Frequently Asked Questions


1. Will aftermarket hand guards fit my OPS-416 Piston Kit?

You will need at least 1 7/8” ID clearance for the piston chamber to seat properly.

FAQ Hand Rail.png

Here are a few aftermarket hand guards that work well with our kit:

Manufacturer                        Model                  Type                                  Comments                                                           

Black Dawn Industries         MFRC                 1 Piece Free Float              Requires the removal of Delta Ring

Black Dawn Industries         MMR                   1 Piece Free Float              Requires the removal of Delta Ring

Seekings Precision              MCSR V2        1 Piece Free Float               Requires modified Op-Rod

Lancer Systems                   LCR                       1 Piece Free Float               Requires the removal of Delta

Lancer Systems                   LCH5                     1 Piece Free Float              Requires the removal of Delta

Spikes Tactical                   LW-BAR                 1 Piece Free Float              Requires the removal of Delta

Guntec USA                        GT1326-10              1 Piece Free Float             Requires the removal of Delta

Aero Precision                APPG400001          1 Piece Free Float             Requires the removal of Delta 

Aero Precision                APPG400002          1 Piece Free Float             Requires the removal of Delta 

2. How do different barrel nuts affect the Osprey Defense kit? 

Regular Barrel Nut: A standard barrel nut is 1 1/4” long. Our piston system operates with no issues.

Regular Barrel Nut: A standard barrel nut is 1 1/4” long. Our piston system operates with no issues.

Free Floating Hand Guard Barrel Nut: Typically 1 3/8“ in length. For these you will need our Modified Op-Rod, which you can choose when purchasing.

Free Floating Hand Guard Barrel Nut: Typically 1 3/8“ in length. For these you will need our Modified Op-Rod, which you can choose when purchasing.

Two-Piece Free-Floating Hand Guard Barrel Nut:  Open End: This type of barrel nut exposes the gas tube when installing. This is also 1 3/8” and you will need to install a Modified Op-Rod.

Two-Piece Free-Floating Hand Guard Barrel Nut:  Open End: This type of barrel nut exposes the gas tube when installing. This is also 1 3/8” and you will need to install a Modified Op-Rod.

3. What exactly is the difference between the various op-rod choices?

  • The 16” Carbine (See photo below) is now the workhorse of the AR-15 community. The op-rod on the bottom is a regular Carbine-length, which measures 6 3/8”. The modified carbine op-rod is exactly the same length, but the shaft (the black portion) is 2 5/16” long while the regular Carbine shaft is 2 25/32”. The modified rod allows for more travel when using a free-floating hand guard’s wider barrel nut.
  • The 18” Mid-Length op-rods measure 8 3/8” total. The black shroud on the modified measures 4 11/32” while the regular measures 4 25/32”.
  • The 20” Rifle-length op-rods (not pictured) measure 11 3/4” in total length. The black shroud on the modified op-rod measures 7 11/16” while the regular measures 8 5/32”.

4. What Calibers will the OPS-416 work with no Issues?

*A standard 3oz buffer from www.brownells.com will work with all calibers.

*Note: Do not use a gas block with an adjustment. They lose too much gas.

5. Will my OPS-416 fire in full-auto if I possess a transferable M-4 or post-sample?

Absolutely. Our kit has a high and low-range built into the gas port in the spigot meaning no gas regulators or valves are needed to adjust the flow of gas to the piston chamber.

6. Will we be offering a 308 Kit?

We are now in the developmental stages of the 308 and we can assure you it will be worth the wait.

I hope this was helpful, but if you have any other questions, please contact us at info@arkdefense.com