TNW FIREARMS HTTP://WWW.TNWFIREARMS.COM/ Gas Piston System (GPS) Installation Instructions Version 1.0 AR 15 Gas piston h t t p : / / w w w. t n w f i r e a r m s. c o m / p r o d u c t s _ p i s t o n _ k i t. s h t m l Inside this issue Parts Inventory 2 Installation Instructions and Troubleshooting 2-7 Finally an affordable Gas Piston retro-fit for your AR15. Our Gas Piston System is easy to install, reliable and performs as well if not better than other, more costly systems on the market. At nearly half the price of other systems our TNW GPS is not only a wise investment but also an investment in time savings. With the system design you will have less carbon build up on your bolt carrier assembly and internal moving parts. Most of the gases never make it to the chamber area to foul your AR15. We express our sincerest thanks for your trust in our product. We welcome suggestions and customer feedback. Best Regards, The TNW Firearms Team TNW Gas Piston System installed on a customer s Rock River Arms Entry Tactical AR15. SAFETY FIRST! Remove the magazine and any ammunition from the weapon before proceeding further. Visually clear the chamber. Place the weapon on safe and re-check to ensure that the weapon is not loaded. Customer installed Manufactured to exacting tolerances Super Customer Support Affordable Reliable TNW has developed a low-pressure, long-stroke gas piston design. Why a long stroke? In order to keep from "hammering" the bolt as the short stroke designs do. We have slowed down the acceleration of the bolt mass and instead accelerated it over a greater distance. The result is less shock forces on the system, longer lasting parts and reliable feeding. It's the difference between unlocking your bolt with a ball peen hammer or accelerating it on a cushion of air!
P A G E 2 G AS P I S T O N S Y S T E M ( G P S ) Inventory This is what your TNW GPS looks like when it arrives at your mailbox. The smaller items are packaged in a clear polymer zip closure bag to prevent loss. Also included is a schematic of the parts using line drawings to assist you with your parts inventory and installation. Please follow all instructions carefully. None of our parts are made to be forced together. If you are meeting resistance during installation- STOP and give us a call or email us for assistance. TIP- Take the time to inventory all parts before starting the There s nothing worse than getting to the end of a project to find something is missing! Step 1 Pull out the rear take-down pin using a nonmarring punch or similar tool. Step 2 Remove the bolt carrier group and using an allen wrench- remove the gas key. 1 2 Step 3 Install the new gas key included with your TNW Gas Piston Kit (fig 3). *Notethe LONG allen screw is made for the slot near the front of the key and the SHORT allen screw is for the rear hole. The front is considered closest to the barrel of the weapon. Apply red Loctite (fig 3A) to the allen screws before tightening. 3 3A
P A G E 3 Step 4 Remove the firing pin retainer from the side of the carrier. Step 5 Remove the firing pin. 4 To Contact Us: PH: 503.429.5001 FX: 503.429.3505 Email: TNWCORP@AOL.com 5 Step 6 Remove the bolt retainer lug. Step 7 Remove the bolt. 6 7 Step 8 Remove the piston rings from the bolt. 8 Step 9 Remove the hand-guards by pulling down on Delta ring and pulling the hand-guard out from the bottom. 9 Step 10 Remove the gas tube retaining pin with a proper sized punch (fig 10). A new pin and gas tube are included in your GPS kit. (fig 10 A) 10 10 A
P A G E 4 Step 11 Remove the gas tube. CAUTION Step 12 Install the newly supplied gas tube-ensure THE HOLE IS FACING DOWN (towards the barrel) before installing the new spring pin. 11 Step 13 Install the newly supplied spring pin. 13 12 Take your time! Our parts are made to fit with little effort. If you are exerting a great deal of pressure on something step back and reassess the situation! Before continuing the installation we recommend performing a test fit without the push rod spring. This is to check if you need to install one of the supplied shims. Not every AR15 is made to the same exacting standard. We hope to alleviate the play resulting from this manufacturing process through the use of shims. See the next page for more... Go to the next page to see if you need the shims prior to continuing final installation!
P A G E 5 Step 14 Special Instructions We are checking to see if you need shims. Install the push rod WITHOUT the spring by gently inserting it into the hole near the Delta ring and into the bolt carrier chamber. It should move freely back and forth. You are loose fitting your cylinder, piston and push rod onto your upper with no spring or spring stand to determine if there is any end play using your carrier with the NEW gas key supplied with the TNW GPS kit. 14 A Assemble the piston and gas cylinder. 14 B Carefully and loosely fit the piston and gas cylinder to the push rod. 14 C Install charging handle, bolt carrier group and slide forward until it seats. Close the upper and push in the retaining pin. 14 D Pull back on the push rod (towards upper receiver) just enough to check for any play (fig14b). Select from the supplied shims the best fit to fill the space (fig 14D). If no space exists then you may not need a shim. We will cover how to take care of a too long TNW GPS later in this document. If you need a shim select it and set it aside for final assembly. 15 Open the upper receiver again and check to see if the bolt carrier is flush with the back of the receiver. *NOTE: If no end play is felt proceed with installation. 15 14 A 14 C Special Note We are here to help! Call or email us with your questions or if you hit a snag. See our contact information on the last page. 14 B 14 D The shim is placed on the end of the push rod where it connects with the gas piston. Special Note Supplied shims If the bolt carrier sticks out too far and there is no end play, do the following: LIGHTLY sand the small end of the cylinder (see fig below) and keep refitting the unit until the carrier and upper are flush as in figure 15. Do a little bit of sanding or filing at a time then re-assemble until the desired fit is obtained. 6
P A G E 6 Back to Final Assembly If you didn't have to install a shim because everything fit well or if you are done with your selection of shims.we are ready for final assembly. Step 16 Install the spring on the push rod and then install the spring stand with larger end touching the spring. Insert the push rod through the old gas tube hole. 16 Step 17 Assemble the gas cylinder and piston and place it onto the top of the push rod (fig 17) This is a good point to see if your barrel diameter will require use of the supplied clamp spacers (fig 17 A). You may have to displace the pushrod slightly to the left or right to get it to align. At this point you will have to align the assembly with the TNW GPS gas tube. While pulling down on the cylinder (towards the receiver) align the cylinder small end with 17 A the gas tube and gently allow it to slide into place. See the photos below. Install clamp under barrel (with spacers as needed). Use red Loctite and securely tighten the allen head screws (fig 17 B). Do not over tighten. You can damage the assembly. Before assembly of the clamps check your barrel diameter to see if you need any of the supplied spacers! 17 A Notice clamp spacers. Take your time! Our parts are made to fit with little effort. If you are exerting a great deal of pressure on something step back and reassess the situation! 17 17 B Once final assembly has been accomplished the end play on the carrier should be less than.010. Have you seen our other products? TNW Firearms Installation Instructions
P A G E 7 Step 18 Final Assembly Re-check all assembled parts for fit and security. Re-install hand guards. You have now completed your installation. Drop us a line and let us know how your system performed. If you like the product please feel free to recommend us to your friends! Take your time! Our parts are made to fit with little effort. If you are exerting a great deal of pressure on something step back and reassess the situation! Some of our customers have modified their rails to fit our TNW GPS NP CONTACT US: TNW Firearms, Inc. P.O. Box 311 Vernonia, Oregon 97064 A few of our other products Phone: 503.429.5001 Fax: 503.429.3505 Email: tnwcorp@aol.com