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Scoring a bull’s-eye with easier processing

LWRC International worked with PolyOne to cut cycle times and avoid costly oil-cooled molds with a specialty thermoplastic material


The Challenge

How did an arms manufacturer find an alternative material for Picatinny rail skins that could accelerate processing, reduce costs and eliminate painting – all while delivering top performance?   

By setting its sights higher

In the past decade, high-performance plastics have become the standard for pistol frames. Today, the use of plastics has expanded into rifle components such as grips, stocks and magazines. One important application is rifle rail skins. These molded plastic coverings supply impact protection for the rifle rail – a slotted bracket featuring locking devices used to attach accessories such as tactical lights, laser aiming modules, night vision devices, reflex sights and bayonets. The rail skin also shields the user’s hand from heat. Materials used for rail skins have to be heat resistant and tough at both ends of the temperature spectrum.

Arms manufacturer LWRC International, LLC, had been using polyphthalamide (PPA) to mold Picatinny rail skins for its M4 semi-automatic rifle. While PPA delivers high heat resistance, processing involves long cycle times and oil-cooled molds that require extended setup and are expensive to operate. When LWRC designers decided to modernize the M4 rifle by updating its look and feel and enhancing the operating system, they also looked for a new rail skin material that could withstand heat, cold and abuse like PPA, yet process more easily and cost-effectively.

A superior replacement could help LWRC cut costs and, just as important, give its designers greater freedom to make the updated rifle more appealing to customers. So the company was under pressure to find the ideal material. 

The Solution

For expert assistance with this challenge, LWRC called on PolyOne. Impressed by the PolyOne team’s extensive knowledge of rail skin requirements and its processing operations, LWRC accepted their recommendation to use a specially formulated Edgetek™ polyamide in black and flat dark earth colors. This high-performance thermoplastic delivered the necessary heat, impact and abrasion resistance, and could be molded in traditional water-cooled tools, making it significantly easier to process than PPA. Also, the pre-colored material eliminated the need for painting. PolyOne supplied technical support to optimize the existing tool for the Edgetek formulation and participated in molding trials. 

Taking advantage of Edgetek’s improved processability, LWRC designers engineered a molded-in, polymeric locking device rather than fabricating, heat-treating and plating a separate spring steel clip locking mechanism. This new locking device cut costs significantly and enabled the rail skins to be used on Picatinny rails from any manufacturer, making it easier for consumers to customize their rifles.

The Impact

LWRC accomplished all of its objectives with PolyOne’s advanced Edgetek technology: cycle time reduction and cost savings; and, as an added bonus, they were able to enhance the design with a molded-in locking device. 

  • Faster cycle times = higher productivity:  LWRC streamlined cycle times by 13 percent as a result of processing enhancements, including switching to an efficient, water-cooled tool and eliminating secondary painting. 
  • Cost savings = $30,000 annually:  The company saved almost $15,000 in material costs in the first year and an additional $3,000 because polyamide has a lower specific gravity than PPA. Other savings came from a reduced scrap rate and higher productivity. By expanding the use of Edgetek technology to additional applications, LWRC estimates savings will grow to $300,000 annually.
  • Improved processing = design innovation:  Better processability allowed LWRC designers to engineer a molded-in locking device that enhances and expands usability of the rail skins. 
  • High performance = customer peace of mind:  With tough, heat- and impact-resistant rail skins, LWRC enhanced its reputation for rifles that perform reliably under demanding conditions. 

“Our military troops and law enforcement officers put their lives on the line every day in extreme conditions and circumstances in service of our country and communities,” said Darren Mellors, LWRC executive vice president. “We feel they entrust us to produce products that are tough enough to withstand any situation, so that they don’t need to think twice about whether the product will perform as designed. Thanks to PolyOne, our products are just as tough as the men and women who carry them into harm’s way.” 

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