barrel pressure

[bjmac]

Does anyone know of a tabulation (spreadsheet or hardcopy) of the actual breech pressure and corresponding 'backward force' (kick) for long guns? Or a formula for calculating same?

[Dave Faletti]

Look in some of the modern reloading books.  I think Sierra had a good write up on it but I don't have my copy anymore.  The  recoil is dependant on the momentum of the projectile, powder and mass of the gun.  A few other factors will influence the apparent recoil but you can get a decent number to compare with a gun you have shot.

[bjmac]

Thanks , Dave that is the kind of info I'm looking for. Any other suggestions?

[elk killer]

if i remember right,, i think Sam Fadala wrote up some such stuff,,
in the Complete Black Power Handbook back in the early 80s

[flintriflesmith]

This free on-line recoil calculator is very useful. There is no direct relationship between breech presure and recoil.


Think "equal and opposite reaction" instead.


http://www.beartoothbullets.com/rescources/calculators/php/recoil.htm

Gary

[smylee grouch]

If I remember corectly there was a recoil calculation chart or formula in one of the major reloading manuals some years ago but it might have been derived using IMR powders and not Black powder. Some one else on this forum might know of it and respond here.   Smylee

[Chris Treichel]

Here is an interesting article which also gives how to calculate muzzle energy, velocity, recoil, pressure etc

http://www.quarry.nildram.co.uk/ballistics.htm

[Dphariss]

Does anyone know of a tabulation (spreadsheet or hardcopy) of the actual breech pressure and corresponding 'backward force' (kick) for long guns? Or a formula for calculating same?

Recoil is related to muzzle energy.
But note that BP produces significantly more recoil for a given ME than smokeless. As a result my 16 bore rifle makes more recoil than a smokeless powder breechloader shooting the same bullet weight at the same velocity.
A look at the old Winchester velocity tables from the era when cartridges were loaded with both will show a 45-70-405 Smokeless load making 12.27 ft lbs. The same cartridge with the same velocity loaded with BP makes 15.21. This will vary somewhat with cartridge and bullet weight but BP always makes more recoil for a given energy in the same cartridge.
See "Cartridges of The World" 5th ed. pg 136. This was reproduced from "the Ideal Hand Book No. 17 printed circa 1906"
So any formula used to calculate recoil is going to be wrong for BP loads unless allowanced are made.

Dan

[Jerry V Lape]

The only difference between blackpowder recoil and smokeless powder recoil is that the total mass of the ejecta has to be accounted.  Smokeless powder propellant weight is significantly less than blackpowder weight to achieve the same velocities.  To calculate the recoil accurately you would need the weight of powder and projectile (including lube weight and any wadding or patches) as they are all part of the ejecta.   Pressure is not incluced in the calculation directly.  The result of pressure is accounted for in the velocity it produces with the ejecta. 

[Chris Treichel]

Thank you, that is very interesting.

[eddillon]

Here are couple of screen shots of a software program called QuickLOAD.  Note that 19.6 grains of IMR Trailboss results in the same velocity as 66.4 grains of GOEX FFg.  The recoil calculation is based on the Trailboos load.  The recoil fron thhe FFg load would be slightly greater for two reasons:
1.   A greater mass of propellant and propellant gasses move along with the bullet in the FFg load.
2.   Because the burn rate of the FFg is greater than the burn rate of the Trailboss, the rise to peak pressure and   the subsequent acceleration of the bullet is faster, more recoil is apparent.
PRESSURE/VELOCITY

RECOIL

[Daryl]

Does anyone know of a tabulation (spreadsheet or hardcopy) of the actual breech pressure and corresponding 'backward force' (kick) for long guns? Or a formula for calculating same?

There is no single formual for calculating pressure or recoil of black powder firearms that I am aware of. There are programs that can help, maybe, such as quick load, but have shown to produce errors, sometimes quite dramatically - in modern ctgs. when dealing with pressures. How they work with BP, I have no experience or idea.

The recoil formulas given in most loading manuals which utilize bullet weight, weight of rifle and the weight of propelling charge,  give dramatic errors when used with black powder rifles, and even more so with black powder muzzleloaders. This is  mostly due to the difference in energy per grain produced between BP charges compared to smokeless powder charges, along with the differences between individual rifles which can have a dramatic effect on the outcome.

