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borbal

New BBT "P-Max" internal ballistics program

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Many of you many have used my online external ballistics software at http://www.geoffrey-kolbe.com/external_ballistics.htm

The eventual goal was, '...a collection of ballistics programs will enable the estimation of all the ballistic information needed from "click" to "thump"...' and I have been putting the last brick in place with an internal ballistics simulator.

It is similar to QuickLOAD, which has been around for over 20 years, and the new GRT software which saw the light of day last year, in that it is a numerical simulation using closed bomb data to generate models of powder energy and burning rates. The virtual charge of powder is then 'ignited' and progress of what happens next is determined by the physics. It is purely a numerical simulation and there are no assumptions about peak pressures or muzzle velocities. Unlike these two programs, The BBT "P-Max" simulator can be accessed online using any device with a browser. It does not have to be downloaded onto a device with an operating system for which the program was written.

One thing the P-Max simulator does have in common with QuickLOAD and GRT is that it needs a large library of powder types to be really useful. But that is not easy as powder companies are very reluctant to part with their powder data - particularly US powder companies. The reason is that they do not want to fall foul of the anti-terrorist legislation and so will not release information which might be potentially useful to enemies of the United States. Well, it is early days and so far, I only have the data for the Chemie Swiss "RS" range of powders and a couple of Vihtavouri powders. But it is a start.

Anyhow, you can access the simulator at http://www.bbt.scot/ballistics/pressure.htm

I would be interested to know what you think about it. Is it easy and intuitive to use? Does it give results which are reasonable compared to your experience? One thing you should watch out for is that the case capacities required are the case capacities behind the loaded bullet, NOT the case capacities to the mouth of the case.

Thanks

Geoffrey Kolbe

 

 

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Thank you Geoffery 

 

will take a look and come back 

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I can’t seem to access it using the like although it could be me as I’m in a phone at the moment. 
 

look forward to looking at it in due course though. 

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2 hours ago, borbal said:

Many of you many have used my online external ballistics software at http://www.geoffrey-kolbe.com/external_ballistics.htm

The eventual goal was, '...a collection of ballistics programs will enable the estimation of all the ballistic information needed from "click" to "thump"...' and I have been putting the last brick in place with an internal ballistics simulator.

It is similar to QuickLOAD, which has been around for over 20 years, and the new GRT software which saw the light of day last year, in that it is a numerical simulation using closed bomb data to generate models of powder energy and burning rates. The virtual charge of powder is then 'ignited' and progress of what happens next is determined by the physics. It is purely a numerical simulation and there are no assumptions about peak pressures or muzzle velocities. Unlike these two programs, The BBT "P-Max" simulator can be accessed online using any device with a browser. It does not have to be downloaded onto a device with an operating system for which the program was written.

One thing the P-Max simulator does have in common with QuickLOAD and GRT is that it needs a large library of powder types to be really useful. But that is not easy as powder companies are very reluctant to part with their powder data - particularly US powder companies. The reason is that they do not want to fall foul of the anti-terrorist legislation and so will not release information which might be potentially useful to enemies of the United States. Well, it is early days and so far, I only have the data for the Chemie Swiss "RS" range of powders and a couple of Vihtavouri powders. But it is a start.

Anyhow, you can access the simulator at http://www.bbt.scot/ballistics/pressure.htm

I would be interested to know what you think about it. Is it easy and intuitive to use? Does it give results which are reasonable compared to your experience? One thing you should watch out for is that the case capacities required are the case capacities behind the loaded bullet, NOT the case capacities to the mouth of the case.

Thanks

Geoffrey Kolbe

 

 

Geoffrey, 

I'm not getting '404 not found' with http://www.bbt.scot/ballistics/pressure.htm

Could you check the address?

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Was fine from the link earlier, for some reason its adding a load of random characters into the address when clicked or copy/pastad now, some kind of naming issue.

If you type in the address manually or delete all the crap in the address that appears, it should load ok (or does for me in firefox/opera/chrome).

