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22 November, 2013

Stoeger ATAC Muzzle Velocity Test Results. Surprise!

Like many people, I’m very dubious about some of the claims for muzzle velocity made by manufacturers for their air rifles. Somehow, these numbers are incredibly high and are not easy to reconcile with the “real world” test results we obtain when making Archer Airguns Gold Service tests on individual customers’ air rifles.

For example, the Stoeger ATAC has these claims for muzzle velocity, in .177 caliber:

“Up to 1200 fps with alloy”.

“Up to 1000 fps with lead”.

Yet in our Gold Service testing, we see muzzle velocities for the ATAC of between about 880 and 940 fps in .177 caliber. What’s going on?

In an attempt to answer this question, Paul and I conducted an experiment here at Archer Airguns.

We took one .177 caliber ATAC at random from stock and fired enough shots through it to burn of the effects of dieseling. We then took 9 different types of pellets, each of differing weights, and fired 5 shots with each pellet type through the same gun in succession across the Chrony.

The average muzzle velocities for each pellet type were then plotted in the graphs you see here.

The results surprised me! The ATAC does actually achieve - and even exceed - Stoeger Airguns’ claims for muzzle velocity. But it all depends on what pellets you use!

Here’s the data Paul and I gathered. (Click to enlarge the data and graphs).

Plotting the average muzzle velocities against pellet weight gives a graph looking like this.

As you can see, the muzzle velocity falls with pellet weight. Duuhhhhh..... Of course this is not very surprising, there’s only so much air in the compression chamber of the gun and heavier pellets will need more “push” to fire than lighter ones.

It’s immediately obvious that this ATAC - chosen at random - meets, or even exceeds, Stoeger Airguns’ claims for muzzle velocity.

With the lightest alloy pellets tested - 5 Grain Gamo Raptors - the muzzle velocity was 1242 fps. That exceeds the manufacturer’s claim of “up to 1200 fps with alloy”.

Testing with the lightest lead pellets - 7 Grain RWS Hobbys - gave a muzzle velocity of 1002 fps. That meets the claim of “up to 1000 fps with lead” right on the nose.

When the same gun is shot with 8.64 grain Stoeger X-Field pellets - the pellets we use for Gold Service testing - it achieves 916fps. That’s right in the 880 - 940 fps spread we find for these guns in Gold Service tests in .177 caliber.

So, this gun chosen at random gives very representative results for muzzle velocity from the ATAC. The Gold Service muzzle velocities we see with Stoeger X-Field pellets (880 to 940 fps) represent the muzzle velocity tested in this gun with a spread of just +2.5% (940 fps) to -5% (880 fps). I’d say that this is a very respectable performance given that we are always testing new guns that have not yet had time to "settle down" with use.

Interestingly, the ATAC gives a reasonably uniform level of muzzle energy - in the 15.5 to 17 ft/lbs range with any tested pellet, as is shown by the data and the following graph. (This is not always the case with other air rifles we've tested).

Now, this was a muzzle velocity test only. An accuracy test would certainly not prove the fastest pellets to give the best accuracy! But it does show that the muzzle velocity claims made by Stoeger Airguns for the ATAC are credible and achievable by average production guns, so long as the lightest possible pellets are used to achieve their claimed muzzle velocities.

We’ll continue Gold Service testing with mid-weight X-Field pellets because that more closely represents the weight of pellets chosen by experienced users of these air rifles.


shogun Saturday, 27 September, 2014  

As far as quality, noise control, and power I cant decide between the.22 stoeger atac or the .22 umarex octane. Please help

About This Blog

This blog shares information, ideas and knowledge about air rifles. It compliments the information Stephen publishes on the Archer Airguns website, on YouTube and the Chinese Airgun Forum.

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