TAU-7 Pistol Review

 

By Todd Cooper

 

 

The Czech made TAU-7 CO2 pistol is a moderate priced 10m style match pistol that also functions fine for metallic silhouettes and accurate long distance plinking. The TAU is very versatile and adjustable for velocity, overall weight, balance point, trigger preference, and sight widths.

 

My TAU-7 Standard was purchased in December 2000 and since then has been tested for accuracy, velocity, and consistency. All accuracy testing was done with the pistol clamped into a Black & Decker Workmate to reduce human sighting error. The pellet can be carefully loading and the pistol can be shot with very little contact with my hands. Although the Workmate is not the most stable type of rest, it is better than a sandbag rest and it’s the best arrangement I currently have. A heavily constructed pistol machine rest with proper grip attachments would be the ideal accuracy testing device.

 

 

 

TOPICS OF INTEREST

(Click to follow)

TAU-7 Versions

Accuracy Tests

Velocity Tests

Velocity Consistency

Rapid Shooting Test

Temperature Sensitivity Test

Shot Count Test

Pistol Adjustability

Basic Maintenance

Bulk Filling

Mounting Optics

Shooting Stories

 

 

 

TAU-7 VERSIONS

 

The TAU-7 pistol is available in several different versions. The version that I tested was the plain Standard with an adjustable walnut grip. Other choices include the Silhouette, Sport, Match, and Junior. All TAU pistols come with bulk fill accessories, piercer caps, extra sight inserts, extra seals, screwdrivers, tubular wrench, barrel weights, rear counter weight, and carry case.

 

Standard

no compensator

10” barrel

standard trigger

 

Sport

compensator

10" barrel

improved trigger

 

Match

compensator

10" select grade match barrel

improved trigger

deluxe case

Silhouette

compensator

12" barrel

improved trigger

scope mount

Junior

light-weight compensator

thinner/shorter barrel

 

lighter pistol

 

Tau-7 Standard

 

Tau-7 Sport

 

Tau-7 Match

 

Tau-7 Silhouette

 

Tau-7 Junior

 

Tau-7 Standard Case

 

Tau-7 Match Case

 

Tau-7 Silhouette Case

 

Tau-7 Junior Case

 

 

 

ACCURACY TESTS

 

Many different RWS, H&N, JSB, and Crosman wadcutter type pellets were tested in my TAU-7. The 4.49mm JSB Match light (7.3 grain) consistently produced the smallest groups. Some of the other pellets performed quite well but the preferred pellet was used to chart the accuracy for the pistol.

 

Velocity for the following accuracy test was set at 485 fps with the tested pellet. This velocity was ideal for 10m shooting and usually gave 70-80 shots from a proper bulk fill.

 

5 shot group @10 metres

JSB Match

7.3gr

.23, .26, .18, .25, .25, .26, .21, .30, .23, .13

Ave = .23” ctc

 

Groups #2 and #8 had slight flyers but they were still used for the evaluation.

 

 

For long distance shooting the TAU was clamped into the Workmate and the 150 gram filler hang tank was hung from the grip using the bulk fill adapter. This method allows high volume shooting without the need to remove the pistol for filling.

 

Velocity for the longer distance shooting was set at approximately 600 fps, which was maximum for my pistol. This setting uses much more CO2 for each shot but the hanging tank eliminates the need to continually refill.

 

5 shot groups @30 yards

Pellet

Grain

Center-to-center (inch)

Average

JSB Exact

8.4

.70, .90, .70, .40, .90

0.72"

Cros Premier

7.9

.95, 1.00, .80, .95, .90

0.92"

RWS Super Pt

7.9

.75, .80, 1.00, 1.00, 1.10

0.93"

 

5 shot groups @40 yards

Pellet

Grain

Center-to-center (inch)

Average

JSB Exact

8.4

1.05, .75, 1.05

0.95"

Cros Premier

7.9

.95, 1.20, 1.15

1.10"

RWS Super Pt

7.9

1.65, 1.75, 1.40

1.60"

 

Note: The JSB Exact pellet used in all testing was the 4.50mm version. This was the only version I had at this time.

