Pennsylvania Game News - August 2022 - 55

often wore out and needed replacing.
Newer ones are designed better and last
far longer, though.
Going forward, it wouldn't surprise
me if regulated guns - only beneficial
in .177 through .25 caliber right now -
undergo further innovation and become
the PCP norm.
PRESSURE EFFECTS
The air pressure in a PCP cylinder
decreases with every shot taken. If that
pressure drops low enough, it will be
insufficient to fire a pellet.
Chances are you'll notice your gun
behaving differently before things get
to that point. As velocity noticeably
decreases, trajectory increases.
This full-to-empty scenario is called
a " pressure curve. " Within that curve
is what's known as the " power curve. "
That's the range - between high pressure
and low - delivering fairly consistent
pellet velocity over a series of shots with
the least amount of velocity variance.
Then there's the " sweet spot, " an even
smaller portion of the power curve. It's
where pellet accuracy is the best within a
certain velocity range. This usually starts
a little below maximum charge.
The .22 caliber Crossman Marauder,
for example, is an unregulated PCP
air gun. It has a pressure range from 0
to 3,000 PSI. Loaded with 14.3-grain
Crossman premium hollow point hunting
pellets, its sweet spot falls between 2,200
and 2,800 PSI.
Charged to that level, it spits out
pellets at 820 to 870 fps. I get half-inch
groups at 30 yards with it for 20 to 25
shots, and 1-inch groups at 50 yards for
about 16 shots.
When the gauge drops to 2,000 PSI,
I typically refill it to 2,800 PSI before
shooting again. That gives me the most
AUGUST 2022
consistent results.
That said, even when pressure drops
to 1,600 PSI, and my velocity falls to
about 760 fps, my groups can still be
decent. But my pellet travels in a steeper
trajectory and hits lower with fewer foot
pounds of energy.
Similarly, the Umarex Gauntlet is a
regulated PCP air gun with a maximum
pressure of 3,000 PSI. In .22 caliber, it
offers consistent PSI output at 900 fps
for 60 shots or so. When air pressures fall
to 1,900 PSI, though, velocity decreases
and trajectory increases, so I fill it back
to 3,000.
In all cases, a chronograph helps to
measure shots, starting from a full air
cylinder. You can use an iPhone app
called " Chrono-Connect " to do the same
thing. If you don't have either of those,
just keep an eye on your shot groups,
noting at what pressures they drop or rise
in elevation.
FINAL THOUGHTS
One more thing to consider is that
some PCP air guns sold in the United
States are actually made in Europe. As
a result, they use a BAR pressure gauge.
It's based on the metric system, rather
than PSI.
Buy one of those and you'll have to
do a little math. One BAR unit equates to
14.5 PSI, so if your gun has a maximum
charge of 241 BAR that equates to about
3,500 PSI.
Now, all that may seem like a lot to
take in. But picking a PCP air gun and
learning to maximize its potential is
really no different than finding the right
combination to get your centerfire guns
shooting as best they can.
Those who take the time to understand
the PCP will find why they are the luxury
cars of hunting air guns.
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Pennsylvania Game News - August 2022

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