The B factor - the bore/overbore factor

[1290]

The consideration of how overbore a chambering is, is a good way, imho, to work out a few worthwhile 'measurements' of a particular chambering. Is it a 'barrel burner' as many refer, is it particularly powerful, is it particularly anemic, is it a good choice for downloading to sub levels (important to some)...will it be economical to load hundreds, perhaps thousands, relative to what you can expect from the performance, etc...

I have worked out a measure of how 'overbore' each chambering is, let it be known as the 'B factor' , the bore factor, by considering a standard chambering, the 223 Rem as it is a global standard, and it is of a mid-field though adequate capacity and power rating (if you like). there are many 22 cal centrefire chamberings of greater and of lesser volume.....and performance e.g. >>22 Hornet>>>223Rem>>220Swift>>

I considered the 308win as the reference (as a standard power level 30 cal), however the 223 Rem would be overbore in comparison, which didnt sound right...so I went 223.

What is this measure you say?

It is simply, a calculation considering the gross case volume, not net volume as the thickness across the case could only be assumed, the external measurements are standardised............ considered RELATIVE to the area where the gasses and bullet leave the case....factored by 100 to give you a percentage relative to the unity (223Rem) simple.... really. Consider the 223 Rem has a B factor of 100 (remember that).

following are the top 10 per chambering type HG handgun, RF rimfire, MA belted magnum, RI Rimmed, RL Rimless, a lot of these are not commonly encountered;

b factor marirl.jpg (101.9 KiB) Viewed 6587 times

b factor hgrf.jpg (70.61 KiB) Viewed 6587 times

Some interesting observations;

The 375H&H and 460Weatherby are 103 and 98 respectively, ie. damn close to the 223 (100).....
The 308Win has a B factor of 96... so a bit less volume relative to the little Rem...
The awesome 310 Cadet has a B of 30...... and its Sambar Legal in VIC!!!
700Nitro scores 100.... its the 223 of 70cals!!
22LR = B of 15
500S&W B=42, 460S&W B=48....
In case you're wondering SE V.H. means Super Express vom Hofe

I'll create a list of the common chamberings and attached a spreadsheet with the full list,
Note as mentioned this considers the gross volume, I considered the case less neck volume but the neck length varies, when there is a neck...some cases have very short or very long necks relative to bore, I will further consider the case less bore diameter volume-volume...... so this is really a talking point exercise if you like....

[1290]

Listing of common rimless rounds, these are the one most recognisable, note this excludes magnum rounds;

b factor rimless common.gif (23.21 KiB) Viewed 6552 times

Yep, the 7mmRUM is up there!!

[anthillinside]

Interesting idea, I think I get it.
It gives you a “potential” for a chambering irrespective of calibre?
For people who like to get into the technical side and do the Ballistic Coefficient calcs you are already at the point of having a full range of specs and data to use.
So if we call BC as the end point of a data set then we could call your B factor the start point, before we have all the powder, calibre, projectile weight etc.?
Am I on the right tram or did I miss the buss?

[on_one_wheel]

Looks interesting but you lost me at " overbore "

[1290]

yes, a potential relative to the bore...Not muzzle energy. Its a measure to compare all chamberings in a standardised method, though it is also useful to compare same or similar calibre chamberings.

As the factor is specific(to a measure) and based on a 223Rem, it compares to the 223 level of potential volume / per bore area.
So a 223Rem has factor of 100. if you double the bore to 44 which squares the bore area therefore a 44cal with the same factor requires 4x the case volume...

Overbore, as in once the ratio is over the ideal (for this purpose the 223Rem ration is the measure, but any could be used) then its overbore...up to the 6.5x68, 460Steyr and 7mmRUM which are the most overbore Rimless cases.... and therefore have the greatest potential in their calibres

If you stick a 22 in the 50Browning, you'll get a B factor of 950......extremely stupendously overbore.....

[Chronos]

Maybe you need to dumb it down a little more for me 1290

I admire your work, you've spent a fair bit of time putting it together.

The b factor is a value but what does it mean in the real world and how might it be applied to measuring efficiency, barrel life etc?

6PPC is extreamly efficient but barrel life is shorter than .223 due to throat erosion.

How might shoulder angle or powder speed and volume influence or even barrel length effect cartridge choice?

It certainly is a can of worms eh?

Chronos

[Rocker]

I have worked out a measure of how 'overbore' each chambering is, let it be known as the 'B factor'

Get onto the people Websters and get that in the dictionary for it to be official

[Lorgar]

Had a bit of free time this weekend did ya?

