GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Big Bore AirGun Gate => Topic started by: Aerotulz on February 10, 2017, 01:13:18 AM
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I'm looking for a starting point and how do you decide what to do, how much weight and position on the barrel. Is it all just a swag or is there some known technique to starting out tuning a barrel. I'm shooting a
TJs .308, 14 twist and its 34" long. The barrel mounts to the action with two set screws and a barrel band at the end of the air tube that is 24" from the action, leaving 10" of barrel out past the barrel band. I'm shooting a Nielsen 111 gr. Bullet, sized at .308". I've had varying groups from .850" to 2.5" at 100 yds. Speed has been best at 1028 fps for five shot groups. Also trying 10
wt. silicone lube. Last session was at 950 fps With one or two touching each other and then opening up to 2- 2.5" group. Any experience and help will be much appreciated!
John Hagan
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I think you'd have to put the rifle in a vise to know for sure. Or maybe a lead sled.
Some rifles are just harder to shoot, despite their inherent accuracy.
Another thing, mid mounted barrel banded barrels often produce erratic accuracy(see 1022). But I guess this is where/why the need for a stabilizer?
Maybe you could do away with the band and bed the barrel full length?
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I forgot about the air tube.. :-[
Maybe an additional one or two barrel bands would help?
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There are a couple of ways to go.... You can use a sliding rubber collar (limbsaver) and just try sliding it along the unsupported portion of the barrel.... Cedric (Tofazfou) swears by this method.... Alternately, you could thread the muzzle, and thread on a weight, screwing it back and forth to find a sweet spot.... Fine threads are better, because with that method you often need very small changes in position.... The heavier the weight, the less you need to move it.... If you use 28 TPI threads, each 10 degrees is 0.001".... You need either a lock collar, or a plastic insert in the weight pushing against the barrel threads, to prevent it from self-adjusting.... Some also use a split weight with a clamping bolt.... 1-2 oz. is plenty.... although some rimfire guys use 4-5 oz....
Bob
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Awe yes. I think Browning used to have an adjustable barrel tuning device. Can't remember what it was called.. ???
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B.O.S.S.