Breech Experiments

[Acer Saccharum]

Rich, since you are a scientist, you might have some good suggestions for setting up parameters that will help reveal the clearest results.

Tom

[Joe S]

I’ve been wondering the same thing as Rich.  Basically, does igniting the powder in a different location affect muzzle velocity?  Does a touch hole at the rear of the charge perform better than the same touch hole located at the front of the charge? 

[LynnC]

I'd love to see the vent location test.

One at the breech face, one at mid charge, and one at the front of the charge.

Same charge, same ball.

In mortar tests conducted in the 1700's by John Meuller, the rear most shot the farthest.  I suspect that getting the most out of your powder charge is to light it from the rear...........................Lynn

[rich pierce]

Rich, since you are a scientist, you might have some good suggestions for setting up parameters that will help reveal the clearest results.

Tom

My skilz are not in physics.  I'm better at making inane suggestions to drive people nuts.  I think the important decisions to be made in the experimental design and execution are:

1) Whether you'll keep distance from ball to muzzle equivalent from setup to setup or overall barrel length (including patent breech) constant.  Just choose. 

2) Whether a longer barrel will give a better opportunity for differences in charge ignition and rate of burn to reveal themselves in a faster ball exit from the barrel.  I realize that if you use one camera, a short barrel may be required to see both flashes.  But since patent breeches were developed for birding guns (I think), a barrel of 28" or longer may be appropriate.

3) How to discern whether a faster exit of the ball is due to faster ignition of the charge, higher velocity, or both.  Can a chronograph be used as well?  

4) Whether variables like charge, granulation, compression of the powder charge and tightness of the ball/patch combination could affect outcomes.  You already have many variables (several breech designs and touch-hole designs) so you'll want to keep as many things fixed as possible.  Since the Nock breech was developed for hunting guns, I suggest a reasonable hunting load that has proven accurate in the barrel of choice.  It may be helpful to seat each ball with the same pressure.

5) If in the end, pan ignition,  touchhole design, or touchhole location (as suggested above) are primary determinants of "speed of ignition" then these variables need to be constant as well.  In guess the Nock breech was usually combined with a touchhole liner, so maybe that is the best way to proceed.

6)  How many reps?  These experiments will take a lot of time.
Larry is very good at figuring out how many replicates are needed to determine whether changing variable causes less deviation or changes the mean in an outcome, or whether no difference is the likely outcome. 

7) Whether the experiements you will conduct could have impact on commerical product sales.  In general, not so many folks are interested in science unless it makes their product look bad or shows a product may not offer an advantage.  If you found out that a drill touchhole was as fast or faster than a popular commercial "fast" touchhole, the experiments may be considered "product testing".  Of course the setup you are using is ideal for testing various touchhole designs as well as breech designs.

[Jerry V Lape]

Richpierce, as I understand the original intention of the test, lock performance including pan shape is being excluded because the timing will start with the flare of gas/flame exiting the touch hole which indicates ignition of the charge in the bore.  Any timing difference arising from lock performance would therefore be kept out of the measurements. 

[Larry Pletcher]

Rich ,
You raise a bundle of issues to deal with.  I tried to address each as best I could.

My skilz are not in physics.  I'm better at making inane suggestions to drive people nuts.  I think the important decisions to be made in the experimental design and execution are:

1) Whether you'll keep distance from ball to muzzle equivalent from setup to setup or overall barrel length (including patent breech) constant.  Just choose.

I suspect this is a relatively simple matter.
 

2) Whether a longer barrel will give a better opportunity for differences in charge ignition and rate of burn to reveal themselves in a faster ball exit from the barrel.  I realize that if you use one camera, a short barrel may be required to see both flashes.  But since patent breeches were developed for birding guns (I think), a barrel of 28" or longer may be appropriate.

Here I suspect we're looking at this from different perspectives.  In the last set of barrel ignition tests, the barrel was 2" long.  No ball was used at all.  The cell at the muzzle simply recorded the "stop time" when gases reached the muzzle.  (The testing was done inside my garage in winter. ) So the gases were not restricted by a ball.  Please take a look are the following 5 minute video that shows the methodology used:http://www.blackpowdermag.com/mb/

If the purpose of the test is to see how rapidly the barrel charge is ignited, probably no change is needed.  If we want to evaluate combustion efficiency, I may be in over my head.

3) How to discern whether a faster exit of the ball is due to faster ignition of the charge, higher velocity, or both.  Can a chronograph be used as well?
 

Here I would not worry about the ball exiting and would only concern myself with ignition time.  If we wish to look at velocities, I'd suggest doing that separately with a chronograph outside my garage. 

4) Whether variables like charge, granulation, compression of the powder charge and tightness of the ball/patch combination could affect outcomes.  You already have many variables (several breech designs and touch-hole designs) so you'll want to keep as many things fixed as possible.  Since the Nock breech was developed for hunting guns, I suggest a reasonable hunting load that has proven accurate in the barrel of choice.  It may be helpful to seat each ball with the same pressure.