Interesting though, lets see if the name sticks and you've officially coined a phrase

[1290]

Maybe you need to dumb it down a little more for me 1290

I admire your work, you've spent a fair bit of time putting it together.

The b factor is a value but what does it mean in the real world and how might it be applied to measuring efficiency, barrel life etc?

6PPC is extreamly efficient but barrel life is shorter than .223 due to throat erosion.

How might shoulder angle or powder speed and volume influence or even barrel length effect cartridge choice?

It certainly is a can of worms eh?

Chronos

Chrony, I could get into a heck of a great deal more technical... send you guys nuts, how far down do I need to dumb it??

100 good
120 gooder
150 even gooderer
200 rule goodest but. too gooder

??????/

Hey, I didnt spend that much time... got all the data in front of me...

I'd be surprised if the 6mm was such a barrel burner, unless its being loaded right up there.... as the B factor ( got to use it now) is lower than the 223Rem.... ultimately the gases and solids/unburnt matter, need to exit the case, the ideal from a fluid dynamic POV is the radiused bell mouth - efficient, laminar less turbulent flow (Weatherby used engineering design in his cases) to get the burnt and burning stuff out of the case and as quick as possible with least losses - so an abrupt change will increase the resistance and heat/friction. But to what extent that theory applies to deflagrating propellant..??

This would work against the short column efficient/ consistent burn theory, but who am I to argue with Palmisano... or even Pindel. If I was to design the perfect case? The radiused neck might be in, the shorty case? I never liked them.... and I am a dis-believer in the 'accurate round' theory, there are only accurate rifles

[1290]

Had a bit of free time this weekend did ya?

Interesting though, lets see if the name sticks and you've officially coined a phrase

I've got to do something with the free time... either knitting or thinking up stuff

[Chronos]

Maybe you need to dumb it down a little more for me 1290

I admire your work, you've spent a fair bit of time putting it together.

The b factor is a value but what does it mean in the real world and how might it be applied to measuring efficiency, barrel life etc?

6PPC is extreamly efficient but barrel life is shorter than .223 due to throat erosion.

How might shoulder angle or powder speed and volume influence or even barrel length effect cartridge choice?

It certainly is a can of worms eh?

Chronos

Chrony, I could get into a heck of a great deal more technical... send you guys nuts, how far down do I need to dumb it??

100 good
120 gooder
150 even gooderer
200 rule goodest but.

You're going to have to get real remedial with me now mate, gooderer in what way?

Are you working purely on the assumption that the more powder you can fit behind a bullet with a particular surface area the better?

Chronos

[trekin]

So, what you have done is essentially coined a new name for a formula that wildcatters have been using for years.

[1290]

Chrony, you seem generally switched on enough to work out what it means.....No not necessarily better, it works off a datum, a reference point if you like, being the ratio of volume to bore of the 223, as 'bore'.... its not meant to measure the perfect round or the best but give YOU a standardised measure, what you do with the information is up to you. You can see the PPC is under the 223Rem, so if you like mid-range/mid-potency target rounds it will help You to say, find an equivalent 30cal....

The only assumption is that you can interpret what bore/overbore means relative to a predetermined value/standard...the 223Rem...... if not, sorry, this isnt for you.....

Trekin, it took you 5 days to have a go at at my attempt to add something.... good going...

What/where is this formula that I have plagiarised? I'm well aware that the ratio of volume to bore diameter is a standard consideration, in this form I have never come across, at least not when I sit around the camp fire chewing the tobacci with all those wildcatters that I associate with...

Oh, dont think up another measure of distance, its been done before. What is this metre you speak of? Its not necessary, we have the chain.. Do you know what that is? (off to google )

[trekin]

Chrony, you seem generally switched on enough to work out what it means.....No not necessarily better, it works off a datum, a reference point if you like, being the ratio of volume to bore of the 223, as 'bore'.... its not meant to measure the perfect round or the best but give YOU a standardised measure, what you do with the information is up to you. You can see the PPC is under the 223Rem, so if you like mid-range/mid-potency target rounds it will help You to say, find an equivalent 30cal....

The only assumption is that you can interpret what bore/overbore means relative to a predetermined value/standard...the 223Rem...... if not, sorry, this isnt for you.....

Trekin, it took you 5 days to have a go at at my attempt to add something.... good going...

What/where is this formula that I have plagiarised? I'm well aware that the ratio of volume to bore diameter is a standard consideration, in this form I have never come across, at least not when I sit around the camp fire chewing the tobacci with all those wildcatters that I associate with...

