Jump

[Mace Ramsay]

My understanding is that every barrel has its own resonant frequency. We adjust the jump to time the projectile exiting the muzzle as the oscillation is at its minimum. As the barrel is used the throat wears so the seating depth changes. My question is do I keep changing the jump to keep it the same as the throat wears or is it the distance from the ogive to the muzzle that has to remain constant ie leave it alone so the jump increases but muzzle to ogive remains constant?

 

[John VM]

Hi Mace.
Once you find a seating depth that is working for you, I generally leave it till the groups open up and then move it out till it tunes in again. Every barrel, bullet, reamer combo has its preference.
John

 

[Mace Ramsay]

I just fitted a new barrel machined by the gunsmith who made the rifle to the same specs as the previous barrel and I noticed the base to ogive is just over 200 thou different. Grant Lovelock of True Flite in NZ used the same reamer. So I assume that a 284 Win wears that much over 1600 firings

 

[alinwa]

My understanding is that every barrel has its own resonant frequency. We adjust the jump to time the projectile exiting the muzzle as the oscillation is at its minimum. As the barrel is used the throat wears so the seating depth changes. My question is do I keep changing the jump to keep it the same as the throat wears or is it the distance from the ogive to the muzzle that has to remain constant ie leave it alone so the jump increases but muzzle to ogive remains constant?

My understanding is that every barrel has its own resonant frequency. NO, this understanding is flawed

We adjust the jump to time the projectile exiting the muzzle as the oscillation is at its minimum. NO

As the barrel is used the throat wears so the seating depth changes. Somewhat true, some "chase the lands"......some don't

My question is do I keep changing.............. muzzle to ogive remains constant? Noone could possibly measure that, and if they could it has no relevence

I just fitted a new barrel machined by the gunsmith who made the rifle to the same specs as the previous barrel and I noticed the base to ogive is just over 200 thou different. Grant Lovelock of True Flite in NZ used the same reamer. So I assume that a 284 Win wears that much over 1600 firings No, No, No.....while this last assumption is the logical conclusion based on your misunderstanding of the factors involved...... NO!

In the real world of typical gunsmiths two chambers "cut with the same reamer" are very rarely interchangeable. Guns don't "wear" on any dimension a thou per firing. Maybe 1 out of 1000 will allow you to interchange cases back and forth and none of them will tune interchangeably..... And a rifle which had over ten thousand firings ON THE BARREL once won The Super Shoot, one of the world's largest accuracy venues. At eleventy-hundred firings of a thou or more each that poor basterd would have been withdrawn into it's own foreskin so far as to have been impotent

I entered this conversation only because your final (logical?) conclusion could be dangerous. You've been fed some truly heinous information in your learning curve and it's led you to some really odd conclusions.

You seem a logical thinker. The problem with logical thinkers is that they have to get their information either via personal experimentation or from others, and these 'others' are most often a hot mess.

Good luck in your quest for meaningful information but please don't continue down your current thought path. Please broaden your information sources.

Maybe the current kings of this discussion board will stoop to help you but I doubt it ...... several of them will simply tell you "they don't waste pearls on swine" .......... and if I opine further this will turn into an argument as we've some folks here nursing ancient grudges against all forms of logical progression. And I'm firmly ensconced in the "swine" category, happy as a pig in sh!t


That said, there are no other information boards that can help you sort this out. ALL the forums have gone woke.... ALL the forums currently operating are loath to call any one opinion valid over another ...... here you at least do stand a chance of getting your information from actual successful shooters if you can find some in the mood to share.

Reread carefully John VM's reply. That is a good safe methodology he presents.... ie measure and work with what IS with no expectations and assuming NOTHING


sincerely


al

 

[mwezell]

My understanding is that every barrel has its own resonant frequency. NO, this understanding is flawed




al

Sure it does. It's a constant minus the very small change that temp makes on steel. In use, this change is inconsequential to tuning. If temp changes that much, it has a larger affect on powder than the tiny affect on ss, so any change there gets lost in the noise of far more significant change in powder and to a lesser degree, air density. But still greater than the resonant change of frequency of vibration....about 4:1. You're correct, that it plays a tiny part, but it's tiny and other factors are what to monitor. Powder turning from a solid to a gas is a chemical reaction and is far more temp dependent than the change of temp of the bbl.

 

[alinwa]

LOL!!! Mike, I'll give you that.....