 

Accuracy was also tested at 10 metres with a high velocity setting of 560 fps with 7.9 grain Crosman Premiers at a temperature of 68F. Only a few groups were shot at this velocity for a quick accuracy check.

 

10 shot groups @10 metres

Pellet

Size (mm)

Grain

Center-to-center (inch)

Cros Premier

n/a

7.9

.31”, .25”, .32”

JSB Match

4.49

7.3

.21”

JSB Match

4.50

7.3

.26”

 

 

 

 

VELOCITY TESTS

 

The TAU-7 velocity is adjustable with the large screw located under the fore stock. This screw adjusts the pre-load on the hammer spring.

 

I have never tried to achieve the lowest possible velocity with my TAU-7 but a friend had his shooting at only 350 fps with match wadcutters. At this velocity the shot count is around 100 or more per powerlet. The velocity likely adjusts lower than 350 fps but not many shooters would desire such a slow shooting pistol.

 

As I mentioned previously, my TAU-7 was usually set at 485 fps with the 7.3 grain JSB Match pellet. For 10m competition I wanted a velocity between 450 and 500 fps that gave around 70-80 shots per bulk fill. This allowed 5-10 sighter shots followed by a 60 shot match on a single bulk fill.

 

Maximum velocity with the TAU was determined by adjusting upwards a little at a time until further adjustments resulted in no further velocity increases. The 10.25” barrel length only allows a certain amount of CO2 expansion until the pellet exits the muzzle.

 

The following numbers were recorded at a temperature of 75-80F degrees.

 

Cros Premier

7.9gr

604, 609, 610, 606, 607

Ave = 607 fps

JSB Exact

8.4gr

599, 600, 603, 599, 599

Ave = 600 fps

 

 

 

VELOCITY CONSISTENCY

 

The design of the valve and gas reservoir will often influence the shot to shot consistency of a CO2 pistol. There are some designs that are heavily affected by fast shooting or drops in temperature. The TAU-7 was tested in both conditions.

 

Velocity Consistency - 30 seconds between shots (68F temp)

Pellet

Grain

Feet per second

JSB Match

7.3

484, 486, 487, 486, 487, 485, 490, 487, 491, 492, 491, 493, 492, 495, 494, 495, 495, 498, 494, 495.

RWS R-10

7.7

422, 424, 422, 422, 424, 426, 423, 426, 425, 426

RWS Meister

7.7

434, 423, 430, 430, 430, 428, 432, 428, 431, 433, 433, 429.

 

Note: The JSB Match was tested with a slightly higher velocity setting.

 

Velocity readings thoughout a 65 shot series

 

Shots #1 - 5

487, 485, 487, 490, 493

Shots #31 - 35

490, 494, 495, 491, 495

Shots #61 - 65

492, 497, 491, 490, 490

 

All velocity readings over the 65 shot series fell between 485 fps and 495 fps with the 7.3 grain JSB Match pellet.

 

After 71 shots on this same bulk fill the muzzle report was suddenly much lower and velocity readings dropped off rapidly. It was very easy to tell when the liquid CO2 was gone and the pistol needed another filling. The lower shot noise coincides exactly with the drop in velocity.

 

 

 

RAPID SHOOTING TEST

 

This was a challenging test because of the time factor involved. The TAU-7 was clamped into my Black and Decker Workmate and the chronograph was placed 20" in front of the pistol. A stopwatch and note pad were placed on the Workmate, beside the pistol. A set of 15 pellets were lined up for fast acquisition. I started the clock and made the shots within specific intervals. There was no reason to focus on the clamped pistol so I loaded, shot, checked velocity, quickly recorded, and repeated…15 times. This simple system should ensure no pistol movement and consistent readings.

