We do button rifling been doing it that way for 73 years why change now.
Which barrel profile would act stiffer?
- Thread starter darkangel_r2
- Start date
So I ran the analysis, the dimensions of the chamber complicates the calculation but since the first 1.75" of the barrels is the same and both are mated to and supported by the receiver in that length I think can safely remove it from the comparison analysis.
After that only the neck area of the brass is strange but it is close enough to bore dimension and is present on both so again for comparison purposes think it can be eliminated and we can have a strait bore dimension for the comparison calculation. Only the exterior dimension needs to vary for our comparison to yield an accurate result.
If you want to do these comparisons yourself you can boil it down to a cross section view and use center of mass of right trapezoids and area of right trapezoids to do calculations for any barrel profile.
riflebarrels.com
math.stackexchange.com
Assuming assumptions and my calculations are correct the other items in cantilever beam rigidity are the same for both so we don't actually care what those number are if we only want to know which is stiffer. The light Palma barrel has a 1.3% higher total moment of inertia.
EDIT: INCORRECT ROUNDING ERRORS BUILT UP AND CHANGED VALUES SLIGHTLY. The LV is .15-.5% stiffer than the LP but its 6-7% heavier.
Since they are the same length and material all the other factors drop out and LP should actually act very slightly stiffer despite being almost 7% lighter. This is only a model of course but with everyone who has had both saying they are similar its nice to see that the model also puts them so close together.
A good rule of thumb for barrel profiles with these models is if you are waffling between two profiles of similar weight, the one that's thicker at the muzzle should be stiffer in the model.
Unless someone else wants to check my work I will be going with light Palma or standard Palma depending on how much weight I want on the gun.
Thanks guys.
After that only the neck area of the brass is strange but it is close enough to bore dimension and is present on both so again for comparison purposes think it can be eliminated and we can have a strait bore dimension for the comparison calculation. Only the exterior dimension needs to vary for our comparison to yield an accurate result.
If you want to do these comparisons yourself you can boil it down to a cross section view and use center of mass of right trapezoids and area of right trapezoids to do calculations for any barrel profile.
A Look at the Rigidity of Benchrest Barrels - Lilja
While there are a number of factors that determine the accuracy of a rifle barrel, one of the more critical elements is its stiffness or rigidity. Obviously the larger in diameter a barrel is, the stiffer it will be. Almost as obviously, as the length of a barrel increases it becomes more...
Right Trapezoid - Geometry Calculator
Calculations of geometric shapes and solids: Right Trapezoid.
rechneronline.de
Center of mass of Right angle Trapezoid
Given bases $a$, $b$, and the height $h$. Get the $M(x,y)$ coordinates formula from point $O(0,0)$, where $M$ is center of mass. Wiki has a formula for $M(y) = \frac{h}{3}\frac{2a+b}{a+b}$. And I'm
Assuming assumptions and my calculations are correct the other items in cantilever beam rigidity are the same for both so we don't actually care what those number are if we only want to know which is stiffer. The light Palma barrel has a 1.3% higher total moment of inertia.
EDIT: INCORRECT ROUNDING ERRORS BUILT UP AND CHANGED VALUES SLIGHTLY. The LV is .15-.5% stiffer than the LP but its 6-7% heavier.
Since they are the same length and material all the other factors drop out and LP should actually act very slightly stiffer despite being almost 7% lighter. This is only a model of course but with everyone who has had both saying they are similar its nice to see that the model also puts them so close together.
A good rule of thumb for barrel profiles with these models is if you are waffling between two profiles of similar weight, the one that's thicker at the muzzle should be stiffer in the model.
Unless someone else wants to check my work I will be going with light Palma or standard Palma depending on how much weight I want on the gun.
Thanks guys.
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Well its not a cracked flex plate. Well at least not alone, retaining bolts are tight. Small metal bits floating in oil pan. Rod knock or piston slap is likely. Assuming rod knock as the sound was louder on the underside of the motor right near the torque converter. Going to get a junk yard motor and rebuild it over the winter. I'll replace the rod bearings in the mean time to see if that quiets her down in the interim.
And BTW after building the methodology for the first barrel the process of calculating a "relative" moment of inertia for any barrel is really fast. Like 2-3 minutes fast.
You alluded to Lilja a few posts back. Here's his barrel weight and stiffness calculator. It's pretty simple and spits out a relative number regarding stiffness. I guess he could call it "barrel stiffness for dummies", like me.
I've also made a fixture that I screw the barrel into and put the fixture in a vise. I then hang a weight at the muzzle end and measure deflection with a dial indicator. Ultimately, it gives usable data, as do your calculations and Lilja's software.
Juist download the program and plug in the barrel dimensions.
Computer Software - Lilja
We have five files available as a free download as indicated below. These are zipped files. Bullet Design Calculation Program – Available in two formats: Free Download as an Excel file or Free Download as an .exe file- more information on this software.Benchrest Barrel Weight Calculation Program...
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Nice, that makes quantitative comparisons between different lengths very easy. Mine was a short cut method that only works to compare barrels of the same length.You alluded to Lilja a few posts back. Here's his barrel weight and stiffness calculator. It's pretty simple and spits out a relative number regarding stiffness. I guess he could call it "barrel stiffness for dummies", like me.
Juist download the program and plug in the barrel dimensions.
Computer Software - Lilja
We have five files available as a free download as indicated below. These are zipped files. Bullet Design Calculation Program – Available in two formats: Free Download as an Excel file or Free Download as an .exe file- more information on this software.Benchrest Barrel Weight Calculation Program...
A fine addition to my collection.
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I didn't see your reply before I added to my post about measuring muzzle deflection with a dial indicator. Just another way to the same end.
looks like the contoured barrel file doesn't do a stiffness calculation. I might try to write that calculation into it.
...maybe.
For standard length action (non-magnum) a medium heavy barrel is more than enough. For the ones you mentioned that would be a standard Palma.
You do realize that no matter what calculations you make, or what barrel is stiffer or not, that you are still going to have to tune your load to the harmonics of that particular barrel I assume.
I have seen wide nodes on everything from a pencil barrel to a straight barrel.
I think you are continuing to over think this
I have seen wide nodes on everything from a pencil barrel to a straight barrel.
I think you are continuing to over think this
Amen
Yes individual barrels vary. That statement while true doesn't give anyone any information that can help them make a decision.
I think you're overthinking about the amount of thinking I do.
I'll post an excel file here later with the comparison tool I made.
The first one was on paper. Now I'm just posting a tool to help my fellow shooters.
There are plenty of OCDs in this sport so I am sure some will use it. Lol
With all due courtesy, your analysis and spreadsheet isn't going to give anyone any information worth looking at either. You have received a lot of good advice and suggestions from the forum. The fact that you are not willing to consider that expert advice does not make your calculations any more relevant by putting them in excel.
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