Data gathering for barrel design theory

[Northridge]

Well, I suppose I can add to the confusion or the question at hand. it is my finding that the barrel may play a small role or even a larger roll in what I call static pre-_load to the stock or platform while laying in battery in a natural state, how much pre-load naturally depends on weight of barrel and length I suppose. but more direct to your question what builds ladders that trend down before trending up while increasing charge is a direct link to how soft or flexible a stock is. softer stocks will resist vertical climb for a given charge window vs there stiffer counter parts I find they simply ladder differently. it is my opinion from what i see in a soft stock that it will hold a natural center or point of aim before bouncing up the page now if two soft in the horizontal plain you will see more horizontal dispersion but with the correct combination of both will make a excellent platform. as i increase charge the stock will see more force under recoil compressing stock down hence the point of impact trending down first before springing up the page.

Shawn Williams

 

[darkangel_r2]

Well, I suppose I can add to the confusion or the question at hand. it is my finding that the barrel may play a small role or even a larger roll in what I call static pre-_load to the stock or platform while laying in battery in a natural state, how much pre-load naturally depends on weight of barrel and length I suppose. but more direct to your question what builds ladders that trend down before trending up while increasing charge is a direct link to how soft or flexible a stock is. softer stocks will resist vertical climb for a given charge window vs there stiffer counter parts I find they simply ladder differently. it is my opinion from what i see in a soft stock that it will hold a natural center or point of aim before bouncing up the page now if two soft in the horizontal plain you will see more horizontal dispersion but with the correct combination of both will make a excellent platform. as i increase charge the stock will see more force under recoil compressing stock down hence the point of impact trending down first before springing up the page.

Shawn Williams

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.

 

[243Mendoza]

I disagree. Finite element analysis can work fairly well for most barrel contours. I simply need real world data to tune the models.

FE is steady-state analysis, you need a unsteady analysis code with forced input (bullet and gas travelling down the barrel).

 

[Homerange]

Stock variability will only add further uncertainties to what your trying to achieve which can only skew results.
Either mount it rigid or do free recoil.

Decades ago one of the first barrel makers in NZ had his actions mounted on a 4x4 timber block some 2' long that just sat on the ground/mound/bench and sear release was accomplished with a camera cable shutter release.
At that time his 10 shot .308 groups held NZ records so he must've had some idea what he was doing.

 

[darkangel_r2]

Stock variability will only add further uncertainties to what your trying to achieve which can only skew results.
Either mount it rigid or do free recoil.

Decades ago one of the first barrel makers in NZ had his actions mounted on a 4x4 timber block some 2' long that just sat on the ground/mound/bench and sear release was accomplished with a camera cable shutter release.
At that time his 10 shot .308 groups held NZ records so he must've had some idea what he was doing.

Free recoil is the model. I was talking about in practice once the rifle is built i can speed up or delay the vibrations with adjustments to the stock.

I remember seeing a picture of a barreled action stuck in a raw plank of wood thinking what the hell are they doing. I guess they knew.

 

[Homerange]

Free recoil is the model. I was talking about in practice once the rifle is built i can speed up or delay the vibrations with adjustments to the stock.

I remember seeing a picture of a barreled action stuck in a raw plank of wood thinking what the hell are they doing. I guess they knew.

Good.
I'm talking 40+....actually nearer 50 years back when I was just a tot when this chap used to come here from the city to check his barrels. A fine engineer he was too and had made his own barrel boring and rifling equipment. We became friends after pop had brought me one of his hand built .38 muzzle loader Hawken rifles for my 21st which at that time (1980) also held NZ records for 10 shot groups.
I well remember the day he went home in disgust when a particular 308 bull barrel/load wouldn't do better than 1 MOA when IIRC his record was .358" !
The poor chap karked it from a heart attack @48 and all the gear was sold off and eventually became property of TrueFlite.

