Last year, I was poking around on a high traffic firearms site when a company rep came on asking members for volunteers to run a polymer lower through it's paces. I contacted the rep by PM and told them I'd be willing to buy one and run it as hard as I would a forged aluminum receiver and would report the results honestly. The rep got back to other members who volunteered but my request was ignored and I griped about it here on m4carbine.net. Brian at US Arms saw my complaint and contacted me to ask if I'd like to evaluate their new plymer lower. He said I was welcome run it hard and report the results- warts and all. Though skeptical about plastic lowers, I agreed to give them a fair shake. http://usarmsllc.com/Patriot-15.html
I expected a stripped lower, but they sent me one that was complete. Everything is polymer except the FCG, pins, springs, castlenut and end plate and buffer. That's right, the FCG is metal, including the hammer. The receiver extension is also polymer and is molded to the commercial pattern. I think US Arms would do better if they used the mil-spec dimensions.
The receiver seems stiffer than other polymer lowers I've looked at. The fence on the right side that runs from the front receiver pin to the mag release has been made thicker for added strength and rigidity. There is also a fence running around the mouth of the mag well which is flared without being too big. The lower comes with an integral trigger guard which has a large opening. Stock is of the M4 style and has a surdy polymer sling loop. The RE has six positions. Buffer has no markings so I assume it's carbine weight. I assume the action spring is of the standard variety.
Standard AR triggers run from atrocious to decent. This trigger has the usual gritty creep, is a little on the heavy side but has a surprisingly crisp break. I haven't taken the time to pull the FCG out and grease it up but I think it will be fairly nice once I do. As tested, MSRP for a complete lower is $199. It's $89 for a stripped lower. PSA is offering a complete polymer lower for $129
I borrowed a 16" upper from a PSA carbine to test this lower with. The receiver pins are a little stiff and need a tool to push open. Fit around the back of the upper is a little off. There is a small gap at the curve but where it's vertical, it fits a bit snug. The good news is that for those who worry about such things, there's no rattle!
The complete lower M4 style stock weighs in at 1 lbs, 12 oz. In comparison, a PSA lower with a S&W made M4 stock weighs in at 2 lbs, a weight savings of a quarter pound. A PSA upper with an Aimpoint H1 Micro, Surefire x300 weapon light, Mossie Tactical light rail and round mid-length handguards was used to test the US Arms polymer lower. The whole package weighed in at 6 lbs, 11 oz. The same upper on a PSA lower with M4 stock weighted in at 6 lbs, 15 oz.
There was a little binding towards the end of the travel when cycling the action. A couple rounds of 55 gr American Eagle did not completely go into battery during firing. However, after I added a few drops of oil to the BCG and the problem went away. Maybe it was the drag, maybe it was a dry BCG, maybe a combination of both. Because of the weather, I was only able to fire one mag. What first struck me was the carbine felt lighter and livelier even with the weight shifting towards the muzzle. I still dislike the duckbill of the A2 pistol grip and don't like black furniture. I didn't notice the M4 stock being uncomfortable compared to the Magpul CTR but a longer shooting session might change that impression.
The receiver has clean edges and corners and is without distortion. The surface has a matte finish that matches the PSA upper well. There is more flash at the mold line than there should be and the only mag that drops free is the Lancer L5. Magpuls, Troys and GI mags need to be stripped out. There is more stiction than usual between the stock and RE but nothing to preven the shooter from easily making adjustments.
I contacted Brian at US Arms about my concerns. He said they are tightening up QC and expressed concern the flash and tight mag well made it past QA. He also told me I could return it so they could address the problems. He's dedicated to making this right.
A few other items of note: Adjusting the windage and elevation of an Aimpoint Micro in a cold rain is very awkward. Removing the small caps with stiff hands was difficult and I worried I'd drop the cap and lose it.
The plastic of the IO cover is stiffer when it's cold. When I popped the caps off the lenses, they didn't flip out of the way. I had to snap the covers together to see through the sight. The caps did an excellent job of keeping the rain off when snapped closed over the lenses
Every rifle should have a sling.
Hats with full brims rock. Never leave home without your jacket.
In full disclosure, I did not buy this lower. US Arms sent it to me (via a local FFL, Quantum Guns in Spanish Fork Utah) without charge, for evaluation. Other than them sending me this lower, I have no other connections with the company, financially or otherwise.
As weather and time permits, I'll continue putting this lower through it's paces. I won't baby it, but I'm not gonna set out to see how much it'll take before it breaks. It's advantages over other polymer lowers is increased stiffeness and a metal LPK. It's advantage over an aluminum lower is a weight savings of a quarter of a pound. MSRP is higher than than some other polymer lowers, but street pricing should make them more competitive. Whether or not they prove to be durable enough, only tine will tell. I'll give updates with my findings
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