I have a Texan SS (.257), a Texan (.357), and a Tex-Rex (.510). I don't seem to have any problems with the .257 when it comes to accuracy, but both the other two, I can't seem to get any consistent grouping even at 50 yards, and I've tried 3 different scopes now. On the .357 which I use the most, I'm shooting NSA 142 grain slugs. The only thing I can figure is that either the slugs aren't terribly accurate, the kick is messing with the shot, or I just plain suck, though as I stated earlier, no issues with .257. I can shoot lids off of drink bottles at 50 yards with no problem, Anyone else have this experience or ideas how to solve? I'm wondering too if adding a Rok-Lok weight stabilizer might help. I do get a little better results if I'm holding the barrel down with as much force as I can comfortably do so and still shoot, but the issue still seems to largely be there. Even though there isn't a lot of kick on the .357 (there's a ton on the Tex-Rex), it's still enough to move the barrel/sights off target.
Airforce Airforce Texan accuracy?
- Thread starter NightKnight
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I keep it on a regulated 3000psi. I haven’t really messed with the spring adjuster but the line is about a millimeter from the barrel
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Try dropping pressure down to say 2200 and work up from there in 50 psi increments. If you have a chronograph you can adjust the power wheel at each step and find the point that the velocity stops increasing with the power wheel increases. It takes time, but worth it when you find the sweet spot.
Also have you slugged the barrel to see what size the grooves are in the rifling. Sometimes just small changes in bullet diameter can make a big difference.
Also have you slugged the barrel to see what size the grooves are in the rifling. Sometimes just small changes in bullet diameter can make a big difference.
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I’ve never slugged a barrel before. I do have a chronograph I just got. May I ask what is wrong with keeping the rifle on a regulated 3000 psi line? Or is the procedure you’re proposing about calibrating the hammer for all pressures?
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The only thing wrong with keeping at 3000 psi is the lack of accuracy.
What you are trying to find is the perfect rifle harmonic node for the bullet you are shooting in your rifle, which will give you the very best accuracy for the rifle.
The process is to set your regulator pressure (say) 2200 PSI. Back off the power wheel towards the muzzle. Shoot with the Chronograph. Record the bullet speed. Adjust the power wheel towards the butt. (say 1/4 turn) Shoot and record the bullet speed. Rinse repeat until the speed stops increasing. At the power wheel position that you do not get a bullet speed increase, is the point you are wasting air and should back off the power wheel 1/4 to 1/2 turn. Note that info with the regulator PSI along with your bullet speed. Also track your targets and accuracy.
Rinse repeat with stepping up regulator pressure and stepping up the power wheel adjustments and accuracy.
This takes time, but it will pay off. It is like developing a hand load for a powder burner with "ladder loads"
If you have a micrometer, measure a bullet diameter. I will then set the bullet on a solid surface and give it a little axial bump with a hammer. It will bulge the bullet diameter just a little. You are looking for just a few thousandths of an inch increase. Once that is done drive the bullet through barrel with a wood dowel rod. Do this with the tank removed !! Once driven all the way through the barrel, measure the diameter of the bullet. This will be the groove diameter of the rifling. You will want your bullets that size. If your bullets are smaller then that, then it can cause accuracy problem.
Then there is always some rifles simply can be more or less accurate with one bullet versus another bullet.
What you are trying to find is the perfect rifle harmonic node for the bullet you are shooting in your rifle, which will give you the very best accuracy for the rifle.
The process is to set your regulator pressure (say) 2200 PSI. Back off the power wheel towards the muzzle. Shoot with the Chronograph. Record the bullet speed. Adjust the power wheel towards the butt. (say 1/4 turn) Shoot and record the bullet speed. Rinse repeat until the speed stops increasing. At the power wheel position that you do not get a bullet speed increase, is the point you are wasting air and should back off the power wheel 1/4 to 1/2 turn. Note that info with the regulator PSI along with your bullet speed. Also track your targets and accuracy.
Rinse repeat with stepping up regulator pressure and stepping up the power wheel adjustments and accuracy.
This takes time, but it will pay off. It is like developing a hand load for a powder burner with "ladder loads"
If you have a micrometer, measure a bullet diameter. I will then set the bullet on a solid surface and give it a little axial bump with a hammer. It will bulge the bullet diameter just a little. You are looking for just a few thousandths of an inch increase. Once that is done drive the bullet through barrel with a wood dowel rod. Do this with the tank removed !! Once driven all the way through the barrel, measure the diameter of the bullet. This will be the groove diameter of the rifling. You will want your bullets that size. If your bullets are smaller then that, then it can cause accuracy problem.
Then there is always some rifles simply can be more or less accurate with one bullet versus another bullet.
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Thnx. I’ll at least take the time with the pressure/power wheel. I’m unable to remove the air tank after using some blu loktite on it 
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I went through the tuning process on my .257 and found 2600-2700 psi and the tuner position that gave me the most fps. What I still don't understand is why shot to shot varies as much as 150 ft/sec on a regulated air line. I'm getting as little as 900 ft/sec and as much as 1070 ft/sec. The airforce techs say this is normal but I don't understand why. I tried to tune my .357 in the same manner but was only getting 600 ft/sec at best with medium grain slugs. Halfway through taking my measurements, the safety locked up, so had to send it in for service.
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I take it you are shooting tethered to a tank with an inline regulator? What regulator are you using? I have seen some regulators slow to come back to set pressure, be inconsistent and even creep has tank pressure decreases.
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You are correct that I’m on tethered line with an in-line regulator. As for brand, I think it is unbranded but is very close in design to the RegMan 2.0. I purchased on eBay but I have not noticed any pressure creep on it. I keep the regular at about 100psi higher than my intended airgun pressure as it seems to require a little more pressure to overcome the line resistance
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Probably not your regulator then. Are you lubing your bullets? Have you cleaned the barrel? Are you shooting only NSA ammo?
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I’m using strictly NSA 42grains. I have not lubed them because they are supposed to come lubed. As for barrel cleaning, only thing I’ve done is fire a number of felt pellets through it (no oil or cleaner). It’s difficult to get anything in there. It’s so tight I can’t feed the slug all the way in with my thumb, but AirForce says this is a good thing
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I would get the gear to clean the barrel as my next move. Seems like you got everything else down.
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