True-Flite

www.truefliteriflebarrels.co.nz

 

[tomswede]

By “heat”, I’m referring to the melt lot of material. There is also the “heat treat” of the material, but that may not be a Factor.

There is also the issue that barrels vibrate in three (or more) axes. All of them affect the bullet. The math and the software isn’t there yet.

Agree, I would argue that the current FEM codes can do it ( given enough computing power) but the major issue is as you say the properties input and the BC’s.

 

[dellet]

How/will you be able to sort out loads that are shot out of the same rifle, same bullet, that have the exact same velocity, but different pressure curves, exit times, and recoil impulses?

 

[KMart]

I'm not talking about an individual vertical POI node. I want higher velocity vertical nodes to be the same or lower impacting than slower vertical nodes. I want this to happen with an unmodified barrel.

Define unmodified. ALL barrels are modified along the process of manufacturing, threading, chambering, cutting to length, crowning, etc, etc.
If it is not modified now, it soon will be. You haven't even thrown in the differences in actions, stocks, cartridges and bedding.
This process you are going through, will be like wiping your azz on a wagon wheel. There will be no end to it.

 

[darkangel_r2]

How/will you be able to sort out loads that are shot out of the same rifle, same bullet, that have the exact same velocity, but different pressure curves, exit times, and recoil impulses?

Same bullet, same velocity in same rifle will be treated as having same exit time and recoil.

 

[darkangel_r2]

Define unmodified. ALL barrels are modified along the process of manufacturing, threading, chambering, cutting to length, crowning, etc, etc.
If it is not modified now, it soon will be. You haven't even thrown in the differences in actions, stocks, cartridges and bedding.
This process you are going through, will be like wiping your azz on a wagon wheel. There will be no end to it.

Literally just not threaded at muzzle with nothing hanging off the free floating barrel.

Actually its fairly simple i have a pre-made code and I'm just going to adjust the parameters until all the rifles that go up are on the correct side and the ones going down are on the correct side. Simply need more data than I have.

 

[KMart]

Literally just not threaded at muzzle with nothing hanging off the free floating barrel.

Actually its fairly simple i have a pre-made code and I'm just going to adjust the parameters until all the rifles that go up are on the correct side and the ones going down are on the correct side. Simply need more data than I have.

So, none of these things will have an effect on how the barrel works/shoots?

Define unmodified. ALL barrels are modified along the process of manufacturing, threading, chambering, cutting to length, crowning, etc, etc.
If it is not modified now, it soon will be. You haven't even thrown in the differences in actions, stocks, cartridges and bedding.

Well then, you are just looking for someone that will talk to you.

 

[darkangel_r2]

So, none of these things will have an effect on how the barrel works/shoots?

Define unmodified. ALL barrels are modified along the process of manufacturing, threading, chambering, cutting to length, crowning, etc, etc.
If it is not modified now, it soon will be. You haven't even thrown in the differences in actions, stocks, cartridges and bedding.

Well then, you are just looking for someone that will talk to you.

Tell me the goal of this thread. I posted it. What am I looking to do?

 

[JFrank]

From the last thread you we’re trying to pick a barrel for a hunting rifle. Did you get that ordered up yet?
What distances to you shoot now ? I’d like to hear of your accomplishments and see some of your long range targets.

 

[darkangel_r2]

From the last thread you we’re trying to pick a barrel for a hunting rifle. Did you get that ordered up yet?

Not yet, thats going to be the test barrel for this calculator. I've got a custom profile that's looking very promising. I just want to fine tune it a little with more real world data than what my own rifles supply me with. And if it works I'll post the calculator. If it doesn't work i'll try to add more controls from precise measurements of my own rifles and see if it fits better with the next one made.

What distances to you shoot now ? I’d like to hear of your accomplishments and see some of your long range targets.

I will PM you as I'd rather not post things irrelevant to this threads topic in here.

 

[SweaterDood]

Same bullet, same velocity in same rifle will be treated as having same exit time and recoil.

