I have been performing various tests on my .177 caliber Brno TAU-7 air pistol for almost a year now. Tests have included accuracy, velocity and consistency of an unaltered gun.
I do all my accuracy testing with the TAU clamped into a Black and Decker Workmate. This assures that no human sighting error is involved in the test. The gun is carefully loaded and fired while having minimal contact between the gun and my hand. This type of shooting is not as stable as a heavy metal framed machine rest but it is far better than what I can do with a sandbag rest. The velocity of the TAU-7 is variable from 325fps to 600+fps. Throughout my testing I have tried different settings according to the purpose of the test. 

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  For 10 meter shooting I clamp the bulk filled gun in the workmate for the entire session.
Here is a string of 5 shot groups at 10 meters (485fps with 7.3gr JSB Match pellet):

.232", .259", .180", .250", .251", .259", .213", .294", .230", .132"

Average for 10 groups is .230" ctc.
All groups were measured with a vernier caliper and calculated to center-to-center measurement. Groups #2 and #8 had a slight flyer but the 5 shot group was measured and used for the test. All groups are 5 shots.

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For long distance shooting I clamp the TAU in the workmate and hang the 150 gram tank from the grip of the gun using the bulk adapter.
Here are the group measurements shot at 30 and 40 yards (approx 600fps):
(Click here to view picture of the workmate vice holding the Tau-7)
30 YARDS
CR Premier Lt - .95, 1.00, .80, .95, .90 Ave= 0.92"
JSB Exact -      .70, .90, .70, .40, .90 Ave= 0.72"
RWS Super Pt - .75, .80, 1.00, 1.00, 1.10 Ave= 0.93"
(Click here to view picture of the actual 30 Yds.target used )
40 YARDS
CR Premier Lt - .95, 1.20, 1.15 Ave= 1.10"
JSB Exact -    1.05, .75, 1.05 Ave= 0.95"
RWS Super Pt -1.65, 1.75, 1.40 Ave=1.60"
(Click here to view picture of the actual 40 Yds.target used )
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The velocity with the TAU-7 is just as consistent at a high setting as it is with a low setting.
Here are a couple of velocity strings when the TAU is set at high velocity (77 degree temp):

CPL (7.9gr) - 604, 609, 610, 606, 607 Ave= 607fps
JSB Exact (8.44gr) - 599, 600, 603, 599, 599 Ave= 600fps

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Lower velocity settings are more desirable for short distance shooting or indoor 10 meter target shooting. At a lower setting more shots are obtained from a bulk fill or powerlet. Here is a sample of some velocity readings at lower velocity:

7.3 grain JSB pellets:
484, 486, 487, 486, 487, 485, 490, 487, 491, 492, 491, 493, 492, 495, 494, 495, 495, 498, 494, 495.

RWS R-10 pellets: 422, 424, 422, 422, 424, 426, 423, 426, 425, 426.

RWS MeisterK Lights: 434, 423, 430, 430, 430, 428, 432, 428, 431, 433, 433, 429.

The "consistency test" was done with very little time between shots. Maybe 10 seconds between shots. Two different velocity settings were used for this test. The JSB pellet test had a slightly higher setting.

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I always wondered what happens to the velocity of a TAU-7 as the shot count gets higher. Would the velocity be close at shot #5 as it is at shot #50? A true test is the only way to find the answer. Manuals and assumptions are not always correct . 
Here are the velocity readings at the beginning of a bulk fill (7.3gr pellet). Shots #1-5:
487, 485, 487, 490, 493   Here are the readings for shots #31-35: 490, 494, 495, 491, 495

Here are the readings for shots #61-65:
492, 497, 491, 490, 490
  The velocity with the pellet tested was within a 10fps range throughout the test. Velocities fell between 485fps and 495fps.
After 71 shots on this bulk fill the muzzle report was suddenly much lower and velocity dropped off quickly. It was very easy to tell when the liquid CO2 was gone and the gun needed another filling. The lower shot noise coincides exactly with a drop in velocity.

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My final test with the TAU-7 involved shot count for various velocity settings. For 10 meter shooters and silhouette shooters the number of shots per fill can be important. The TAU can be powered with CO2 in three different ways. It is possible to use a 12 gram powerlet, bulk fill the internal reservoir or hang a small tank from the base of the grip. I found the number of shots which I obtained with a good bulk fill was equal to the number of shots obtained with a 12 gram powerlet.
  This should be expected as the internal chamber will easily hold 12 grams of bulk CO2.  When set at 485fps with 7.3 grain JSB pellets I obtained 70-80 shots per bulk fill. I tested one powerlet at this setting and obtained 81 shots before velocity dropped off. During high velocity shooting I did a shot count with the TAU set at 570fps with 7.9 grain CPL pellets at 68 degree temperature. Velocity would have been approximately 600fps with the temperature in the mid to high 70s. The shot count at this setting was about 30 per bulk fill. I obtained as high as 32 good shots. The TAU-7 can also be used with the grey transfer bottle attached throughout the shot. The bottle is attached using the bulk adapter included with the gun. A 3.5 oz paintball tank is the final way the TAU can be used. An adapter can be purchased from Mac-1 to allow this tank to hang from the bottom of the grip just like the longer transfer tank. With hanging tanks the TAU will give hundreds of shots per full tank.

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