These Expansion Chambers are unique in the way CO2 is distributed. It enters the bottom chamber and travels through a series of diamond-shaped cones where the liquid and air are mixed evenly, giving a more consistent flow of pressure to the valving of the marker. Unique to its design, the housing works in any position, even if inverted for remote set-up or crawling situations. If excess liquid is pulled through the system due to rapid firing rates, the diamond-shaped cones act as a centrifuge, slinging excess liquid outward to be recycled through the system.
The ACI Sub-Zero 4 Stage Expansion Chamber is newer, so it should be commonly available, both new and used.
I recently installed this on my Piranha STS G2. The expansion chamber works as advertised by keeping liquid CO2 out of the gun. However, just to be safe, if you're shooting CO2, don't point your gun toward the ground. This allows CO2 to flow into the expansion chamber and could cause some serious velocity spikes. Because the chamber provides extra space for CO2 to convert to a gas, it allows for more consistent velocity. Since I've added the chamber, I've noticed that my velocity spikes range about + or - 5 FPS. Before I put it on, they ranged + or - 15 or more FPS.
ACI does not provide instructions for installing the chamber. It's obvious that it screws into the vertical ASA, but there should be something to explain how to loosen the chamber housing. You have to do this in order to properly run a bottom line to it. As explained in an earlier review, an allen screw at the bottom of the chamber has to be loosened. I had to call ACI and get one of their reps to tell me how to do it. Then, after he explained it, I slapped myself because it was so easy.
I got the chamber for about $40. It was the best price on the Internet. As stated above, it works just like advertised. If you shoot CO2, this is a good upgrade, especially if you don't plan on changing to an HPA tank or converting to low pressure.
9 out of 10
Last edited on Saturday, January 29th, 2005 at 7:33 am PST
As advertised, the product provides for good cold weather performance. I have played with a foot of snow on the ground and more coming down and had no problems with velocity. And, of course, it makes for a nice foregrip.
Installation is not explained well. I have noticed other reviewers mention that when they installed it, the feed came out the side rather than the back. This is not the product's fault. This is the documentation's fault. When properly installed, the feed *will* come out the back.
[On the bottom of the chamber there is an allen head screw. After screwing the chamber tightly into the gun, loosen that screw and twist the chamber until the feed is coming out the direction you want it to come out. Tighten the screw again. Voila!]
It does what ACI says it will do. The cost is agreeable. A good deal for folks like me who live in areas where they may want to play in the cold but do not have access to HPA fills.
I recently installed this X chamber with a new bottomline configuration on my standard Rebel.The first time I ever used it was in 45/50 degree weather.And I will never go back to a vertical configuration!My shots stayed perfectly at 290 fps the whole time; never jumping more than 5 fps!Very impressive for ANY expansion chamber.I had no problems with Co2 what so ever.I have never seen any gun NOT leak the first time you install a bottomline or and X chamber.I didn't have to make any adjustments!I also gained a good many shots per tank with it.Plus the colors rock and it makes a kick @SS foregrip.
The only problem you might have is if you have big hands, or like to have plenty of grip room.When I screwed my chamber in the whole way, the input for bottomline was NOT on the back like it should be.Instead it was on the side, so it gets in the way and eliminates an inch or two of grip room.
The cost was killer I've seen many 4 stages in action, and none of them can compete with ACI's.Not even 32 Degrees!If you don't want to waste money on a 6 stage, then this is the best alternative!
9 out of 10
Last edited on Saturday, January 29th, 2005 at 7:49 am PST
This thing is awsome. It gives you consistant shots in cold weather. I have one and use it with my Inferno Heat, which is a great marker. Another good thing about the expansion chamber is that it comes in red, blue, or black, so you can get to match your gear. I like the design of the sub-zero 4 stage better than any other chamber. The price is good too, at 35 bucks. If you use co2 and play in cold weather this thing is a must. It is also very comfortable for a grip.
Could be cheaper, but i can't complain. It would be cool if there was more of a variety of colors.
This is a great add on for any gun that runs on co2. If you have problems w/ your gun in cold weather this is for you.
I have a Piranha G2 VTL onto which I attached this unit and a bottom line configuration. The Chamber works as advertised - Prevents liquid CO2 from getting into your valve system. It looks good and operates well. I got the 4-stage instead of the 6-stage because of a)price, b)I didn't want too long a foregrip. The construction is simple and it uses vaseline instead of normal gun lube (as per the ACI tech).
Took me awihle to get used to using this device. The trick is, to reduce the amount of liquid CO2 that gets pushed into the unit when you first install the CO2 tank you should install by holding Tank (& gun) pointing up so that only CO2 gas enters the unit (I guess this is common sense, but.......). Since the chamber is empty upon first tank installation, the CO2 will push into the unit until pressure equalizes. If you hold the tank horizontally, it's the liquid form that gets pushed into the chamber. Since it can hold quite a bit of liquid, you will shoot liquid CO2 into your marker for some amount of time.
Note: I did not get any paperwork with this unit when I purchased it from the store.
I would recommend this unit to anyone who's not using an anti-sipon tube. It may be a more expensive way to solve the liquid CO2 problem ($10 vs $30), but it does make the marker look better and provides a good foregrip to improve overall handling. You can also switch tanks with friends even though they don't have the anti-siphon tube built-in. The unit is hefty and serves as a good counter balance for my 12oz tank. Now my Piranha's balance point is right at the rear of the handle. I like it. I also found that the 4-stage works well enough for me. I normally shoot in 68-85 degree weather.
It Keeps liquid CO2 out of the Gun. this in turn means
longer lasting o-rings in the gun more consistant
velocities since you're running on the air. No shoot down in velocity during Rapid firing..... It is also more compact then the 6 stage and it stills makes a kick ass fore-grip.
If u live in colder weather this is a must!!!!!!!!
If you need a fore grip just spend the extra cash to get an
EX-chamber instead of buying a useless gas-thru grip
****EX-CHAMBERS ARE NOT NEEDED IF YOU ARE RUNNING