WA GBBs are optimized for HFC134a use. HFC134a exerts less pressure than propane (approximately 70psi vs. 130psi). Use of higher pressure propane can result in the overloading of various parts. The most critically overloaded part is the slide which is difficult to replace. Up until now, upgrading the stock plastic slide to a metal aftermarket slide has been the only way to make WA GBBs reliably survive the increased pressure of propane. Although the aesthetics of a metal slide are certainly appealing, they are very expensive (around $100USD)
The AI Flow Restrictor (FR) is an upgrade part which reduces the force of recoil in otherwise stock WA GBBs. The intent of this product is to retune WA 0.45 GBBs so they recoil with similar properties to a stock WA GBB propelled by HFC134a when they are propelled by higher pressure (and economical) propane. A stock plastic slide can durably perform with propane if the blowback pneumatics are retuned for higher pressure propane (i.e. reduce flow).
1. Will the Flow Restrictor really let me use propane in my Western Arms pistol?
This product has been successfully lifecycle tested in a WA 5” SVI Xcellerator to 20,273 cycles! A machine was built to repetitively fire this GBB under propane propulsion for this test. Propane was supplied through a tube tapped into the magazine. view test footage here.
Life cycle testing apparatus in action
Additionally, the AI FR has been game play tested in:
• Para Ord (non SCW)
• 3.9” Two Tone SVI (non SCW)
• Wilson Combat (SCW)
• 5” SVI Expert (SCW)
• Not recommended for use in fully automatic GBBs e.g. ProKiller series
2. Why use propane instead of what the gun was initially designed for (HFC134a)?
• POWER!: An unupgraded HFC134a propelled WA gun fires 0.2g bbs at approximately 235fps. Propelled by propane, a WA GBB can fire bbs to 320fps! There is no way to achieve similar muzzle velocity in a WA 0.45 GBB with any aftermarket upgrades if HFC134a used as a propellant. Although an unupgraded WA gun can fire propane, it may not do so durably (i.e. slide failure).
• ECONOMY: Propane is quite economical compared to airsoft packaged HFC134a.
• SMELL: HFC134a doesn’t smell strongly enough and you want that smell of death to follow you around when you use propane! AAARRHH!
3. Is it difficult to install?
Not particularly. Airsoft Innovations has produced a comprehensive high resolution instruction video to guide you in the installation of this product. The installation procedure requires basic tools (hex keys, screwdrivers) and can be completed in minutes by those with some mechanical inclination. Those who are not so mechanically inclined can follow along with the installation videos and install the FR in around 10 minutes.
Watch the video and decide for yourself: even if you've never taken down your Western Arms pistol before, the comprehensive instructions should make installation easy. With purchase of a Flow Restrictor, we'll also send you an even higher resolution version on CD, play it back as many times as you like, until you're comfortable performing the modifications. How many other airsoft companies offer you installation videos?
 AI Flow Restrictor Installation Video for Non-SCW Guns requires: Quicktime
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 AI Flow Restrictor Installation Video for SCW Guns requires: Quicktime
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4. Are there any drawbacks?
Yes, although they are relatively minor. As with most airsoft upgrades, there are downsides to improving performance:
• Non reversible installation: In some GBBs, a part has to be trimmed for the FR to work. Because of this part modification, it is not possible to retune your WA GBB for HFC134a use without replacing this part.
• Upgrade hammer spring: In warmer climates, propane exerts a slightly higher pressure. Because of this, stock WA hammer springs sometimes do not strike the firing pin hard enough to completely open the magazine fire valve (this is called light striking). AI recommends replacing the stock hammer spring to a Guarder Upgrade Hammer Spring for reliable hammer strikes.
• Mag rubber shreddies: Stock WA magazine rubber seals (the one at the top of the mag) are not durable with propane use. AI recommends keeping some Guarder Magazine Rubber Seals handy for when your magazine rubber does get damaged. Included with the FR installation video is a guide for replacing magazine rubber seals.
• Incompatible with upgrade metal pistons or recoil springs: The FR is intended to provide recoil similar to stock performance with HFC134a. An upgrade recoil spring increases the forward recoil impact on a stock plastic slide in a way that the FR cannot reduce. Do not use an upgrade recoil spring on a stock slide as there is no data to suggest that a stock slide will not fail in the forward direction with a stiffer spring. The FR is also designed to press into a stock plastic piston. Aftermarket metal pistons are not flexible enough to accept a press fit FR.
5. What if I want to upgrade to a metal slide later?
The modification your perform on your WA to install the Flow Restrictor actually improves performance (by increasing gas flow). This is not safe with a plastic slide (without the Flow Restrictor), but if you choose to upgrade to a metal slide later, simply remove the Flow Restrictor, and you will have more power and more kick, safely handled by your metal slide.