 

The 7.3 grain JSB Match pellet and bulk CO2 were used for the complete test. This pellet usually tests at 485-495 fps when shot at a target shooting pace in the same 69F temperature.

 

Velocity readings with 14-22 second intervals

500,492,494,497,501,505,498,499,495,502,502,496,510,501,501

High = 505 fps

Low = 492 fps

Ave = 500 fps

 

5 minute rest break.

 

Velocity readings with 10-15 second intervals

502,500,503,508,504,503,501,502,503,502,502,504,502,501,500

High = 508 fps

Low = 500 fps

Ave = 502 fps

 

5 minute rest break.

 

Velocity readings with 10-15 second intervals

506,505,501,501,504,504,502,499,500,500,503,501,498,501,501

High = 506 fps

Low = 498 fps

Ave = 502 fps

 

The temperature of the TAU CO2 reservoir was getting very cold by the end of this test but velocity didn't seem to be effected. With a balanced valve there is compensation for pressure drops.

 

One fresh bulk fill was used for all the above shooting. There were no “top ups” during the testing.

 

 

 

TEMPERATURE SENSITIVITY TEST

 

The same equipment set-up was used for this test as was used for the Rapid Shooting Test. The pistol was bulk filled at the beginning of the test and left clamped in the Workmate until the testing was over.

 

During the winter months it is very easy to change the temperature in my two floor house. The gas furnace will heat the entire house through a duct system but when only the gas fireplace is used on the main floor the basement is deprived of heat. This was how I dropped the temperature in my shooting area from 70F to 55F without much effort. A thermometer indicated the exact temperature at the time of each test.

 

Two sets of 15 shots each were recorded using 7.3gr JSB Match pellets.

 

Velocity readings at 70F temperature

502, 500, 503, 508, 504, 503, 501, 502, 503, 502, 502, 504, 502, 501, 500

Ave = 502 fps

506, 505, 501, 501, 504, 504, 502, 499, 500, 500, 503, 501, 498, 501, 501

Ave = 502 fps

 

Velocity readings at 55F temperature

498, 502, 505, 505, 498, 503, 504, 508, 501, 498

Ave = 502 fps

 

The 55F temperature was quite cold. I needed a sweatshirt to be somewhat comfortable in the basement but the pistol’s metal was still cold to touch.

 

During the summer months I checked the TAU-7 for temperature sensitivity at the higher end. Velocities seemed to increase by 6-8% when going from 70F to 80F temperatures.

 

 

 

SHOT COUNT TEST

 

The final TAU-7 testing involved shot count for various velocity settings and CO2 storage methods.

 

The TAU pistol can store CO2 in three different ways. It is possible to use a 12 gram powerlet, or bulk fill the internal reservoir, or hang a small tank from the base of the grip. All three methods will work throughout the full velocity adjustment but some methods give many more shots before a refill is needed.

 

For 10 metre target shooting the TAU-7 must be used with powerlets or bulk fill CO2. My main source of CO2 was from a huge 50 pound bulk tank but I checked shot count with one powerlet for data purposes only. The pistol was set at 485 fps with 7.3 grain JSB Match and 81 good shots were obtained from the 12 gram powerlet. This should be enough shots for sighting and a complete 60 shot match.

 

When using bulk fill CO2 I usually get 70-80 shots per fill, depending on the effort put into filling the reservoir. During the consistency test I got 71 shots from a decent bulk fill. The same number of shots is possible with bulk fill or powerlets if the effort is put into getting 12 grams into the reservoir. When shooting the TAU I rarely let the reservoir get to an empty state. It’s an easy task to add CO2 before a shooting session and top it up every 60 shots.

 

During the high velocity shooting I did a shot count with the TAU set at 565 fps with 7.9 grain CPL pellets at 68 degree temperature. The shot count at this setting was about 30 per bulk fill. On a couple of fills I counted 32 good shots.

