Data gathering for barrel design theory

[Webster]

Hello everyone,

I am gathering data to try to explain a certain phenomena. Why do some rifles center of groups trend down or up as velocity increases. The goal of this thread will be to develop a calculator that reliably calculates barrel length and profile required to produce a flat or general downward trend in group position as velocity increases.

In this thread I would like you to post your load development targets if you meet a few criteria listed below.

PLEASE READ THEM ALL BEFORE POSTING DATA

1. You know the dimensions of the barrel. Use format below in inches. (please include the chambering as well ex. 308 win, 6br, ect..)

View attachment 1296066
Sporter and
View attachment 1296067

2. The muzzle is unthreaded and no weights were attached to the barrel (THIS INCLUDES MAGNETOSPEEDS) This makes calculations much easier.

3. The scope is untouched while shooting groups. No adjustments to elevation or windage made between groups.

4. The barrel is completely free floating to the action/ recoil lug.

5. More than one shot per charge level.

6. Make sure you know what range the target was shot at.

7. Need to have bullet and powder used and powder charges listed.

8. Each group needs to be identifiable to correlate to a charge level.

9. Average velocity for each group or velocity for each individual shot in the group.

10. Barrel steel type. Stainless or chromoly

BONUS POINTS not needed but helpful.

1. If you have group center position relative to POA from on target or similar software.

2. Photo of the rifle in the configuration the load dev was run in.

example:
View attachment 1296084
View attachment 1296086

Thanks guys.

Guys that compete in serious BR matches don't have low or high shots in a group. I wonder why? Don't understand what you would calculate with your data. Barrel vibration patterns can be very complicated. Not willing to look t up but it might be covered in Tony Boyers book.

 

[darkangel_r2]

I know you will need exit timing, but you are not asking for enough information, without reverse engineering the load, to achieve a stated velocity/time relationship. That's what drew the original question, and your response below. Your statement, not mine.

If you're planning on just guessing things like, seated depth, case capacity jump and jam, it seems like creating a lot of extra work that introduces extra variables, that ultimately will cast shadows on results.

Generally in test like this, complete load data is considered essential. Trying to understand why you don't feel you need it.

A significant increase in jump or even jamming when matched to velocity (jam at 2700fps vs jump at 2700 fps) your difference is on the order of 2% variation in barrel time. The order in which we are working on this is not a large source of error. Target window 15-20 times larger than that error. If people want to include distance to lands that's nice but it doesn't need to be required. I will add it as a bonus points number though. Doesn't hurt that's for sure.

 

[darkangel_r2]

Guys that compete in serious BR matches don't have low or high shots in a group. I wonder why? Don't understand what you would calculate with your data.

A barrel length and profile for any caliber and bullet I want that makes it so the vertical dispersion plateaus at close range trend flat or down as velocity increases.

Barrel vibration patterns can be very complicated. Not willing to look t up but it might be covered in Tony Boyers book.

That's one I haven't read. Got a link or is that one still in print?

 

[RegionRat]

That's one I haven't read. Got a link or is that one still in print?

https://www.rifleaccuracybook.com/

(He needs prayers and good vibes from all of us right now. He was in a bad accident and was hurt bad. There is a thread on the general page that gives updates.)

https://forum.accurateshooter.com/threads/prayers-for-tony-boyer.4051250/

 

[darkangel_r2]

https://www.rifleaccuracybook.com/

(He needs prayers and good vibes from all of us right now. He was in a bad accident and was hurt bad. There is a thread on the general page that gives updates.)

https://forum.accurateshooter.com/threads/prayers-for-tony-boyer.4051250/

Saw that thread earlier. Bad deal, praying he gets better.

 

[darkangel_r2]

https://www.rifleaccuracybook.com/

(He needs prayers and good vibes from all of us right now. He was in a bad accident and was hurt bad. There is a thread on the general page that gives updates.)

https://forum.accurateshooter.com/threads/prayers-for-tony-boyer.4051250/

Books on its way. There goes the weekend.

