Understanding the PS90 and Its Barrel
The PS90 is a unique firearm known for its futuristic design and compactness. Manufactured by FN Herstal, this bullpup-style rifle is chambered in the 5.7x28mm cartridge, offering low recoil and high velocity. Its distinctive features include its lightweight design and top-mounted magazine, which contribute to its compact profile.
The barrel length of a standard PS90 is 16 inches, and the overall length is 26 inches, which keeps it compliant as a standard civilian legal rifle in the United States. However, some enthusiasts may desire a shorter barrel for improved maneuverability, especially in close-quarters situations or for aesthetic preferences.
Legal Considerations
Before undertaking any modifications to a firearm, it's crucial to understand and comply with all relevant laws and regulations. In the United States, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) regulates the possession and modification of firearms, including barrel length restrictions.
Under the National Firearms Act (NFA), rifles with barrels shorter than 16 inches are classified as short-barreled rifles (SBRs) and are subject to strict regulations, including the requirement for a tax stamp and registration with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). Failure to comply with these regulations can result in severe legal consequences.
Research and Plan:
Begin by thoroughly researching the legal requirements and implications of shortening the barrel on your PS90. Ensure that you understand the process before proceeding. For most individuals and gun trusts, a $200 tax stamp from the ATF is required. Additionally, after your Form 1 is approved, you must engrave your name (or trust name), city, and state exactly as listed in Section 3B of your approved Form 1. This engraving must be at least 0.003 inches deep and in a font size no smaller than 1/16 inch. The engraving must be placed in a visible location on the receiver to comply with ATF regulations. Do not install the short barrel or modify your PS90 until you have received your approved Form 1 and tax stamp. Possessing the firearm in an SBR configuration before approval is a violation of federal law.
Apply for a Tax Stamp:
The quickest way to get approval from the ATF is to use their eForms system. You'll need to create an account on the ATF's website eforms.atf.gov and complete ATF Form 1 (5320.1) - Application to Make and Register a Firearm. You could also complete the paper mail-in version of this form, but expect significantly longer wait times doing it this way (some have waited over a year using the snail-mail version). The cost is $200. Fingerprints and passport-style photos are required. Many shops now offer services like the Silencer Shop kiosk, that really streamlines this process. Check the Silencer Shop website and consult with your local qualified FFL/SOT.
There are quite a number of excellent walkthrough videos online about completing ATF Form 1. It is also a good idea to consult with an attorney that specializes in NFA (National Firearms Act). A qualified attorney can provide guidance on completing the form, including what type of applicant is most appropriate for your specific needs, such as individual, trust, corporation, government or other.
Some of the basic information specific to the PS90 SBR Conversion when installing the CMMG 10.4" PS90 barrel on a factory FN PS90 receiver:
- Section 4(a) Name and Address of Original Manufacturer and/or Importer of Firearm (If any): FN Herstal
- Section 4(b) Type of Firearm to be made: Short-Barreled Rifle (SBR)
- Section 4(c) Caliber: 5.7x28mm
- Section 4(d) Model: PS90
- Section 4(e) Barrel Length: 10.4"
- Section 4(f) Overall Length: 20.0"
- Section 4(g) Serial Number: Use the PS90's existing serial number exactly as it appears on the firearm
- Section 4(h) FN PS90 converted to SBR with aftermarket 10.4” barrel and OEM-spec retention system.
- Section 4(i) For all lawful purposes, including personal collection and sporting use.
*The overall length of 20.0" is an approximation and may vary slightly depending on the specific muzzle device used for barrel retention. When submitting your Form 1, ensure that the measurement reflects the firearm’s final configuration, as the ATF expects it to match the approved application as closely as possible.
Replacing the 16" Barrel with a 10.4" Barrel
We recommend using an aftermarket 10.4 inch barrel, like the CMMG 10.4" PS90 barrel whenever possible. While some sources suggest cutting the existing 16-inch barrel, this does not bypass the legal requirement for an approved Form 1. We highly recommend preserving the factory barrel shroud and 16-inch barrel for future use, as factory PS90 barrels are difficult to replace. A 16" PS90 barrel is nearly impossible to find on the aftermarket. Once the barrel is cut, there's no convenient way to restore the PS90 back to its original configuration if needed. Plus, the barrel’s dimensions are critical for proper function. If the barrel is not cut and threaded perfectly, the rifle’s reliability and safety could be compromised.