 

The TAU-7 can also be used with the 150 gram grey transfer bottle hanging  throughout the shot. The bottle is attached with the bulk adapter included with the pistol. A small paintball tank is another way the TAU can be used. An adapter can be purchased to allow this tank to hang from the bottom of the grip just like the longer 150 gram TAU transfer tank. When using a hangy tank the TAU will give hundreds of shots per full tank.

 

With proper adapters it would also be possible to use a remote line from the pistol to a large paintball tank for all day shooting fun. If the plan is stationary target plinking this method might be useful.

 

 

 

PISTOL ADJUSTABILITY

 

The TAU-7 is a very adjustable airpistol and can be set to meet many different needs.

 

The extreme velocity adjustment was already mentioned above. Variable velocity from 325 fps to over 600 fps is possible with the turning of a screw. This makes the TAU suitable for short distance indoor shooting, 10m competitions, silhouettes, plinking, and some small game hunting.

 

The overall weight and balance are adjusted with the 2 extra barrel weights that weigh 2oz each. A removable rear counter weight is another feature which effects balance. This counter weight slides along a metal rod to give the shooter the ability to fine tune the balance of the pistol by locking the weight at a desired location.

 

The front sight comes with 3 different post widths to choose from and the rear sight has numerous notch sizes to try. All the combinations allow the shooter to obtain a desirable sight picture.

 

The trigger on the TAU-7 is 5-way adjustable. Adjustments are possible for: pull weight, 1st stage, 2nd stage, over-travel, and trigger position. The trigger on my pistol was factory set to slightly below 500 grams so I had to increase the tension to make in legal for 10m shooting. The let-off on my particular pistol was very crisp.

 

As is typical with many target pistols, the TAU also has an adjustable shelf on the grip. One screw secures the palm rest against the bottom of the grip.

 

If you are looking for an all-purpose air pistol then maybe the TAU-7 is something for you to consider. The TAU is at home both on the target range and plinking in the backyard.

 

 

 

BASIC MAINTENANCE

 

Before any pellets were fired, my new TAU-7 received a thorough cleaning of all metal parts. The preserving products were removed and a coat of oil was applied for rust protection. Quality lubricants were used on pivot and friction areas.

 

The internal CO2 reservoir was cleaned with paper towels that were twisted in a carrot shape. A light spray of Slick 50 Lube-1 helped loosen the gunk from inside the reservoir. A very thin coating of Pellgunoil was applied to the clean reservoir using cotton patches and a nylon tipped rimfire rifle cleaning rod.

 

The single forearm screw was loosened to allow the forearm to slide forward to access the large velocity adjustment screw and hammer spring. A drop of Pellgunoil was applied to both parts and also to the hammer spring guide rod.

 

The breech latch pivot pins and locking pin should be lubricated to reduce friction and smooth the movements. I use a mixture of Crosman Pellgunoil and Beeman M2M moly paste. About three drops of each are mixed on a plastic surface and applied to the locations. The moly paste seems a little too thick to flow into crevices on it’s own. GunSlick graphite grease and Pellgunoil also mix well together but I prefer the moly paste mixture. Even straight Pellgunoil is better than nothing.

 

All metal surfaces should be wiped down with a very thin coating of a quality oil that will not damage rubber seals. I prefer Slick 50 Lube-1 but other oils may work just as well. If you use Rem Oil make sure it doesn't come in contact with the two breech seals or cap seals, and make sure it doesn't flow into the transfer port at the breech. The Rem Oil can be used on external metal parts if carefully applied.

 

Finally, I apply a drop of Pellgunoil to my finger and give the breech seals a quick wipe to keep them moist. This can be done every few tins of pellets or whenever they look dry.

 

When charging the TAU-7 with CO2 I apply a drop of Pellgunoil to the end of the powerlet that is inserted first. When using bulk CO2 I apply a drop to the valve pin on the pistol’s bulk fill end cap. One drop every second filling (or 2nd powerlet) is enough. If you use regular household oils you will likely get leakage at the pistol's internal valve, and seal damage can occur. I once tried an air tool oil and leakage occurred. Disassembly was required to clean out the oil with cotton swabs before the leakage would stop. That was a lesson well learned.