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Can’t access either 

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I was able to access it, and tried a few examples, but it seems to be way off reference books and QuickLOAD.

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17 minutes ago, Dr. Strangelove said:

This link works for me - http://www.bbt.scot/ballistics/pressure.htm

BlueBoy - which way was the data you got off - too high or too low for velocity and pressure?

My RS60 6.5CM load is (considerably) down on pressure/fps compared to real world actual and QL estimate. But as neither calc accounts for LRP v SRP its probably not the best example; QL doesn't account for SRP brass but the estimated output is inline with my SRP velocity, in spite of SRP usually needing at least an extra grain/grain and a half to achieve LRP fps.

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Thanks GT3_richy

It would be helpful if you could say what your load, case capacity, bullet weight, barrel length was, and what your measured MV was

Thanks

Geoffrey

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1 hour ago, Dr. Strangelove said:

This link works for me - http://www.bbt.scot/ballistics/pressure.htm

BlueBoy - which way was the data you got off - too high or too low for velocity and pressure? 

Data input and result.

image.png.fc75d139db7f1882d695db47e7ab03cc.png

Reload Swiss' data (piezo gauge tested).

image.thumb.png.e6791029585b59d330e1d4bf2ea276f7.png

And the same data put into QuickLOAD.

image.thumb.png.4577b62e048fe42b37a6c4c4a3437f89.png

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Hello BlueBoy69

Well, the data you put into the P-Max simulator was not the same as for QuickLOAD .....

The P-Max simulator required the measured case capacity behind the loaded bullet, in other words the "usable case capacity", which QL says is 42.7 grains of water. So the entered case capacity in P-Max should be 42.7 grains of water, not 48 as you entered.

Try that and see what you get...

Thanks

Geoffrey

 

 

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23 minutes ago, borbal said:

Hello BlueBoy69

Well, the data you put into the P-Max simulator was not the same as for QuickLOAD .....

The P-Max simulator required the measured case capacity behind the loaded bullet, in other words the "usable case capacity", which QL says is 42.7 grains of water. So the entered case capacity in P-Max should be 42.7 grains of water, not 48 as you entered. 

Try that and see what you get...

Thanks

Geoffrey 

 

 

I would suggest you set the input of 'Case Capacity', to 'Useable Case Capacity', as for QuickLOAD the two are completely separate data entries.

Plus measuring the volume occupied by the projectile is not going to be easy. Hence there's a whole area of QuickLOAD that calculates this for you.

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Hello BlueBoy69

Yeah, the problem is that there is not room for the word 'Usable' in front of 'Case capacity'. However, it is explained in the manual (linked to in the explanation text under the data entry form) that by 'case capacity' what is required is the measured capacity behind the loaded bullet. And then there is that little asterisk after " case capacity* ", which if you look to the bottom of the page explains that you need the measured capacity behind the loaded bullet. I guess people will get used to what 'case capacity' means in the P-Max simulator.

I do provide a list of 'usable' case capacities so that people can get a ballpark feel of how the cartridge will perform, also linked to in the explanation text under the data entry form. But you are encouraged to measure the case capacity behind the loaded bullet yourself as that is ultimately the best data of all.

Anyhow, apart from that, did you find the simulator easy to use? Any other comments about using it?

Thanks

Geoffrey

 

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29 minutes ago, brown dog said:

And me now, thanks. How bizarre, what did you change?

I copied it from the thread in handloading! I’m sure someone more intelligent than me could explain why but I’m happy to sit here in my ignorance and be pleased it works!

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42 minutes ago, borbal said:

Hello BlueBoy69

Yeah, the problem is that there is not room for the word 'Usable' in front of 'Case capacity'. However, it is explained in the manual (linked to in the explanation text under the data entry form) that by 'case capacity' what is required is the measured capacity behind the loaded bullet. And then there is that little asterisk after " case capacity* ", which if you look to the bottom of the page explains that you need the measured capacity behind the loaded bullet. I guess people will get used to what 'case capacity' means in the P-Max simulator.