Once your Form 1 is approved, only the registered owner (whether an individual, trust, or corporation) or an authorized agent may legally assemble the SBR. We recommend using a qualified gunsmith to perform the work.
National Firearm Sales Inc. is not responsible for any damage resulting from this work. This process requires precision, and irreversible damage may occur, including but not limited to damage caused by an extremely tight barrel, misaligned drilling, or metal shavings lodging in the threads while turning the barrel. By proceeding, you assume all risks associated with this modification. No warranty, express or implied, is provided.
Tools Needed:
- Non-Marring Vice
- Masking Tape
- Sharpie
- Measuring Tape
- Measuring Tape
- Drill
- 5/64" Drill Bit
- Hammer
- 1/16" Drift Punch
- Compressed Air
- 15mm Thin Wrench
- Metal Plate (2" x 1-1/4" x 1/8")
- .22-Compatible Cleaning Rod (At Least 20" Long)
The Procedure
Step 1: Drill the hole, then drift out the blind pin from the barrel assembly.
- Use a Sharpie to make two dots 5/8" apart on the masking tape. This will help mark the location of the hole to be drilled.
- Place the punch through one of the markings, then insert it into the existing hole where the blind pin is located.
- Stick the tape to the bottom of the barrel shroud so that the 2nd marking is underneath the shroud.
- Use the marking punch to put a starter dimple in the shroud. This is where the hole will be drilled.
- Use the drill and a 5/64" bit to drill a hole in the new location, starting perpendicular to the shroud, then slowly angling the drill toward the entrance hole of the blind pin.
- Use the 1/16" drift punch and hammer to drive out the blind pin
- Blow compressed air into the new hole to remove any metal shavings and debris that could damage the barrel's threads.
Step 2: Remove the barrel shroud
- insert the metal plate in the flash hider, then lock the muzzle end of the barrel with plate in a vise so that the muzzle device cannot turn.
- Use the 15mm thin wrench on the breech end of the barrel to loosen and remove the barrel. NOTE: the barrel has left hand threads and may be extremely tight. You may need to apply some muscle, and you'll also need to turn the barrel in the opposite direction from normal to remove.
- Once the barrel shroud is removed, ensure that the barrel return spring in front remains in place.
Step 3: Replace the barrel
- With the shroud removed, and the barrel still in the receiver, insert the cleaning rod through the front of the barrel.
- Remove the barrel through the rear of the receiver, keeping the cleaning rod in place to retain all components.
- Slide the new barrel over the cleaning rod, through the rear of the receiver, and through the takedown button, charging spring, charging assembly, and barrel return spring.
Step 4: Install the muzzle device
- Install the muzzle device on the barrel's left hand threads.
- Use the thin 15mm wrench to gently torque the barrel. There is no need for excessive tightening—just snug will do. The left-hand threads make the barrel self-tightening.
- Check for function. Make sure the charging handle assembly operates smoothly and that there is a small amount of front-to-back and rotational play in the barrel. This is necessary for the gun’s delayed blowback system.
Conclusion
Replacing the barrel with a CMMG 10.4" barrel offers a straightforward and reliable method for achieving a shorter barrel length on a PS90. By following the proper procedures and taking necessary precautions, you can safely modify your firearm to suit your preferences while remaining in compliance with the law.
Always prioritize safety and legality when modifying firearms, and seek guidance from experienced professionals or legal experts if you have any questions or concerns. With careful planning and execution, you can successfully customize your PS90 to meet your specific needs and preferences.
This article is intended for informational purposes only and should not be construed as legal advice. Firearm laws and ATF regulations are subject to change. Always verify compliance with federal, state, and local laws before modifying any firearm. Consult an attorney specializing in NFA regulations if you have any legal questions.