Poly Receivers Testing: Prologue

It’s been on the to-do list for a long time, but I’m finally able to give some apples to apples comparisons between the New Frontier Armory LW-15 polymer lower and the TN Arms hybrid lower.  Before we get to the thorough run-down with tons of photos I wanted to do a quick first impressions post.

New Frontier LW-15

New Frontier Armory brought their polymer lowers to the market a year or so ago, and the lower I have on hand is from the first batch originally released back then.  It’s been a long wait to find other polymer lowers that hold up to real use, meaning not .22 grade and able to withstand a beating.  We’ve seen plenty of other lowers fail miserably at the buffer tube tower, pistol grips break off, bolt catch pin shoulders crack or takedown pin shoulders fail, but New Frontier spearheaded development of a lower with tougher polymer more akin to a pistol frame than the airsoft grade junk some others have used in the past.

The LW-15 comes to market at $120 (plus shipping and transfer) as a complete lower ready to use.  Like most complete units it has a basic M4 style stock and A2 style pistol grip, both of which I absolutely loathe and would immediately replace.  The bulk of the LPK is polymer, including poly takedown pins, detents and a 100% polymer fire control pack (sans springs of course) that works shockingly well in my experience.  New Frontier sells these LPKs for $35 plus shipping direct from their website.


  • Excellent fit and finish
  • Strong polymer blend reminiscent of a modern handgun frame
  • Bundled polymer LPK is surprisingly nice with minimal creep and fairly light pull
  • Weighs just over five ounces stripped
  • Overall weight complete is just over 7oz lighter than an aluminum lower


  • Not sold stripped or without the stock kit, nor as a pistol config
  • Buffer threads aluminum to plastic, pistol grip screw threads steel into plastic
  • Straight/flat style trigger guard, permanent
  • SAFE/FIRE only, no pictograms
  • Polymer LPK detents are easily broken


TN Arms Hybrid

Tennessee Arms is a newcomer to polymer receivers, but went all out designing a hybrid receiver intended to fix some of the deficiencies of prior poly lowers.  Along with changing the composition of polymer to a glass-filled nylon type very reminiscent of quality rifle stocks, TN Arms molded in threaded bushings for the buffer tube and pistol grip screw to alleviate metal to plastic thread issues.  They’re a very small outfit and have run into numerous hurdles with the lowers throughout development, but have been busting hump fixing and tweaking the molding process continually improving the production cycle.

The TN Arms stripped receivers come to market at $55 plus shipping and transfer direct from their website, with the plain black lower currently on sale for $45.  They offer a multitude of colors as well as complete assemblies using color-matched furniture.  TN Arms supplies standard mil-spec type steel LPKs with their complete kits.


  • Extremely sturdy polymer blend, even compared to the LW-15
  • Extra reinforced buffer tube area to complement the bushing
  • Brass bushings for buffer and grip screw threads, the claim to fame
  • Brass bushing for buffer tube is EXTREMELY strong!
  • Minimal increase in weight over the all-polymer LW-15 (~0.5 oz)
  • Rounded, enlarged trigger guard
  • Sold in various colors including FDE, OD green, foliage green and pink


  • Fit and finish is lacking, including out of spec (width) grip screw area, mold defects and rough lines
  • Type of polymer gives an admittedly ugly surface finish
  • Chintzy Safe/Fire markings even uglier than the LW-15


Testing Plans

Going forward I’ll be using identical New Frontier all-polymer parts kits in both lowers, which I’ve tested to some degree in a TN Arms lower already.  It works, though I have some concerns about the polymer takedown pins.  Once each lower is put together with matching parts kits, a basic M4 stock and whatever spare grips I have laying around I intend to do a lot of bashing and thrashing to see how the buffer tube area holds up.

Historically, where the buffer tube threads into the lower breaks spectacularly, while the bolt stop pin area and front pivot pin area are prone to cracking.  Once I have an upper assembled to work with, I will induce stuck cases and “mortar” both lowers repeatedly as a practical field test of this failure-prone area.  Both companies offer warranties that appear to cover such breakage should it occur, so we’ll see what happens!