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RA-Tech NPAS For GHK AK GBB Review

OptimusPrime

Commie Bear Airsoft RA-Tech NPAS For GHK AK GBB Review

Commiebear Airsoft does a quick review of the RA-Tech GHK AK NPAS which is a recommended upgrade to GHK AK GBB owners... "Quick review on the AK NPAS:

  • Type I - Nozzle only. Type II - Simple adjustment key. Type III - Jointed adjustment key
  • Absolutely get at least one Type III nozzle with the ball joint adjustment key. The Type II can only adjust the NPAS when field stripped.
  • NPAS clicks are very tactile and audible
  • The supplied o-ring is slightly oversized, but I suspect it accounts for the o-ring contracting when cooling down
  • RA-tech has done away with the redundant secondary o-ring
  • The perforations on the piston face are enlarged ensuring a more stable expansion of the o-ring when cycling
  • NPAS adjustment is unfortunately not linear under 1.35J. Between 1.35J and 1.56J I've had at least 12 increments available, while the power drops an entire 0.1J per increment after that threshold. This is probably a limitation with the platform's gas system
  • Power however is very stable, tested with 12kg RWA gas at 20C, 0.28g, ~210mm A+ hop&barrel group. Maximum power is 1.6J, goes all the way under to 0.9J and lower

Clarifications:

  • I keep referring to the BCG cylinder wrong, the o-ring is mounted on the nozzle which expands against the BCG cylinder walls to create a seal as the gas flows into those perforations
  • The NPAS adjusts the length of the nozzle VALVE to delay or expedite the gas cutoff
  • With reference to the 74U length GHK AKs, the platform is pretty inefficient due to the short inner barrel length when using loading anything lighter than 0.25g. The difficulty in tuning the short AKs to 1.2J lies in the fact that the 1J nozzle always outputs less than 1J with the 74U, while the 1.5J nozzle's power fluctuates alot unless you use 0.28g and above. My 74U shoots 1.3J/0.28g stable with the 1.5J nozzle but as stated this is sitting on the CQB limit, while loading 0.25g/1.2J is not a stable configuration.

Notes:

  • Clockwise turns contract the nozzle valve to delay the cutoff.
  • Counterclockwise turns to extend the nozzle valve to cutoff early.
  • Nozzle return spring mod will not be possible with this nozzle as there isn't any point to anchor the spring to, nor was this nozzle designed to be disassembled
  • The pin in the nozzle is a small hollow 1mm pin, I don't think most owners will have the right punch to remove this

PSA:

  • The nozzle sits very tight with 0 vertical play when completely retracted. Receivers with a slightly misaligned feed ramp or a BCG with tighter tolerances will not be able to go into battery"

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