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Let us start fresh on the Barrel Vibration Post
Discussions related to Guns and Firearms

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popgun
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Location: Mitchell, GA, U.S.A. (2007 pop. 191)

PostPosted: Sun May 11, 2008 8:50 pm    Post subject: Let us start fresh on the Barrel Vibration Post Reply with quote

I just deleted 14 pages of hijacking posts and some wet sponge throwing.
Start fresh and keep it on topic.

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gelandangan
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PostPosted: Mon May 12, 2008 12:03 am    Post subject: Re: Let us start fresh on the Barrel Vibration Post Reply with quote

Oh No.. Popgun..
Please dont delete the whole lot..
There are some interesting link and quotes of methods that I havent save yet..
Problem is I cannt remember who said it and what its about, because I am thinking to go through them again later on when not too busy.

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Pumpkinslinger
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PostPosted: Mon May 12, 2008 1:55 am    Post subject: Re: Let us start fresh on the Barrel Vibration Post Reply with quote

LOL! I'm not sure I want to ...

Gelan, I saved those websites on my home computer and will post them here again when I get home.

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Pumpkinslinger
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PostPosted: Mon May 12, 2008 2:04 am    Post subject: Re: Let us start fresh on the Barrel Vibration Post Reply with quote

Hey!! The IT Nazis slipped up tonight!

Optimum Charge Weight >> home.earthlink.net/~da...index.html

Optimum Barrel Time >> www.the-long-family.co..._paper.htm

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Pumpkinslinger
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PostPosted: Mon May 12, 2008 7:31 am    Post subject: Re: Let us start fresh on the Barrel Vibration Post Reply with quote

Since I originated this thread back in March maybe I should try to recap my side of it at least.

My original intent here was to see if there was a way to calculate the best range of seating depth adjustments for a load/gun combination to give the most accuracy you could squeeze out of it and with the least amount of testing. Reading the various books and manuals I have on reloading I saw that there was no hard and fast rule that everyone agreed on. I was wondering if there was an easy way to determine what the best increment for the adjustment is and what the best range of values for testing is. In the original thread there seemed to be a misconception that I thought I could calculate the “perfect load” without testing and this is not true.

NOTE: This seating depth adjustment was intended to be done after you’d found the best powder charge for the load. The Optimum Charge Weight method is the best way to do this that I’ve seen so far. You can find it at home.earthlink.net/~da...velopment/

At first I was looking at the “barrel whip” part of the barrel vibration, hence the thread title. I was thinking of this as a wave length/distance kind of problem. Then some of the good folks here pointed me at the Optimum Barrel Time paper online (http://www.the-long-family.com/OBT_paper.htm) and I realized that it was more of a timing problem. You want the bullet to exit the muzzle at a particular time to avoid the shock wave resulting from the powder charge going off. So I started down that path. Chris Long, the author of the OBT paper, was kind enough to answer my email with some good information. He can explain this far better than I can so I suggest you read his paper. I do know that the QuickLOAD internal ballistics software calculates the changes in pressure/velocity/barrel time when you enter a change in seating depth so I was hoping to find a quick and easy way to approximate it.

Some folks told me that I was ignoring all the other variables and I was, because I was trying to see if I could keep it as simple as possible. I didn't want to have to write a computer program to do it if a calculator would work.

Well, at this point I just can’t see an easy way to do it for two main reasons. As you change the seating depth you change the volume of the combustion chamber. First, if you change the seating depth on a .22 Hornet by 0.001” it results in about a 0.08% change in volume but if you make the same change in a .220 Swift it results in a 0.02% change. So you have to take into account the case volume. Second, as you change the combustion chamber volume you change the pressure and resulting velocity. Seating deeper increases pressure and velocity and seating farther out decreases them. However these changes aren’t linear over a very large change in seating depth.