For example, the loss of pressure at the breech is a consideration not taken into account. It is different, literally for every gun - different pressue seating the ball itself, on the powder charge will change the ballistics.  Different patch thickness also makes a difference. Use of a wad makes a difference. A different nipple hole and shape, different vent diameter & shape will make a difference in ballistics, internal and external. What difference is made just by the different shape of the inner chamber in a vent, vs. just a drilled hole of the same shape - length of end-hole will have a difference. There are too many variables in our rifles, so I sincerely doubt a 'pat' formula would work well. Changing any of these can be shown on a simple chronograph to make a difference, thus the pressure and recoil will also be different.

On top of all of this, there are the different makes of black powder and granulations which will also all give different results to each other.  Unlike modern ctg. guns, there are too many variations to be workable - maybe.

[Dave Faletti]

Recoil is considered to be the kinetic energy of the rifle.  You need to find the momemtum of the bullet and for the powder.  The momentum of the rifle will equal the momentum of the bullet and powder.  The kinetic energy will not be equal. Knowing the mass of the rifle its KE can be calculated.  The biggest catch is knowing the momentum of the powder.  When it exits the bore it will be going faster than the projectile which amounts to a higher effective momentum.  That will be the biggest error in a calculation.  Recoil calculations are best kept to comparing somewhat similar weapons of different bore sizes and similarly proportioned powder.  Comparing a 50 cal to a 69 is useful if you are considering a new rifle to build.  The errors will track each other in about the same proportions.  Rifle design can create a huge variance in how the recoil feels with rifles with identical recoil energies.   I found another source at home.  Lymans Reloading Handbook has a section on pg 449 of the 46th edition.   If you are comparing two muzzleloaders with decent barrel lengths you can assume the powder is going the same speed as the projectile.  That will simplify things and the errors will track well enough for a comparison.

[eddillon]

For Daryl,
With smokeless powder, reasonable knowledge of how QuickLOAD works and reasonable inputs into the program by the user you can expect accuracy within +/-  5%.  The black powder estimator in QuickLOAD  takes into account the granulation and brand of the powder or black powder substitute.  Different brands with the same granulation have different results.  There certainly are other  factors that are introduced into mix that are beyond the ability of any prediction software.  The black powder estimator is based on the work of a PhD at Lawrence Livermore Labs that was published in Precision Shooting in 1997-1998.0  The black powder estimator usually is within 150 ft/sec of actual velocity (I say "actual" but then, how accurate is the chronograph?)  Your points about the variables of our rifles and their ignition are well taken.
Ed  

[Daryl]

Ed - I was going on what the fellows I chum with on another site noted, wildcatters, like me, with more money and more toys - who use the program with our various wildcats & small bore ctgs. They acknowledge error up to 30% on pressure in 'some' of the rounds we play with, to the point they had the ctgs. checked by a company with proper pezio equipment.  They prefer to trust the pezio rather than formulation.  The biggest errors were high, which would make the readings non-threatening.  Had  they been short, nasty things could have happened.

It is good to hear of the variations taken into acount by the program, when dealing with black powder. I wasn't aware of that.

[bjmac]

Holy cow! I was just thinking that I could build a .45 cal rifle for my DIL ( she is 90 lbs soakin wet and all of 5' tall) that would have a small recoil for deer hunting. My initial thought was a wider butt plate and a more stout butt overall, with a barrel length of somewhere around 34". Perhaps that is haw I should have phrased the question.
By the way, the programs offered are very informative. Thanks alot.

[Daryl]

By all means make a rifle for her in .45, with the nice wide butt and a fairly straight but proper drop at the comb.  The easiest to shoot, nicest shooting, lowest felt recoil, are the English and German designs. So a Marshal-type rifle in an American design, or English sporting rifle would give the best of the best shooting results.

Felt recoil is very much different that what the numbers portrait, and depends much on the stock's design, especially when making light weight rifles.

[bjmac]

Thanks for that info, Daryl. I do think that I will look into the Marshal and the English and German designs.