Thank you to our advertisers!







Author Topic: Barrel harmonics and tuning weights  (Read 1506 times))

Offline Aerotulz

  • Shooter
  • *
  • Posts: 30
  • yes
  • Real Name: John Hagan
Barrel harmonics and tuning weights
« on: February 10, 2017, 01:13:18 AM »
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
  • Evergreen, CO

Offline 39M

  • GTA Senior Contributor
  • ******
  • Posts: 2171
Re: Barrel harmonics and tuning weights
« Reply #1 on: February 10, 2017, 01:17:08 AM »
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?
« Last Edit: February 10, 2017, 01:22:01 AM by 39M »
  • Texas
"You'll shoot your eye out kid!"

POWERLINE 35
Blue Streak. 1377. 880
Blackhawk Elite. Daisy 131.
Remington Vantage 1200.
CRUSHER NP.
Torpedo 100x .177

Offline 39M

  • GTA Senior Contributor
  • ******
  • Posts: 2171
Re: Barrel harmonics and tuning weights
« Reply #2 on: February 10, 2017, 01:24:21 AM »
I forgot about the air tube.. :-[

Maybe an additional one or two barrel bands would help?
  • Texas
"You'll shoot your eye out kid!"

POWERLINE 35
Blue Streak. 1377. 880
Blackhawk Elite. Daisy 131.
Remington Vantage 1200.
CRUSHER NP.
Torpedo 100x .177

Offline rsterne

  • Member 2000+fps Club
  • Bob and Lloyd
  • GTA Senior Contributor
  • *****
  • Posts: 25667
  • GTA Forums Person of the Year 2017
  • Real Name: Bob
Re: Barrel harmonics and tuning weights
« Reply #3 on: February 10, 2017, 01:50:50 AM »
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
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline 39M

  • GTA Senior Contributor
  • ******
  • Posts: 2171
Re: Barrel harmonics and tuning weights
« Reply #4 on: February 10, 2017, 01:57:05 AM »
Awe yes. I think Browning used to have an adjustable barrel tuning device. Can't remember what it was called.. ???
  • Texas
"You'll shoot your eye out kid!"

POWERLINE 35
Blue Streak. 1377. 880
Blackhawk Elite. Daisy 131.
Remington Vantage 1200.
CRUSHER NP.
Torpedo 100x .177

Offline Stikman

  • Plinker
  • **
  • Posts: 134
  • yes
    • Air Tanks Plus
  • Real Name: Gene
Re: Barrel harmonics and tuning weights
« Reply #5 on: February 10, 2017, 02:21:12 AM »
B.O.S.S.
  • Sacramento Ca USA
AirTanksPlus.com