I agree that all of these are variables to be controlled.  We would need to measure the charges.  I did this previously using powder from the same can.  Seating pressure and patch/ball tightness were eliminated by not using a ball.

5) If in the end, pan ignition,  touchhole design, or touchhole location (as suggested above) are primary determinants of "speed of ignition" then these variables need to be constant as well.  In guess the Nock breech was usually combined with a touchhole liner, so maybe that is the best way to proceed.

Lock performance will be excluded by igniting the pan with a hot copper wire.  This works well and removes all the variables a lock introduces.  Regarding vent design and location see #7.

6)  How many reps?  These experiments will take a lot of time.
Larry is very good at figuring out how many replicates are needed to determine whether changing variable causes less deviation or changes the mean in an outcome, or whether no difference is the likely outcome. 

Joe Sharber, an ALR member, has assisted me in the past with inperpreting data. He offered to do so here as well. 

7) Whether the experiements you will conduct could have impact on commerical product sales.  In general, not so many folks are interested in science unless it makes their product look bad or shows a product may not offer an advantage.  If you found out that a drill touchhole was as fast or faster than a popular commercial "fast" touchhole, the experiments may be considered "product testing".  Of course the setup you are using is ideal for testing various touchhole designs as well as breech designs.

I already have data that will help us here and help to avoid reinventing the wheel.  In  testing of straight cylinder holes (MB 2000 April),I found that the fastest I could get with a cylinder hole was .0404 seconds (average of 20 trials).  The most recent "Pan/Vent Experiment" was done with a Chambers liner.  That yielded a best of .0360 seconds.  Both used the same barrel stub.  That stub also has a 14/28 hole that could be used for additional liners.  Plus Dan Phariss is sending me a breeched stub for more possibilities.  BTW, the "Pan/Vent Experiment"  mentioned above has been submitted to MB, hoping for a March '09 publishing date.

Rich,  this my muddy the water more than cleaning it up.   The issues about doing this in the garage complicates things if a loaded ball's restriction is necessary for the test.  Photo cells in sun light can be a pain.  I had to block off windows in the garage to get good data.  My opinion  here is that if we are only concerned about ignition speed, a ball isn't necessary.  The gasses exiting the muzzle will work.

I welcome your further comments--
Regards,
Pletch

[Dphariss]

Acer,
Since you mention barrel length, should we measure from vent hole to muzzle or from breech face to muzzle?
 
In my mind I was thinking about doing the flint breech and then cupped (dished) by removing and cupping the same plug. 

Just more things to think about.

Pletch

Hmmm.
Can be looked at 2 ways. 30" barrel is a 30" from tang to muzzle. Does the plain breech gain anything from this arrangement. Longer bore to burn the powder? I dunno if it will or not.
Gee the questions that pop up.
I favor distance from the vent to muzzle for a barrel length. Let the chips fall as they will. I still think the flat breech will finish last.

We may have created a monster.
This is evolving to the point that I wonder if the stuff I hacked out and sent is outdated already. But the barrel stub can be cut and threaded to 3/4 16 and made into a breech of sorts I suppose if needed. Its a cut off from a Badger 45 cartridge barrel so its "the good stuff". I was thinking vent speed when I made it. Then....



Dan

[rich pierce]

I agree it's easy to think up questions and harder to make the calls and do the experiments.  Keep it simple, forget the choronograph experiments or work on them in the future.  Lighting the pan with a copper wire is a good idea.  I brought up the barrel question because I don't know anything about how much time it takes for black powder to ignite and explode.  I suspect based on some videos I have seen that it is readily measurable even with a pistol barrel.  A friend sent me videos of him shooting a pistol and even w/o special equipment I could see the pan light, the flash come from the vent and then the fire leaving the muzzle as separate events.

Experiments like these are invaluable and take the bias and "feeling" out of it. Like a White Lighning touchhole being basically 10-12% faster than a simple drilled hole.  I bet some folks would bet it would be 30% faster.  But improvement is improvement!  If the Nock breech etc gives a 10% improvement, that will be "significant" to many shooters.  Especially target shooters.  If it shot harder with the same charge, that would be exciting for folks who like muzzle velocity.

[Larry Pletcher]

snipped

Experiments like these are invaluable and take the bias and "feeling" out of it. Like a White Lighning touchhole being basically 10-12% faster than a simple drilled hole.  I bet some folks would bet it would be 30% faster.  But improvement is improvement!  If the Nock breech etc gives a 10% improvement, that will be "significant" to many shooters.  Especially target shooters.  If it shot harder with the same charge, that would be exciting for folks who like muzzle velocity.

I think a clay bird shooter could tell the difference in leading a bird with a 10% improvement in ignition speed.

Let's see:
16+% priming against barrel
12% for a White lightning liner
10%?? for a Nock breech
 Pretty soon we'll have the bird hit before the flint stops moving.

Regards,
Pletch