| PCRI Product
Evaluation
Cyclone On/Off Valve for the Automag
The Cyclone On/Off Top is manufactured by
Leads Metal Products Inc. The Cyclone
On/Off Top is designed to reduce velocity drop-off with your Automag. Anyone
who has ever used an Airgun Designs' 68 Automag
for any extended period of time has almost certainly experienced velocity
drop-off problems during rapid fire. Drop-off (also known as shoot-down and
walk-back) is the condition where, under rapid fire, the gun starts to lose
velocity after a number of shots. This occurs when the air chamber behind
the bolt is not completely filled to regulated pressure between shots so
subsequent shots are fired at low pressure, and therefore come out with low
velocity.
The reason this happens is because of restrictions in the gas-path through
the Automag. The single most significant bottle-neck in the gas-path is the
on/off valve. This valve lies immediately upstream of, and directs the gas
flow to, the air chamber. The gas-path through the on/off runs through a
part called the on/off top, a brass piece that fills most of the valve space
and is supposed to direct the gas flow to the air chamber. The problem is
that this part offers very little space for air to flow through it, and therefore
significantly restricts the flow of gas through it. Another problem is that
the valve bottom partially occludes the hole leading forward to the air chamber.
The Cyclone is a replacement on/off valve top which is designed to correct
this problem by offering a larger gas path through the on/off.
Design/Construction
The Cyclone was designed as a replacement for the on/off valve top only.
The stock valve bottom, piston, and seals are used throughout the rest of
the on/off assembly. It is machined entirely from stainless steel and is
nothing more than a thin disc at the top and bottom connected by two slim
posts to space them apart. Large holes are drilled in the discs to allow
passage of the on/off pin and to ensure free flow of air into the valve.
The rest of the Cyclone is simple empty space.
The Cyclone leaves mostly empty space in the on/off top area so as to provide
an extremely low resistance path to the air chamber. We also like the
use of stainless steel with something that really has so little material
holding it together. On the other hand, the Cyclone is only a valve top
replacement and therefore does not address the problem with the stock valve
bottom which still partially occludes the hole leading to the air chamber.
As such, the Cyclone is a decent design which takes the opening of air-flow
space in the valve top to an extreme. On the other hand, it doesn't really
break any new ground or address any of the other failings of the stock on/off
design.
Design/Construction rating [3]
Performance/Versatility
In testing the Cyclone I addressed the two biggest reasons that people experience
drop-off. The first is restriction of air flow through the on/off valve during
rapid fire. The second, and probably most common, reason for drop-off is
short-stroking. Short-stroking results from a person "riding" the trigger.
We used an Auto-Response trigger to test the flow-rate characteristics of
the Cyclone. The Auto-Response is a complete grip-frame and trigger mechanism
replacement which allows a 'Mag to shoot on both the pull and release of
the trigger. This has two advantages. First, it allowed us to shoot very
fast. Second, it forced the user to cycle the trigger completely so we knew
that any drop-off was not the result of short-stroking. We used a 68 Micromag
equipped with an Auto-Response and the Cyclone.
As with the stock valve and other modified on/off tops, the Cyclone did not
fare particularly well. After a few shots, the velocity rapidly dropped off
and the gun hung up and stopped functioning entirely. Since the only valves
that have successfully passed this test have been complete on/off replacements,
we can only conclude that there is a flaw in the stock valve design that
mere on/off top replacement can not alleviate.
To test how the Cyclone handled short-stroking, we fired the gun over the
chrono without completely releasing the trigger between shots (I intentionally
severely short-stroked the trigger). It is in this area that the Cyclone
impressed us. Where the stock valve allowed velocity drops of about 50-60
fps when short stroked, the Cyclone only allowed velocity dips in the 20-30
fps range. This is a significant improvement over the stock, and quite a
bit better than any other valve I've tried.
Performance/Versatility rating [3]
Warranty/Price
At an MSRP of $19.95, the Cyclone is almost double the price of most on/off
top replacements. This is a lot of money for such a tiny piece of metal.
The AKA's warranty protects you against manufacturing defects, which is really
all you'd worry about with as simple a part as this anyhow.
Warranty/Price rating [2]
PCRI IS PLEASED TO AWARD THE CYCLONE ON/OFF TOP OUR THREE STAR SEAL OF
QUALITY. |