I do provide a list of 'usable' case capacities so that people can get a ballpark feel of how the cartridge will perform, also linked to in the explanation text under the data entry form. But you are encouraged to measure the case capacity behind the loaded bullet yourself as that is ultimately the best data of all.

Anyhow, apart from that, did you find the simulator easy to use? Any other comments about using it? 

Thanks

Geoffrey

 

It seems fine, but the inability for the program in its present state to calculate the space occupied by the rear portion of the projectile means I wouldn't use it personally.

If you can incorporate a few more things so the bullet volume can be calculated by the program, that would improve it somewhat.

To do so I would guess you need to incorporate additional data such as bullet rear profile, overall cartridge length and bullet length. The bullet profile examples would be flat, hollow, boat-tailed (truncated conical) and rebated (a truncated cone smaller than the base diameter), either with various profiles stored (less accurate), or the ability to input additional data from direct projectile measurements (more accurate).

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Thanks BlueBoy69, I appreciate your comments. I will have another think about that word 'usable'.

QL has a library of every bullet ever made and every case ever made and so can calculate the usable case capacity given the COAL. But then, you pay £150 to save you that bother. Harmut Broemel also did all the drawings for all the cartridges and chambers listed by CIP, and so he recycled that work for another market. Good for him. 

The P-Max simulator is free at the point of use but for that, you need to do the easy task of measuring the usable case capacity of your particular cartridge. This is actually superior as it is an actual measurement, not an estimate.

Anyhow, thanks again for looking at the P-Max external ballistics simulator.

Geoffrey Kolbe

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2 hours ago, borbal said:

Thanks BlueBoy69, I appreciate your comments. I will have another think about that word 'usable'.

It is a bit confusing if you've used QuickLOAD before, and to be frank, not a good choice of words. I would have put in useable case if it had said that, it said 'case capacity', which to me means the capacity of the case, not useable capacity after you poke something into it.

2 hours ago, borbal said:

The P-Max simulator is free at the point of use but for that, you need to do the easy task of measuring the usable case capacity of your particular cartridge. This is actually superior as it is an actual measurement, not an estimate.

I concur, far more accurate to measure your own cases, say ten for a good average, or more if you're that way inclined. But to leave the primer in or bung it up with something like wax, or blu-tac, that's the question. In reality, you should really use a primer as there's an additional volume (ullage) there, albeit small, so it should improve volume measuring accuracy.

To be honest, it's not measuring the case volume, that's relatively easy if tedious, it's, as previously mentioned, calculating the volume taken up by the rear of the projectile. Not everyone's a mathematician/engineer/scientist.

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BlueBoy69 said;

"...it's, as previously mentioned, calculating the volume taken up by the rear of the projectile. Not everyone's a mathematician/engineer/scientist."

I think you are thinking about it the wrong way - certainly the wrong way up. I will post a link to a video on the easy way to do it.

 

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3 minutes ago, borbal said:

I think you are thinking about it the wrong way - certainly the wrong way up. I will post a link to a video on the easy way to do it.

Sorry, I've no idea what you're talking about?

Calculating the volume of truncated cones, etc., so you can work out the volume occupied the 'base', not nose of the projectile when inserted into the cartridge case is not everyone's cup of tea.

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As promised, we have made a short YouTube video explaining how to measure usable case capacity.

https://youtu.be/o3eJxKXqmn8

As you will see, it is a very simple process and is really no more difficult that measuring case capacity to the case mouth...

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1 hour ago, borbal said:

As promised, we have made a short YouTube video explaining how to measure usable case capacity.

https://youtu.be/o3eJxKXqmn8

As you will see, it is a very simple process and is really no more difficult that measuring case capacity to the case mouth...

I must admit, I wouldn’t have thought to do it that way! It might be worth mentioning in the video that the bullet needs to be seated to your chosen depth/SAAMI spec in order to measure it. Some people will figure that out, others might not!

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