 

[tomswede]

Before gathering all that data a way to get started would be to model one or two of your own barrels and then ping test them to evaluate what accuracy your frequency and mode shape calculations.
If there are problems at this point you have a chance to evaluate the feasibility of this project or try to refine to BC’s to get better correlation to the test data.

 

[Webster]

Because the trend I am hunting for is so general (is it going up, down, or staying flat as velocity increases) enough worked examples and a FEA of the lowest order vibration mode adjusted to fit raw data should suffice. That is why the goal for this calculator is extremely limited. Lowest order only no threads, tuners or breaks, and free floated.

The best thing to get accuracy is a top quality barrel and high quality bullets. Anything else is a long journey to the finish line. 95% of the competitors at the Super Shoot are only using two brands of barrels. Look at the equipment list of the competitors.

 

[Northridge]

I've thought about that as well. Varmint AI talks about stock stiffness in his Estens rifle page. What he is saying it does is it delays the barrels response to recoiling into the stock.

Vaughn said something similar though he put a literal shock absorber in between his stock and recoil lug.

I'm assuming a similar effect could be achieved with a stiff stock and a very soft recoil pad. Though that may depend on the weight of the stock. Light and stiff might work but heavy and stiff probably would not.

soft stocks are very tunable just different, stiff stocks are tunable also they just handle differently, as to the recoil pad in light recoiling platforms the pad or lack of pad really has zero affect on overall ladder response. adding or removing items from stock naturally can play a roll but overall characteristics of stock will not change, stiff is stiff soft is soft Lol. it is a fun pursuit the game of tuning and shooting..

Shawn Williams

 

[Webster]

Most mechanical properties are similar between the to eachother in each class. Common stainless steels used in rifle barrels have very similar properties. Same thing with chromoly.

I think the variance of mechanical properties between the two is more of a difference than the variance in properties for the types commonly used in each category.

Sounds like OCD to me. Time better spent somewhere else.

 

[Dusty Stevens]

Sounds like OCD to me. Time better spent somewhere else.

In the 70’s these guys had CB radios in their house

 

[joshb]

In the 70’s these guys had CB radios in their house

With “extra power” ? What did they call those things? Skippers? Jumpers? They could talk to guys 100 miles away, woohoo!

 

[Dusty Stevens]

With “extra power” ? What did they call those things? Skippers? Jumpers? They could talk to guys 100 miles away, woohoo!

Linear amp

 

[Stan Taylor]

Linear amp

Breaker Breaker ya got a copy.Lol

 

[joshb]

Breaker Breaker ya got a copy.Lol

Hey! Where are ya, good buddy?
I’m on the Pa. Turnpike.
What ya haulin?
Manure.
Great! Well....uh....have a good trip!

 

[darkangel_r2]

With “extra power” ? What did they call those things? Skippers? Jumpers? They could talk to guys 100 miles away, woohoo!

I've got a few ham radios. Its repeater stations. You can program the repeaters frequency into your transmitter then repeater towers bounce it around. There are chains of these across the country. I can sometimes hit people on the coasts from Minnesota.

 

[Bc'z]

In the 70’s these guys had CB radios in their house

Good to have you back.

 

[Fuj]

Anybody tested a fat carbon wrapped barrel ?? I had a
notion of having Bartlein doing a Mack truck axle for me.
It would seem the dissimilar materials would have clashing
harmonics and changing up the game. And saying a much
stiffer barrel with less weight. And it is strange that since
the carbon wrapped barrels have been out awhile, you don't
see any hard core test related data posted on these forums.

Always wanted to do a barrel shaped like a Bethlehem Steel
I-Beam.

 

[RegionRat]

And it is strange that since
the carbon wrapped barrels have been out awhile, you don't
see any hard core test related data posted on these forums.

Likely you won't see that data till long after any profitable patents have expired...

Always wanted to do a barrel shaped like a Bethlehem Steel
I-Beam.

Funny you should say that... it turns out the electromagnetic rail gun folks think so to....

 

[Webster]

Hey! Where are ya, good buddy?
I’m on the Pa. Turnpike.
What ya haulin?
Manure.
Great! Well....uh....have a good trip!

Don't follow close decal on the back.