Equation for tuning

F

Fred J

Active member
Okay, lets see how you calculate to determine the additional weight needed as a starting point in tuning a new barrel.
Bare barrel shoots 3/4 inch vertical with best ammo.
Barrel = Shilen Octagon, 25 3/4" bore .221"
Diameter at muzzle, .875
Dead spot determined by tapping the barrel and listening for the dead spot = 5.5" from crown.
Tuner = Harrell total weight 8 oz. Threaded for additional weights.
 
Okay, Bob, how did you determine that? Your saying, the Harrel Tuner @ 8 oz is suffient?
 
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Fred: I plagiarized it from another forum. Actually tho I have 2 barrels that come real close to your description, one tunes at 159, the other at 168. No extra weight but adding a Harrels bloop requires only a few clicks if any.....and the bloop weighs 2.0 ounces. bob
 
Years ago, Hoke Kerns wrote an article for PS magazine titled "In 185 I do believe". I collaborated with him in the teting for that article and was given credit for it by him in the text of the article.

Having said that, my 10.5 rifle has a Harrels' tuner on it and it shoots tiny round holes @ 20 and 50. With the Noodle I have on it now, it likes #55 for one lot, # 57 for another and #20 for the third.

My summation is the rifle is probably not in tune; certainly not as BC discribes a Stopped Muzzle. I suspect the real tune is with more weight on the tuner but I am not willing to expend the limited good ammo I have for the rifle to find out.
 
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This appears to be my problem as well. Not tuner setting will repeat. I've also tried Hoke's suggestion, but didn't feel it was getting the most out of this barrel.
 
Shot the worst in a long time. Still waiting on the formula that will get me closer to a starting point.
 
Hopwell method, I suppose you could start out with some lesser quality but nearly the same speed ammo to get close, then the good stuff for a finale. Make sure your bedding is good before starting, otherwise you will be chasing your tail.
 
Tried that and still can't get it close enough to repeat. Beddings good, chamber is very good & bore slugs extremely round with slight taper. Dead spot is 5.5 in from the muzzle. What I am asking, is how do I calculate the amount of weight in ounces, I need to place in front of the muzzle? How is that calculated? I've tried the formulas on the Lilja site but it hasn't provided an accurate answer.
 
Fred J said:
Tried that and still can't get it close enough to repeat. Beddings good, chamber is very good & bore slugs extremely round with slight taper. Dead spot is 5.5 in from the muzzle. What I am asking, is how do I calculate the amount of weight in ounces, I need to place in front of the muzzle? How is that calculated? I've tried the formulas on the Lilja site but it hasn't provided an accurate answer.
Click to expand...

Fred try this...

Barrel dia. of .875 less .221 bore is .654 Dia of solid metal...

use formula Dia squared x 2.67 to arrive at lbs/ft...

.654x.654=.4277x2.67=1.141 lbs/ft...

1.141lbs/ft x 16oz/lb = 18.256 oz/ft / 12"/ft= 1.52 oz/inch...

5.5" from Node center to muzzle end = 5.5" x 1.52 oz/" = 8.36 oz...

Calfee says 1 1/2 times that weight for a total of 8.36 oz x 1.5 = 12.54 oz...

Calfee says place that weight (12.54oz) 1 1/2 times the distance of Node center to muzzle end or 5.5" x 1.5 = 8.25inches from muzzle...

So per Calfee explanation place 12.54 oz at 8.25 " from the end of your barrel muzzle for a "Stopped" barrel...

I think my numbers are correct but please check me out before using...

Hope the info helps

PS...Calfee rings his barrels out of the actions, naked barrel...and is usually between 2" and 3" from Muzzle end to Node center...FWIW
 
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Bolero:
I found a small section of barrel that is similar in diameter ( .8775" by 1.5685" in length. Bore is .2265". Using your formulas, I get a total weight of 2.3656908 ounces. Using a postage scale, it actually weighs 4 ounces. Why the difference of 1.634309 ounces? Could the type of steel be the difference? Not sure what type is.
Fred J
 
Fred, yes the type of steel makes a difference, stainless is heavier than carbon steel...

The info I posted will get you pretty close...

are you trying to use the Calfee method to find the best place to put your tuner...???
 
Not really. Right now, trying to determine how much in length, I can remove from a barrel to make weight. Measure twicw, cut once.
 
Umm, excuse me for asking, I don't want to offend anyone but 3/4 of an in of vertical seems like an awful lot if that's at 50 yards with it's best ammo. I've only re-barreled a couple of dozen rifles but if they didn't shoot under 1/2 groups at 50 yards before putting on a tuner something was wrong somewhere. 3/4 of an inch would never be acceptable in a bare barreled target rifle from any major maker such as Anschutz or Walther. I would think it would be very hard to get a consistent tune with a rifle with that much vertical built in to start with.

Dennis
 
Thanks, Dennis. I rechecked the group, and it's actually .524 center to center. I get better groups on occassion, but nothing for the wallet.
 
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