FRS-15 Stock AR 2015 3-4
Reassemble Buffer Tube

Since I’m stuck on the other side of the country in California, I decided to get my hands on an FRS-15 stock to make my own “non-assault weapon” out of a brand new, left-handed Stag Arms Model 3TL-M in 5.56mm NATO with Magpul’s ACS buttstock and MOE pistol grip. While written instructions came with the FRS-15 stock, I found Thordsen’s web tutorial to be the way to go. Note: A mil-spec or commercial carbine-length buffer tube is required.

Here’s what you’ll need for the installation: Safety glasses to protect your eyes from small flying parts, a towel or small dish for small parts, a stock wrench, two flat screwdrivers, two 1/16-inch Allen wrenches and a Phillips-head screwdriver.


1. Remove Adjustable Stock

FRS-15 Stock AR 2015 lead
Remove Adjustable Stock


  • Move the current adjustable stock to its rearmost position.
  • Use one flat-head screwdriver to slide under the lock-down lever, pressing up to release the pin, and with your other hand and a flat-head screwdriver, pry the pin from under the buttstock.
  • Slide the adjustable buttstock off of the buffer tube.


2. Install Endplate

  • Using a flat screwdriver, press down on the buffer retaining pin to allow the buffer and spring to come out.
  • Using a stock wrench or multi-tool, loosen and unscrew the castle nut enough for the original receiver endplate to slide back about 0.25 inches. Slowly slide the endplate back until most of the tension is off of the rear takedown spring. Carefully turn endplate just enough to expose the spring. Remove the rear takedown spring, detent and pin, and set them aside.
  • Keeping your finger over the retaining pin (it will fly out!), unscrew the buffer tube until the pin is released. Remove the buffer retaining pin and spring and set aside. Completely remove the buffer tube.
  • Now comes the time to remove the receiver endplate and replace it with the shooter-friendly, ergonomic endplate.


3. Reassemble Buffer Tube

  • Thread the buffer tube back onto the lower receiver until it reaches the edge of the retaining pin hole. Insert the spring and retaining pin into the hole, pressing down on the pin while turning the buffer tube about three-quarters of a turn, until it covers the edge of the pin, holding it in place. Make sure the endplate does not cover the hole for the rear takedown spring.
  • Insert the rear takedown pin with the groove facing the rear, drop the detent pin and spring into the hole. Make sure the castle nut is all the way to the rear, slide endplate all the way back, then rotate the assembly over the spring.
  • Press the endplate into its final position against the lower receiver, being careful not to kink the spring. Hold the endplate in place and rotate the castle nut into position. Make sure the rear takedown pin is operating properly. Retighten the castle nut with the stock wrench to approximately 40 inch-pounds. Do not use threadlocker.
  • Slide the buffer and spring back into place and push them over the retaining pin. Rotate the buffer so a round edge, not a flat one, is against the retaining pin.


4. Install THE FRS-15

  • With rifle turned upside down, remove the original pistol grip by unscrewing it from the lower receiver. Note: The safety selector spring is located in between the grip and the receiver.
  • Remove the grip slowly, pulling straight down, not to the side or back, taking care not to kink the spring. Remove the spring, detent and safety selector from the lower receiver and set aside.
  • Remove and discard the shipping support from the end of the FRS-15 stock.
  • Insert the safety selector in the “safe” position and, keeping a finger on it, turn over the receiver and insert the safety detent—with its pointy end down—into its hole.
  • Insert the spring into the right-side top hole of the FRS-15. Slip the stock straight onto the receiver, making sure the selector spring does not kink.
  • Secure the FRS-15 with the Phillips-head screw and washer provided. (Blue Loctite is optional.) Check that the safety selector is operating correctly and there are no gaps between the grip and receiver. If there are gaps, remove it and scrape or file the reinforcing fin inside the grip until you get a good fit.

Note: In order to comply with the New York SAFE ACT, the conversion from a pistol grip to an FRS-15 grip should not be easily reversible. The NYSP recommend that you fill the screw hole at the bottom of the receiver with epoxy, silicone-based caulk or another permanent sealant to demonstrate your intention to not return to using a pistol grip.


5. Install Buffer Tube Cover

  • Remove the buffer tube cover’s shipping support spacer and discard.
  • Slide the tube cover onto the buffer tube. Insert two steel sleeves into holes on the sides of the spacer, and drop it in place with the thin side over the castle nut. The spacer should be parallel with the bottom of the cover. If it is not parallel, file or sand the spacer until you get a good fit.
  • Use one of two 1/16-inch Allen wrenches to hold the sleeve in place while you use the other to install the screws on one side of the cover. Install the screws on the other side. Tighten the screws on each side, using both wrenches, until snug. (Blue Loctite is optional.) Make sure you’re making contact at either the endplate or the castle nut.


Ready To Shoot

How does my new rifle stack up against the law? In California, the FRS-15 stock, when installed on a semi-automatic centerfire rifle with no other restricted features listed in California Penal Code 30515(a)(1)(A-F), does not meet the definition of an “assault weapon” and therefore may be configured with a detachable magazine. Replacing the Stag 3TL-M’s birdcage flash suppressor with a PRI compensator/muzzle brake allowed us to finally remove the “bullet button” and replace it with a standard magazine release.

As for New York, authorities representing the New York State Police and the Attorney General have verbally stated that the FRS-15 rifle stock, when installed on a semi-automatic centerfire rifle with no other restricted features listed in the New York SAFE Act, does not meet the definition of an “assault weapon” and therefore does not require mandatory registration. Please check the letter of the statutes in your state. — Edie King Fasano

Editor’s note: To buy an FRS-15 or stock kits, visit Dark Storm Industries’ DS-15 featureless rifles are semi-automatic with a detachable magazine and include a 10-round Magpul PMAG and are free of the features listed in the NY SAFE Act.



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