proof vests are one of it more colorful uses, but other applications include boat hulls, drum heads, sports equipment, and as a replacement for asbestos in brake pads. Thin and very strong films of this material are made by drawing out the molten polymer in both directions, thus orienting the molecules into a highly crystalline state that becomes "locked-in" on cooling. All comments are held for moderation and will appear after approval. boy was I surprised. As of right now the only home 3D printed AR-15 receiver I’ve ever seen created lasted exactly 6 shots (the receiver split in half after the sixth). - last modified It turns out, however, that few polymeric substances are uniform in this way.  =  No problems yet, and I don’t expect any. This is especially the case with synthetic polymers, whose molecular weights cover a range of values, as may the sequence, orientation, and connectivity of the individual monomers. Looks awesome with the Rogers SuperStoc. I felt the same way. Until carbon fiber gets to be more commonly used in the barrel and receiver there is not much you can do. I’ll stick with forged aluminum, thank you. If it’s cold enough to make this thing brittle, it will have long ago turned your aluminum or steel lower into a cracker! For instance, a foam-core sandwich has extremely high strength to weight ratio in bending, but not necessarily in compression or crush. Partial photodecomposition, initiated by exposure to sunlight, is a more likely long-term fate for exposed plastics, resulting in tiny broken-up fragments. It is commonly reported to have the highest compressive strength of any unfilled plastic material, and also has the highest tensile strength, highest shear strength, and highest Rockwell hardness rating of any plastic that I have been able to find. I love the concept and think they are a great new product for entry level AR-15 users. They died. 1) The place where the receiver extension (“buffer tube”) connects to the stock is 100% reliable. I treat my guns like all equipment I own- cars, tools, appliances; keep them cleaned, inspected and properly used, and they’ll last. Tires are highly engineered products that use different kinds of rubber in different parts. I communicate with a LOT of other dealers that sell NFA lowers and I haven’t heard of this problem before. please see the Chem1 Virtual Textbook home page. My only suggestion is hardened steel or aluminum inserts for the pins and buffer tube. See here for a more complete definition of the glass transition temperature.