 

Changing seals on the TAU-7 is a very easy task. The two breech seals on the loading latch are the simplest to remove and they can be popped out with a fingernail or a stiff plastic probe (make something). These seals are simple o-rings and a finger push will insert the new ones.

 

Changing the pistol’s internal seals require removal of the grip. With the end cap removed from the CO2 reservoir, you can use the tubular wrench to unscrew the metal ring that secures the grip. This ring is usually very tight from the factory but leverage can be applied with a screwdriver through the hole in the wrench. Make sure you use the correct end of the wrench to remove the ring. One end has two nibs that fit into notches in the ring.

 

Once the grip is removed, the slotted end plug at the rear of the frame can be removed to access the valve parts. On the end plug there is a rubber o-ring that should be lubricated with Pellgunoil before re-assembly.

 

The valve return spring and valve stem should pull out with a gentle coaxing. Once the stem is removed, you can look into the valve area and see the white valve seal secured into the frame. This seal should not be touched unless it needs replacing. The seal can be removed by carefully threading a couple turns of a long screw into the seal to pull it out. Damage to the seal is inevitable. A ballpoint pen can be used to insert the new white valve seal.

 

The o-ring seal on the powerlet piercer cap is also easy to replace. The C clasp on the end is popped off to access the one seal.

 

The bulk fill end cap has 3 seals. By removing the C clasp the two internal seals can be accessed. The 3rd seal is located in the end and seals around the transfer bottle nib.

 

Valve Stem

 

Valve Seal

 

 

 

BULK FILLING

 

Bulk filling the TAU-7 air pistol is not a difficult task. Only a few basic steps are required to get a good fill of the pistol’s internal reservoir. Once properly filled you should get about the same number of shots from a bulk fill as from a 12 gram powerlet.

 

To get a full fill on the 150 gram grey TAU transfer tank you must put the tank in the freezer for about 15 minutes. Chilling reduces the internal pressure to allow more CO2 to flow into the tank for a better fill. Once the tank is removed from the freezer you should immediately attach it to your large master tank and fill. This approach always seems to work for me.

 

It is best to weigh the 150 gram tank on a small postal scale to be sure you have a complete fill without an overfill. If you happen to over fill, the tank can be drained a bit by removing the fill adapter from the master tank and screwing it onto the small transfer tank for a couple of seconds at a time to drain CO2 until the weight is correct. Keep checking the weight on the scale.

 

The TAU transfer tanks are now 150 grams but older 125 gram tanks are still fairly common. This fill rating is clearly marked on the tanks. The 125 gram weighs 500 grams when empty and 625 grams when full. The 150 gram tank weighs about 620 grams when empty and 770 grams when full. If you find the tanks are not quite full after the first attempt, just use them anyway because it really doesn't matter much. A total weight of 740-780 grams for the 150g tank will be fine.

 

After the small transfer tank is filled it must rest for a bit to allow the CO2 to pressurize the bottle to approx 850 PSI (at room temp.). Filling the transfer bottle after your shooting session might be a good idea.

 

After about 5 good fills from the transfer bottle to the pistol, a bottle “top up” is usually needed from the master tank. Once you get down to about a half charge in the transfer tank the pistol gets more difficult to fill adequately. Sometimes a second dry firing (5-6 shots) is needed to get a good pistol fill when your transfer tank falls below half full. Just fill up again with the master tank and all is well again.

 

To get a good fill in the pistol I do the following:

1 - Cock pistol

2 - Attach transfer tank and invert for 30 seconds

3 - Disconnect tank

4 - Chill pistol's reservoir by dry firing pistol in upright position for 5-6 rapid shots

5 - Invert gun, attach tank, and prop up for 5-10 minutes

6 - Disconnect tank

7 - Rest pistol for 5 minutes to allow CO2 to stabilize

8 - Enjoy shooting

 

At any time during your shooting session the TAU-7 reservoir can be "topped up". The reservoir will already be cool enough (from shooting) to take a good fill so dry firing is not necessary.

