Which barrel profile would act stiffer?

[darkangel_r2]

Silly question

Why?

 

[KMart]

I can bust out my mechanics book and do a moment of inertia calculation and throw it into a cantilever beam equation to get a mathematically accurate answer but I was kinda hoping there were some lads on here that have owned both that could just tell me how they act to save myself a few hrs of work.

But it would be really cool to see it done for real. In fact it would be really cool to do it from all the way from strait to sporter to see how much each walks around with the same load dev loads at each profile. Same chamber and length the whole time.

Would be really cool to see what that impacts.

Well, it has now been about 3.5 hours since this thread has started. If you had started your book work then, you would have the answer you wanted from a trusted source by now.

 

[joshb]

INTJ answered your question. You’re just coming off as argumentative.
I have Medium Palma barrels, Light Varmint barrels and Remington Varmint profiles. They all act pretty much the same. POI changes slightly as charge weight increases. I own one straight bull. It moves around the least.
You said Walt was wrong. He’s right. Your target shows it.
Why do you have the “length pegged at 24”? Why not 20” Why not 20 1/4”
Do your calculations. I hope you get a satisfying answer.

 

[darkangel_r2]

INTJ answered your question. You’re just coming off as argumentative.

He did give me an answer. They are likely so close that there will be no noticeable difference. That doesn't change the fact that there is a right answer. I am not and I will die on that hill.

I have Medium Palma barrels, Light Varmint barrels and Remington Varmint profiles. They all act pretty much the same. POI changes slightly as charge weight increases. I own one straight bull. It moves around the least.

Pretty much as i figured.. Have you noticed tighter groups from barrels with more metal around the crown?

You said Walt was wrong. He’s right. Your target shows it.

My barrel threw 5 charge levels into one hole and 5 into another hole. He said different loads have different poi regardless of barrel profile. I had 2 poi for 10 different loads. Unless you consider charges that group together to be one load. Then yes I would have 2 loads and 2 poi.

Why do you have the “length pegged at 24”? Why not 20” Why not 20 1/4”

I'm concerned about how complete a burn I can get with 4350 class powders out of a barrel less than 24". If you read the op im planning a 6.5 creed or 7mm08. So thats the powder class I will likely be using. I have a good amount of h4350, re16, and staball 6.5.

Lilja did the same analysis I will do.

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...

riflebarrels.com

 

[darkangel_r2]

Well, it has now been about 3.5 hours since this thread has started. If you had started your book work then, you would have the answer you wanted from a trusted source by now.

I'm not at home until the weekend. Also I have a 2001 Cherokee with a cracked flex plate that needs replacing. Thats probably going to need to happen first.

 

[tsyarnall]

.................... it would be really cool to see it done for real. In fact it would be really cool to do it from all the way from strait to sporter to see how much each walks around with the same load dev loads at each profile. Same chamber and length the whole time.

Would be really cool to see what that impacts.

Knock yourself out.

 

[Lone Hunter]

Not trying to be a smart azz but everything I have read is “you already have the answers and everyone else is wrong.” I don’t understand why you ask this except just to be argumentative. You have some very experienced people, even a barrel maker, telling you the way to go yet you continue to argue with them. Okay, I will solve this problem for me.
Ignore List here you come.

 

[darkangel_r2]

Knock yourself out.

Don't have a laithe but I'd throw some cash at someone willing.

 

[JFrank]

What effects poi shifts the most on our hunting rifles is a combination of powder or bullets that they just dont like. Contour only makes a difference when they heat up, a well tuned rifle at our ranch doesn't shift much.

 

[darkangel_r2]

What effects poi shifts the most on our hunting rifles is a combination of powder or bullets that they just dont like. Contour only makes a difference when they heat up, a well tuned rifle at our ranch doesn't shift much.

Good info. Notice any change in the width of an accuracy node with change in barrel profile?

 

[JFrank]

No Sir

 

[Bc'z]

Have you noticed tighter groups from barrels with more metal around the crown?

I've shot my smallest 3 shot group with a factory sporter out of a $400 rifle.
I've yet to get 1 of my custom barrels to match it.
Part of the problem could be I'm saving my optimum powders for a rainy day.

 

[INTJ]

I can bust out my mechanics book and do a moment of inertia calculation and throw it into a cantilever beam equation to get a mathematically accurate answer but I was kinda hoping there were some lads on here that have owned both that could just tell me how they act to save myself a few hrs of work.

But it would be really cool to see it done for real. In fact it would be really cool to do it from all the way from strait to sporter to see how much each walks around with the same load dev loads at each profile. Same chamber and length the whole time.

Would be really cool to see what that impacts.

There is a reason benchrest, the discipline that requires the most accuracy, use straight taper barrels. With that in mind, I would pick their Varmint contour over the ones you listed.

 

[darkangel_r2]

There is a reason benchrest, the discipline that requires the most accuracy, use straight taper barrels. With that in mind, I would pick their Varmint contour over the ones you listed.

Thats probably a little heavy for what I'm thinking. Was hoping to be in at about 4lbs for the barrel. LP, LV, SP are right around there thats why I picked those specifically.

 

[Stan Taylor]

Here ya go if you want to stay in the weight range of 4 lbs.
Numbers 3 thru silhouette by the length that suit’s you your good to go.

 

[darkangel_r2]

View attachment 1286110Here ya go if you want to stay in the weight range of 4 lbs.
Numbers 3 thru silhouette by the length that suit’s you your good to go.

Thanks for the info.

 

[joshb]

“That doesn't change the fact that there is a right answer.”
This is where you are lost. You have gotten replies from shooters with extensive experience telling you you’re down to a coin toss.
You can buy the best barrel, have it chambered by the best gun Smith in the land and there is still the possibility that it won’t shoot.
By the way, since you seem intent on splitting hairs, this is NOT “the same point of impact”:
This is close but not perfect for a 5 shot group.

 

[darkangel_r2]

“That doesn't change the fact that there is a right answer.”
This is where you are lost. You have gotten replies from shooters with extensive experience telling you you’re down to a coin toss.

That's why I'm going to do beam member analysis using lija's format to see if there is any difference between the LV and LP.

You can buy the best barrel, have it chambered by the best gun Smith in the land and there is still the possibility that it won’t shoot.

I know.

By the way, since you seem intent on splitting hairs, this is NOT “the same point of impact”:
This is close but not perfect for a 5 shot group.

If I remember right 6 charge levels (18 shots) went into the right hole. .3 grains apart. 1.8 grain difference between top and bottom. Group size varied from .7 to .2 but center of each 3 shot group moved very little.

4 charges (12 shots) went into left hole 1.2 grain spread. Again group size varied but the center of each 3 shot group moved very little. left and right split right at 2790 fps. This was a factory 6.5 creedmoor sav 12 lrp. It cost $800. It holds well below 1/2 moa vertical at 1k consistently for 5 shots.

So I had 2 points of impact. The right one had 6 charge levels falling into it with minimal center of group movement. The left had 4 charge levels with very low center of group movement.

Its got a low node at 2760 and a high node at 2810. I was using the high node but I think its taxing my brass too much as some of my primer pockets feel a little loose after 4 firings. I'm going to back it down to the low node to preserve brass.

Is your med palma the same as standard palma? Do you put recessed crowns or target crowns on your hunting rigs?

 

[ebb]

The one that will shoot the best is the one with the least stress in the blank and the best internal dimensions period. A heavier conture may be better as the barrel heats up, but I doubt it will matter much. The bullet doesn't touch the out side it is influenced by only the inside.

 

[BoydAllen]

Seems to me that all you would need to do is note the shift(s) and adjust your scope as needed every time you change loads.