Oh, dont think up another measure of distance, its been done before. What is this metre you speak of? Its not necessary, we have the chain.. Do you know what that is? (off to google )

Mate, consider this as a peer review, that is after all why you posted this on this forum right? As a peer review, you would expect no less than full testing of your theorem, right?
But you are still using the basic volume / bore area formula (x / y = z), are you not? The difference being, the standard consideration defines x as case volume in grains, arrived at by either subtracting the weight of an empty case from the weight of case filled with water, or from case's original factory specs/SAAMI specs. whereas you are defining the volume (I assume in grains) of the case by using the external dimensions, the calculations for which you have not provided. Divided by the area of the cross section of the bore (as in the case of the standard consideration, or the case neck in your calculations). You then factor the product by 100 (x100), why, I don't know, as the only function of this is to move the decimal point two places to the right from what I can see.
From this point I'm going to have to make some assumptions because of the lack of information provided by you as to how you get the figures in your tables, but if it where me, I would make a bar chart scaled in reference to which ever cartridge, in your case the .223 Rem, from which I wish to compare other cartridges to as to whether they may/may not be over/under bore.
Now, is your system, the B Factor, better than the old overbore cartridge formula standard, personally I think not. This chart, shown below, done by a Benchrest Central forum member back in 2010, when rescaled to the .223 Rem and the scale re calibrated by moving the decimal point two places to the right to align with your system, shows an average deviation of only +5 units, for those cartridges tested, when compared to the B Factor system.

And as overbore is a concept and not a law, the minor differences in end results, in my opinion, does not warrant the extra calculations required for your system.

[1290]

By all means, 'peer review' away... but its not an academic paper.. i've done this more so to generate some discussion about the subject, not so much the method to derive it, but thats fine; in the first post I described the following;

It is simply, a calculation considering the gross case volume, not net volume as the thickness across the case could only be assumed, the external measurements are standardised............ considered RELATIVE to the area where the gasses and bullet leave the case....factored by 100 to give you a percentage relative to the unity (223Rem) simple.... really. Consider the 223 Rem has a B factor of 100 (remember that).

- that is 'gross case volume' and why? Gross is the total without deductions, outside measurement because that is the only standardised measurement available.

The description of how its done is enough. Had I included the full calculation I'm sure most readers would develop some instant psychological response..... but please have a go at just the volume part of it, the alpha numerics are the many case dimensions as provided by CIP;

=IF(X324=0;IF(Q324=0;(PI()*(1/3000)*(I324-N324)*(((W324/2)^2)+((AL324/2)^2)+0.25*AL324*W324));(PI()*(1/3000)*(I324-Q324)*(((W324/2)^2)+((AL324/2)^2)+0.25*AL324*W324)));IF(Q324=0;(PI()*(1/3000)*(((G324-N324)*(((W324/2)^2)+((X324/2)^2)+0.25*X324*W324))+((H324-G324)*(((AK324/2)^2)+((X324/2)^2)+0.25*X324*AK324))+((I324-H324)*(((AK324/2)^2)+((AL324/2)^2)+0.25*AL324*AK324))));(PI()*(1/3000)*(((G324-Q324)*(((W324/2)^2)+((X324/2)^2)+0.25*X324*W324))+((H324-G324)*(((AK324/2)^2)+((X324/2)^2)+0.25*X324*AK324))+((I324-H324)*(((AK324/2)^2)+((AL324/2)^2)+0.25*AL324*AK324))))))

How did you go? Do you still want to full calculation?

As far as using grains, that's a mass unit not a volume unit...I've used metric units though it doesn't matter as its a ratio, multiplied by a unitless constant.

I dont know what the 'old overbore cartridge formula standard' is, perhaps imperial units without the ratio part.... I'm not too concerned.

Why 100x? because in my experience, people find a range of numbers easier to absorb/read/consider when there is no decimal point, eg 1.82 versus 182.

The only improvement (future) I'll make to my calculation is as described initially, reduce the volume by a bore-length of bullet from the neck volume, and try to derive a deduction for brass thickness probably from the neck thickness which is a known.

Apart from that, I'm trying really hard to read into your contribution where you're being constructive. Without success. If you don't think there's any value to my work and you prefer someone else's, that is, if you prefer pictures on a graph as opposed to numbers that can be listed and sorted.... great, good luck, I'm happy... that your happy.