 

Contrary to what is recommended, I always store my TAU-7 with a partial bulk fill. After I'm done shooting for the day I leave the pistol pressurized until I shoot again. The left over CO2 is used to dry fire and cool the reservoir before attaching the tank for a good fill. I have had my TAU pressurized for over a year with no leakage problems.

 

Some TAU-7 owners have problems with the seals on the two piercer caps. Using the same cap will usually tear the seal because the absorbed CO2 causes the seal to become brittle. That is why 2 caps come with the pistol. Alternate them.

 

In my opinion bulk fill is the best way to go with the TAU-7. Install the bulk fill cap on the TAU and leave it on. Top it up and shoot away.

 

When shopping for your master tank, try to find one with a siphon tube inside. The siphon tube allows liquid CO2 to come from the bottom of the tank when in an upright position. The CO2 liquid is what you want in the small transfer tank and eventually in the pistol. If your master tank does not have a siphon tube you will need to invert it when you fill the small transfer bottle. Inversion allows the liquid to flow out the master tank when no siphon tube is present. The small transfer tank is always inverted when filling the gun because it does not have a siphon tube inside.

 

Bulk-Fill Adapter

 

150 gram Bulk Tank

 

 

 

MOUNTING OPTICS

 

I know of 3 choices for optic mounts for the TAU-7:

 

1 - Use the factory TAU-7 scope mount. This is a high mount and will work for scope or red dot.

 

 

2 - Drill and tap one of the TAU barrel bands (2oz barrel weight) and fasten a 4" length of scope rail. The scope rail is available in 11mm or weaver size from most gunsmith shops. The rail should also be available from Brownells. This set-up will work for a red dot but is too low for a scope.

 

 

3 - I saw a picture of a TAU-7 with the rear sight top drilled and tapped for a short scope base. The rear sight was adjusted down to the lowest setting and a halo-sight was mounted.

 

 

 

 

SHOOTING STORIES

 

My TAU-7 was originally purchased for online 10 metre postal competitions but long distance outdoor plinking with this pistol is loads of fun. The decent velocity, good accuracy, and sweet trigger all help make hits a common occurrence.

 

Velocity was turned up to 565 fps with 7.9gr Crosman Premier pellets at 68F degrees. At this setting I get around 30 shots per bulk fill.

 

Targets

10oz (284ml) mushroom cans

2.7”D x 3.9”H

22oz (680ml) pasta sauce cans

3.4”D x 5.7"H

28oz (796ml) tomato cans

4.0”D x 4.7"H

 

All shooting was offhand using an isosceles hold and CPL pellets. This type of shooting does not give the best potential accuracy of the pistol but it shows the shootability of the pistol. The TAU-7 is not hold sensitive and was found to be an easy pistol to shoot accurately.

 

Shooting Results

30 yards - 10oz mushroom cans

                 - 7 out of 10 hits

                 - pellet penetrated through one side of the can

                 - can always flipped over with force that gave me satisfaction

 

 

40 yards - 22oz pasta sauce cans

                 - 9 out of 10 hits

                 - again the pellet penetrated one side of the can and it would flip over

 

50 yards - 28oz tomato cans

                 - 7 out of 10 hits

                 - cans would sometimes flip but not usually

                 - pellet would put a heavy dent in the can

                 - about 30-40% of the time a pellet would penetrate one side of the can

 

Regular hold over was not used for this long distance plinking session. To keep the targets above my front sight post I would expose more of the front post above the rear sight notch when shooting the longer distances. For 30 yards I could use level sights and aim dead on for hits. At 40 yards a bit of post was allowed above the top of the rear sight. At 50 yards almost all the post was above the rear notch. This system of sighting allows me to put the can on top of the post for all shooting distances.

 

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