Hpa has evolved and is quickly becoming a readily available option for airsofters. HPA airsoft guns are generally known for the long hose running from the rear to an external tank. This can prove to be problematic for those who wish to put down their primary rifle or the potential chance of the line getting snagged on something or breaking the emersion for some. The nature of the hose line has been a drawback for me to adopt an HPA system but this build for a fellow player may have just changed the game for me.

Redline Airsoft created this wonderful little engine called the N7, combined with the mechanical trigger and the Airstock it has reduced the HPA profile to being a self-contained unit. Finally! An HPA system that doesn’t require a hose. This proves to be a lighter and better solution and the next evolution of HPA systems… Hopefully.

Installing this HPA engine can prove to be time-consuming it isn’t “Rocket Science”
But you will need some tools to do so, I would recommend if you have little to no experience you get a proper airsoft tech to do the work.

To begin installation you will need to strip the of the gearbox.
Once you’ve gutted 97% of the gearbox leaving the trigger, tappet plate, and safety arm, the N7 can simply drop in along with the trigger group. Redline has two options: the electronic trigger group allowing you to utilize regular fire select options and the mechanical option. The mechanical trigger is easier to install and ultimately limits your gun to semi-auto only! The trigger system is adjustable, so you can finetune the pull to your liking and to my surprise it was next to impossible to trip up while spamming it. Luckily Redline provides a detailed  manual to guide you step by step on the installation.

There is however, a recommendation to cut the rear of the gearbox off for easy maintenance, I did this to the rear of the E&C gearbox shell with a dremel, it took quite a few a hours and some TLC to get it just right. Unless you have the time, tools, and knowledge it is NOT easy. The manual selection is under the Airstock page here.


For installing the Airstock Gen II you will need to do a little bit more work. The buffer tube needs to be cut to 8mm exactly to accommodate for the butt plate and regulator that attaches to the lower receiver. The installation onto the E&C 416 I was provided with required some modification as it is a clone of the VFC and not entirely exact, nothing a Dremel and a file couldn’t fix though! With the butt plate on the rear and the airline running through the stock, you can use the small tool provided to cut the air hose to the exact size for the regulator. Be sure to apply some lubricant before connecting the regulator. The regulator can be adjusted using an alan key on the rear allowing you to increase or decrease the volume of air. It also allows for a tournament lock! The manual can be found on the Airstock page too.

If you happen to go down the route of the Airstock system you are now entering the world of hoseless HPA builds. In my opinion this is superior in nature because the whole package is self-contained and restricted to the gun. Out of each tank you get a minimum of 900 shots. If you are wise with your shooting this could last you the entire day. This gives the player more room to maneuver, breaking you free from having to disconnect and reconnect constantly. Shooting wise, the gun was shockingly quiet with the suppressor on the end as the system is closed bolt and pre-pressurized. Keep in mind once you’ve disconnected the air-tack that the N7 is still pressurized! Before you pack your gun away be sure to discharge the remaining air as it could be a concern for safety outside of the field of play.

Overall I was amazed at the performance of this HPA engine. Not only in its simplicity and cost effective nature, but in the matter that the N7 performs admirably!

– Schoolboy out