by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1

Gamo Whisper Fusion IGT air rifle
Gamo Whisper Fusion IGT air rifle.

Today, we’ll look at the velocity and power of the Gamo Whisper Fusion IGT air rifle. This breakbarrel rifle has a gas spring that seems to intrigue many new airgunners, so let’s talk about that first. A gas spring is a unit that uses compressed gas rather than a coiled steel mainspring to power the piston. Besides that, it’s identical to a conventional spring-piston powerplant.

What’s in a name?
There are many names for the gas spring. Some call it a gas strut, others call it a gas ram, but all these names refer to the same thing. We’re talking about a mechanical device that contains compressed air or other gas (Crosman uses nitrogen — hence Nitro Piston) to push the piston. When the gun is cocked, the piston unit is pushed backwards — making the compressed gas reservoir shorter. When the gas chamber inside the piston becomes smaller, it causes the internal pressure to rise. When the gun fires, this compressed gas pushes the piston forward, and the piston seal compresses the air in front of it.

None of the gas inside the gas spring mechanism escapes. It remains inside, where it can be used again and again. Gas springs are found on modern cars — holding open the heavy back decks and front hoods that used to be held by coiled steel springs. The gas springs on a car usually last for more than a decade, and it isn’t uncommon to find them still working in cars that are 20 years old. Throughout all that time, they’ve been kept fully compressed 99.9999 percent of the time, yet they can still do the job for which they were designed. This is why we say that an airgun with a gas spring can be left cocked for a long time without loss of power.

The advantages of a gas spring in a spring-piston airgun are:
* Can remain compressed a long time without power loss
* Are lighter than powerplants with coiled steel springs
* Vibrate less
* Move faster than coiled steel springs
* Are less sensitive to temperature changes

The disadvantages of a gas spring are:
* Impart a sharp crack to the discharge
* Require nearly full effort even when the piston is all the way forward, making for harder cocking
* Have a sharp recoil that can hurt if the gun is held too tight

Velocity
Now, it’s time to look at the velocity and power of the Whisper Fusion IGT. The first pellet I tried was the JSB Exact RS, a 7.33-grain pellet that’s pretty light for this powerplant. RS pellets averaged 938 f.p.s. after I allowed the rifle a few shots to settle down. The low was 919 f.p.s. and the high was 949 f.p.s., so the spread was 30 f.p.s. I think that will tighten with time and more shots on the powerplant.

At the average velocity, this pellet generates 14.32 foot-pounds at the muzzle. I’d expected more power; but once the gun had settled down, it was fairly consistent at that speed. The RS pellets fit the breech somewhat loosely.

RWS Superdomes
Next, I tried the 8.3-grain RWS Superdome pellet. They averaged 915 f.p.s., with a spread from 909 to 921 f.p.s. The gun is already starting to stabilize.

At the average velocity, this pellet generates 15.43 foot-pounds of energy at the muzzle. Superdomes fit the breech snug but not tight.

H&N Baracuda Match
Then, I tried some H&N Baracuda Match pellets. At 10.65 grains, these were the heaviest pellets I tried. The Whisper Fusion IGT belted them out the spout at an average 824 f.p.s., for a muzzle energy of 16.06 foot-pounds. The spread went from a low of 822 f.p.s. to a high of 828 f.p.s., so the gun was extremely stable with these pellets.

Baracuda Match pellets fit the breech tighter than all other pellets. That tells me the rifle needs something to push against, and deep-seating would not be recommended.

Gamo PBA
The final pellet I tried was the lead-free Gamo Raptor PBA, a 5.4-grain domed pellet. They averaged 1,232 f.p.s. in the rifle, with a range from 1,217 f.p.s. to 1,245 f.p.s. Even with this lightweight pellet, the rifle is still very stable. The total spread is just 28 f.p.s.

At the average velocity, the Raptor PBA pellets produced 18.2 foot-pounds, so the energy is definitely up. But these pellets fit the breech the worst of all those I tested. Some were so loose that they fell out when the barrel was closed, while others fit extremely tight. Because of this, I doubt they’ll give good accuracy.

Cocking effort
The Whisper Fusion IGT cocks differently than any gas spring rifle I have experienced. The initial part of the cocking stroke rises to about 30 lbs. and stays there until the final few inches of the stroke. It increases to 43 lbs. of effort for the last little bit. Most gas springs are consistent throughout their entire cocking stroke, but not the test rifle. It requires two hands for me to cock it more than a handful of times.

Trigger
The trigger-pull seems light and smooth. Of course, we will find out more about that in the accuracy test, but for now it does seem very nice. This is the new Smooth Action Trigger, and it seems to be lightyears better than Gamo sporting triggers of the recent past. I think it’ll be a winner. Stage 1 is short and takes 4 oz., while stage 2 breaks at 3 lbs., 12 oz.

Opinions so far
The rifle has less velocity than the 1,300 f.p.s. Ā advertised, but in this case that’s a good thing. It has exactly what a hunter wants in terms of power. It seems to want to be stable and should not require a lengthy break-in, which is a good thing. Accuracy testing comes next, and we’ll see what it can do in the package Gamo provided. I’ll shoot it with open sights…first at 10 meters, then scoped at 25 yards.