Accuracy Report
For some reason my POI changes in steps as I use up air in the tank. I can understand the pellet dropping but it goes from left to right at the same time. Take a look and try to explain.
Talon SS with 18″ barrel, 100 gr.hammer, stock spring, polished hi-flow valve, JBS 18’s and a 2700 psi fill and a 900 psi end.
The point of aim was the bull but I have it zeroed at 45 yds and I shot at 10 meters indoor using my bipod on a table.
The middle circle is 1″ so it does not look so bad here, but at 50 yds it”s a 4″ spread.
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I have often wondered if it is caused by the changing pressure in the tank.
If perhaps the force of the hammer hitting a valve stem against varying pressure in the tank makes the poi shift for lide to side besides the up and down shift.
Too bad I sold my big regulator I used on my SCBA tanks, when I did tether it it shot much better.
Your right about the heavier hammers, I have always found they and the heavier springs will make it far more difficult to shoot the rifle accurately.
Also I wondier if having a bushing held in by 4 screws rather than 2 would help.
I recently purchased a 18 inch barrel from Tagdagger. I came without bushings, so I ordered a set from Air Force, they were so tight in the frame, I have to put the barrel in a padded vice to put it in or take it out. It also shoots EJ’s better than any barrel I have ever used them in.
Regards,
Roachcreek
Exactly. Sight it in for a 2700psi fill then you have very consistent POI over 28 shots. Not bad for an unregulated gun.
The first 28 shots are in the same area on the target. For me that would mean 28 squirrels. It looks OK to me, but I am old. 🙂 Mine does that too, whien it does I just top off the tank with air.
I’m starting to think that a 100g mass slamming into the breech then valve is causing enough movement to throw off POI as the pellet leaves the barrel ever so slightly, and depending how your gun is held (left hand versus right hand) that might be what is happening.
Say that vibration caused by the hammer hitting has a duration of x milliseconds where your Point of AIM is shifted before it recovers back to your initial Point of Aim. At high velocity, the pellet is travelling down the barrel the within those x milliseconds, so the POI is affected because the gun hasn’t recovered to POA. At lower velocities, there is enough time for the gun to recover from the hammer impact so when the pellet leaves the barrel, the POA has recovered.
Just a theory. Anyone have some super high speed slow motion cameras to test this theory?
Or it could simply be your gun/barrel doesn’t like JSB 18’s. Does it do this consistently with other pellets?
rotating the barrel may change the poi but i can’t see that left-to-right trend with decreasing velocity being affected.
but there are apparent differences of opinion here so, if you do that test, please report your results.
Yes, it has a shroud but it does the same without it, and more amazing, it repeats itself every tank fill. I am thinking about turning the barrel in the bushings about 45 degrees to see what happens.
Maybe you could cut out all thoose sections and make a flip book. You could call it The Walking POI. 😆
Clipping could do that if you have a shroud.
Posters can give you all sorts or reasons about why your rifle is doing this, as to what is wrong with your rifle or what you are doing to cause it.
However it seems to be an ongoing problem with the AF Platform. Many may denie this, but it is a reocurring theme.
And mine have done it also.
Good luck,
Roachcreek
i don’t know anything else that would cause that error and canting to the left would offset (and correct) that left-to-right error.
That would make sense if I was not shooting off of a level table and the the gun has a anti cant on it.
your rifle is canted:
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sight ur gun in for the higher speed ur shooting and stay in that range