Mace, lissen to Mike, he's one a the Good Guys even when he's "disagreeing" with me..... and he shoots smaller holes than me, gener'ly

 

[K Hope]

Sure it does. It's a constant minus the very small change that temp makes on steel. In use, this change is inconsequential to tuning. If temp changes that much, it has a larger affect on powder than the tiny affect on ss, so any change there gets lost in the noise of far more significant change in powder and to a lesser degree, air density. But still greater than the resonant change of frequency of vibration....about 4:1. You're correct, that it plays a tiny part, but it's tiny and other factors are what to monitor. Powder turning from a solid to a gas is a chemical reaction and is far more temp dependent than the change of temp of the bbl.

Temperature: Opinion only.

From Tune: When a shot is fired there is extreme hot, pressurized gasses produced heating both bullet and barrel bore. The bullet and barrel have different coefficient of thermal expansion which over time and round fired, changes the clearances between bullet and bore changing pressure. These pressure changes can slightly change bullet shape and offset bullet CG and or the barrel ID may grow which can affect early bullet inbore tilt and barrel transverse motion. And many other things…..

I think I need a Tuner

 

[CharlieH]

Temperature: Opinion only.

From Tune: When a shot is fired there is extreme hot, pressurized gasses produced heating both bullet and barrel bore. The bullet and barrel have different coefficient of thermal expansion which over time and round fired, changes the clearances between bullet and bore changing pressure. These pressure changes can slightly change bullet shape and offset bullet CG and or the barrel ID may grow which can affect early bullet inbore tilt and barrel transverse motion. And many other things…..

I think I need a Tuner

I'm certainty not an expert and I'll never make the Hall Of Fame but here are some observations.
A stainless barrel 24" long will grow in length .009" with a 70 degree temperature change and yet the tuner makers make their adjustment marks in far smaller increments. If the temperature of the barrel makes no difference, that's puzzling.
People leave their rifles out in the sun while waiting for their relay. A rifle scope is made from aluminum, its thermal expansion is three times the value of steel and it heats way up, then they go under the sheltered firing line and it starts cooling back down. The stock also gets heated.
Then you have the ambient temp that can change 40 to 50 degrees during the match. This affects the scales, powder throwers, ect.

Well I could go on but I'll end with , hell yes temperature makes things change but the beauty is it effects all of us.

You would be far wiser to practice,, practice, practice. A good shooter that can read the wind will beat the finest equipment out there. If you practice you will finally feel things, things you can't describe, but you will know when to pull.

So anyway, I'm offering this for what it's worth for the new shooters.

 

[mwezell]

I'm certainty not an expert and I'll never make the Hall Of Fame but here are some observations.
A stainless barrel 24" long will grow in length .009" with a 70 degree temperature change and yet the tuner makers make their adjustment marks in far smaller increments. If the temperature of the barrel makes no difference, that's puzzling.
People leave their rifles out in the sun while waiting for their relay. A rifle scope is made from aluminum, its thermal expansion is three times the value of steel and it heats way up, then they go under the sheltered firing line and it starts cooling back down. The stock also gets heated.
Then you have the ambient temp that can change 40 to 50 degrees during the match. This affects the scales, powder throwers, ect.

Well I could go on but I'll end with , hell yes temperature makes things change but the beauty is it effects all of us.

You would be far wiser to practice,, practice, practice. A good shooter that can read the wind will beat the finest equipment out there. If you practice you will finally feel things, things you can't describe, but you will know when to pull.

So anyway, I'm offering this for what it's worth for the new shooters.

I agree with all of that but it leaves me with one question....How does having a tuner on the end of the bbl change any of it?

It's a tuning tool. Use it but don't overthink every tiny aspect. Did we ever ask ourselves how much the bbl grew when we adjusted our powder measure to maintain tune? No, we read the groups and made changes or left it alone. Same with tuners. Not to mention it but...70° of change during a match??

 

[CharlieH]

I agree with all of that but it leaves me with one question....How does having a tuner on the end of the bbl change any of it?

It's a tuning tool. Use it but don't overthink every tiny aspect. Did we ever ask ourselves how much the bbl grew when we adjusted our powder measure to maintain tune? No, we read the groups and made changes or left it alone. Same with tuners. Not to mention it but...70° of change during a match??

I agree its better to at least have your rifle tuned at the beginning, whatever method you use.

Yes, 70 degrees seems a bit extreme, but let's see if I can find it. It's 40 degrees in the morning and quickly rises to 80, then the barrel heats up too hot to touch during the warmup and string of fire. That's got to be additional 40 more degrees, probably more. And it's not just the barrel thats heating and cooling, the stock, the scope, the powder measures, everything is changing. Now there are those that are so skilled they have less of a problem with the variations than most of us, but even they have to deal with and minimize the effects of temperature.

I'm not really arguing for or against anything, just rambling like an old man does.