You know, maybe if I can take the case volume into account and consider the pressure changes linear over a very short range of seating depth adjustments…

Oh well! Wink

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foreign
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PostPosted: Mon May 12, 2008 2:59 pm    Post subject: Re: Let us start fresh on the Barrel Vibration Post Reply with quote

hey pumpkin after reading that paper by chris long i was wondering if you could simply take his calculation for different nodes on different length barrels. that gives you the time that the bullet needs to be exiting the barrel. tha say it takes into account different seating depths. then you simply enter in the powder load that you worked out with OCW fiddle with the seating depth untill the computer says that the change you have made will get the bullet to the end of the barrel at the right time and bingo. im not sure if quickload does give you the timke to the bullet would reach the end of the barrel but if it didnt then that shouldnt be to hard to work out. im sure there must be a lo cure or something that would show the exceleration ect.
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hunterjoe21
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PostPosted: Mon May 12, 2008 3:04 pm    Post subject: Re: Let us start fresh on the Barrel Vibration Post Reply with quote

Pumpkinslinger wrote:
Since I originated this thread back in March maybe I should try to recap my side of it at least.

My original intent here was to see if there was a way to calculate the best range of seating depth adjustments for a load/gun combination to give the most accuracy you could squeeze out of it and with the least amount of testing. Reading the various books and manuals I have on reloading I saw that there was no hard and fast rule that everyone agreed on. I was wondering if there was an easy way to determine what the best increment for the adjustment is and what the best range of values for testing is. In the original thread there seemed to be a misconception that I thought I could calculate the “perfect load” without testing and this is not true.

NOTE: This seating depth adjustment was intended to be done after you’d found the best powder charge for the load. The Optimum Charge Weight method is the best way to do this that I’ve seen so far. You can find it at home.earthlink.net/~da...velopment/

At first I was looking at the “barrel whip” part of the barrel vibration, hence the thread title. I was thinking of this as a wave length/distance kind of problem. Then some of the good folks here pointed me at the Optimum Barrel Time paper online (http://www.the-long-family.com/OBT_paper.htm) and I realized that it was more of a timing problem. You want the bullet to exit the muzzle at a particular time to avoid the shock wave resulting from the powder charge going off. So I started down that path. Chris Long, the author of the OBT paper, was kind enough to answer my email with some good information. He can explain this far better than I can so I suggest you read his paper. I do know that the QuickLOAD internal ballistics software calculates the changes in pressure/velocity/barrel time when you enter a change in seating depth so I was hoping to find a quick and easy way to approximate it.

Some folks told me that I was ignoring all the other variables and I was, because I was trying to see if I could keep it as simple as possible. I didn't want to have to write a computer program to do it if a calculator would work.

Well, at this point I just can’t see an easy way to do it for two main reasons. As you change the seating depth you change the volume of the combustion chamber. First, if you change the seating depth on a .22 Hornet by 0.001” it results in about a 0.08% change in volume but if you make the same change in a .220 Swift it results in a 0.02% change. So you have to take into account the case volume. Second, as you change the combustion chamber volume you change the pressure and resulting velocity. Seating deeper increases pressure and velocity and seating farther out decreases them. However these changes aren’t linear over a very large change in seating depth.

You know, maybe if I can take the case volume into account and consider the pressure changes linear over a very short range of seating depth adjustments…

Oh well! Wink


Why din't ya say that????

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Morax
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Joined: Dec 18, 2006
Posts: 618
Location: Pittsburgh Pa

PostPosted: Mon May 12, 2008 3:30 pm    Post subject: Re: Let us start fresh on the Barrel Vibration Post Reply with quote

ok i glossed over what ya posted PS., and personally you are doing right, fix what you want FIRST then move on from there, you think it is barrel vibration giving you the most trouble then fix that, then go onto the seat depth and then onto primer type, then onto color of shell... yes its all relitive for accuracy, but a properly seated bullet in a vibrating barrel dont mean squat. also if anyone got the new natchez catalogue, on page 78 they have a photo of a limbsaver vibration dampener at work...
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Pumpkinslinger
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Joined: Sep 22, 2007
Posts: 4524
Location: NC foothills

PostPosted: Mon May 12, 2008 5:20 pm    Post subject: Re: Let us start fresh on the Barrel Vibration Post Reply with quote

Foreign, the QuickLOAD software does that. By the way, they also say that its an approximation and had to be tested. I downloaded the demo version and played with it some. Here's an example:

home.comcast.net/~davi..._Devlp.htm

Now I just have to decide whether I want to spend the $150 to play with it more.

Hunterjoe, I was saying that, it just got lost in the noise.

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