Now that we've unequivocally established your opposition or at least lack of interest in this body of work.....no doubt you'll no longer return to this thread, and leave this waste of effort and time to others to contemplate

[trekin]

By all means, 'peer review' away... but its not an academic paper.. i've done this more so to generate some discussion about the subject, not so much the method to derive it, but thats fine; in the first post I described the following;

It is simply, a calculation considering the gross case volume, not net volume as the thickness across the case could only be assumed, the external measurements are standardised............ considered RELATIVE to the area where the gasses and bullet leave the case....factored by 100 to give you a percentage relative to the unity (223Rem) simple.... really. Consider the 223 Rem has a B factor of 100 (remember that).

- that is 'gross case volume' and why? Gross is the total without deductions, outside measurement because that is the only standardised measurement available.

The description of how its done is enough. Had I included the full calculation I'm sure most readers would develop some instant psychological response..... but please have a go at just the volume part of it, the alpha numerics are the many case dimensions as provided by CIP;

=IF(X324=0;IF(Q324=0;(PI()*(1/3000)*(I324-N324)*(((W324/2)^2)+((AL324/2)^2)+0.25*AL324*W324));(PI()*(1/3000)*(I324-Q324)*(((W324/2)^2)+((AL324/2)^2)+0.25*AL324*W324)));IF(Q324=0;(PI()*(1/3000)*(((G324-N324)*(((W324/2)^2)+((X324/2)^2)+0.25*X324*W324))+((H324-G324)*(((AK324/2)^2)+((X324/2)^2)+0.25*X324*AK324))+((I324-H324)*(((AK324/2)^2)+((AL324/2)^2)+0.25*AL324*AK324))));(PI()*(1/3000)*(((G324-Q324)*(((W324/2)^2)+((X324/2)^2)+0.25*X324*W324))+((H324-G324)*(((AK324/2)^2)+((X324/2)^2)+0.25*X324*AK324))+((I324-H324)*(((AK324/2)^2)+((AL324/2)^2)+0.25*AL324*AK324))))))

How did you go? Do you still want to full calculation?

As far as using grains, that's a mass unit not a volume unit...I've used metric units though it doesn't matter as its a ratio, multiplied by a unitless constant.

I dont know what the 'old overbore cartridge formula standard' is, perhaps imperial units without the ratio part.... I'm not too concerned.

Why 100x? because in my experience, people find a range of numbers easier to absorb/read/consider when there is no decimal point, eg 1.82 versus 182.

The only improvement (future) I'll make to my calculation is as described initially, reduce the volume by a bore-length of bullet from the neck volume, and try to derive a deduction for brass thickness probably from the neck thickness which is a known.

Apart from that, I'm trying really hard to read into your contribution where you're being constructive. Without success. If you don't think there's any value to my work and you prefer someone else's, that is, if you prefer pictures on a graph as opposed to numbers that can be listed and sorted.... great, good luck, I'm happy... that your happy.

Now that we've unequivocally established your opposition or at least lack of interest in this body of work.....no doubt you'll no longer return to this thread, and leave this waste of effort and time to others to contemplate

Mate, only too happy to no longer participate in a discussion on ballistics with some one who shows the level of ignorance as shown by yourself, and is too immature to accept criticism from a peer. But before I go, and in a hope that these parting words may educate you somewhat, I leave you with the following lessons:
1 As any shooter who has the most rudimentary grasp of anything to do with reloading knows, the method described in my post of measuring the volume of a case is the standard used across the industry, and is referred to as case volume in grains of water, or liquid volume, or just plain grains.
2 Continuing a discussion with some one who can not read or understand plain English just sh%ts me no end. The Overbore cartridge formula, or ‘Overbore Index’ as a mathematical formula — the case capacity in grains of water divided by the area (in square inches/mm) of the bore cross-section, or as I wrote it, "volume / bore area formula (x / y = z)". In other words the ratio of case volume / bore area. Which, do you not agree is the bases of you B Factor?
3 As for your lack of ability to able to read data from a chart/bar graph, well I can't help you there, but I'm sure that when you get to the right grade at school your teachers will teach you this lesson (was grade 4 or 5 in my day when we were taught this)
And now as I'm finally departing this thread, I'll leave you with this prediction;
when in the future you make the improvements you describe, I predict that the only outcome will be that you figures will now be closer to those in the chart above. But sadly you will be the only one who will not see it, either because of denial, or you inability to decipher data from a chart/bar graph, or perhaps a lot of both.

[1290]

ta taa

[tony m]

I just like the discussion.The endless pursuit of data, you never know what it evolves in too.This is our affordable form of rocket science and if our need to measure stuff ever comes to a halt-so will we.Good going and carry on!