I understand this reasoning from the perspective of building a model, but this will be neither accurate nor precise. The pressure curves of different burn rates can yield the same velocities from a given bullet/barrel combination without having the same exit timing. Even with the two different loads tuned to shoot the same velocity and in a tight group, there is likely a different exit timing.

 

[darkangel_r2]

I understand this reasoning from the perspective of building a model, but this will be neither accurate nor precise. The pressure curves of different burn rates can yield the same velocities from a given bullet/barrel combination without having the same exit timing. Even with the two different loads tuned to shoot the same velocity and in a tight group, there is likely a different exit timing.

I do list powder used as a requirement. I must have I misunderstood your question. All loads will be run through gordons/QL to extract timing. If anyone ever posts one.

 

[dellet]

I do list powder used as a requirement. I must have I misunderstood your question. All loads will be run through gordons/QL to extract timing. If anyone ever posts one.

The original question was quite simple, but I will try and re-phrase it.

You will only have three constants
Same rifle
Same bullet
Same muzzle velocity.

You will have these variables and more
Different pressure curve
Different exit time
Different muzzle pressure
Different recoil pulse.

Will you be able to, if so how, isolate point of impact change due to barrel profile instead of any of the other variables?

You're going to need a lot more load data than you have asked for, based on your answer changing from using the same exit time, to calculating the exit time.

 

[darkangel_r2]

The original question was quite simple, but I will try and re-phrase it.

You will only have three constants
Same rifle
Same bullet
Same muzzle velocity.


You will have these variables and more
Different pressure curve
Different exit time
Different muzzle pressure
Different recoil pulse.

If I have bullet, powder, powder charge, barrel length, and muzzle velocity I can generate an accurate barrel time from gordons/QL. All the above were in the requirements.

Will you be able to, if so how, isolate point of impact change due to barrel profile instead of any of the other variables?

The only external for at least close range tests (range shot at is a requirement) that would make a large impact is aero jump. I'm assuming its constant over the course of shooting a load dev target. Not a great assumption but few people have wind direction and speed at each shot so we work with what we have.

The rest is internal. Harmonics and velocity. If we know velocity I can solve for harmonics. Then its just adjusting parameters to have best fit to data.

You're going to need a lot more load data than you have asked for, based on your answer changing from using the same exit time, to calculating the exit time.

I thought you meant small variations in the same load if I based my timing on an average velocity and not every sample in that group (example 308 win 175 smk 43.5 gn varget average 2700 fps 24" barrel) I wouldn't care that I didn't get es/sd numbers along with that info.

With the requirements as posted in the OP I can extract barrel time for any round which Is what I always intended to do. That's the only way I can overlay exit times on a muzzle orientation graph.

You thought I meant every shot with the same velocity and barrel length would get the same timing? I wouldn't need requirement 7 then. Its there for that reason.

 

[dellet]

View attachment 1296266
If I have bullet, powder, powder charge, barrel length, and muzzle velocity I can generate an accurate barrel time from gordons/QL. All the above were in the requirements.

The only external for at least close range tests (range shot at is a requirement) that would make a large impact is aero jump. I'm assuming its constant over the course of shooting a load dev target. Not a great assumption but few people have wind direction and speed at each shot so we work with what we have.

The rest is internal. Harmonics and velocity. If we know velocity I can solve for harmonics. Then its just adjusting parameters to have best fit to data.

I thought you meant small variations in the same load if I based my timing on an average velocity and not every sample in that group (example 308 win 175 smk 43.5 gn varget average 2700 fps 24" barrel) I wouldn't care that I didn't get es/sd numbers along with that info.

With the requirements as posted in the OP I can extract barrel time for any round which Is what I always intended to do. That's the only way I can overlay exit times on a muzzle orientation graph.

You thought I meant every shot with the same velocity and barrel length would get the same timing? I wouldn't need requirement 7 then. Its there for that reason.

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.

Same bullet, same velocity in same rifle will be treated as having same exit time and recoil.

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.