Two UNPROVEN thories about flint ignition

[Larry Pletcher]

These two ideas have been floating around in my mind for some time and i wonder what your opinions are.  These are related to the "Reliability vs Accuracy", but I didn't want to hijack the topic.

First relates to vent size and accuracy.  I talked with Joel Gard (Bevel Bros.) about his opinion about accuracy going south as the vent eroded.  We know that velocity lowers as the vent enlarges - nothing new there.  If the shooters accuracy load  happened to be at 1500 fps, and his larger vent lowers velocity to 1350, perhaps it's a simple matter to increase the load and get back to 1500 fps.  This is probably an over-simplification, but has anyone tried to get back to the accuracy load by increasing velocity rather than swaping out the vent?


The other thought is how we think of the pan charge and the barrel charge.  Normally we think in terms of one charge igniting the other.   This seems normal especially in barrels with a cylinder shaped vent.   But how close do the two charges have to be before we think of them as a single charge?  For instance we install a vent that has a web .025" thick.  If the pan priming is only .025 away from the barrel charge, maybe it's not two charges at all - just one charge.  In my mind if we prime the pan close up against the barrel we really have only one charge that simply extends into the barrel.

Just unproven ideas,
Pletch

[Tom Currie]

How much, if at all, does the force of the gas venting from the vent hole affect accuracy horizontally ? If it does, I could see that getting worse as the vent hole increases.

[Jerry V Lape]

Tom, are you saying we need equal and opposite vent holes on our rifles? 

Larry, the powder in your pan (the outside charge) is not contained in a pressure vessel and therefore can't  increase the pressures created by the main charge.  If you are suggesting the outside charge is anything other than a match to ignite  the main charge you will have to deal with the lack of containment of that charge.  If you want to test this  fire enough loads with a flintlock in the normal fashion to measure velocities (and thereby indirectly pressures).  Then remove the pan and ignite the main charge with a kitchen match held close to the vent but not plugging it.  Might have to turn the barrel on it's side to let the flame reach the main charge, but I doubt that will be necessary. There won't be a difference in the velocities. 

[hammer]

Larry, a very good question.  I love this stuff.

In Volume III (Ammunition and Performance) of Small Arms of the East India Company  1600-1856 by D.F.Harding the author writes extensively of their testing of their range of flintlock firearms in the 1840's.   Particularly because of the high incidence of  failure to ignite the main charge.  Many factors were discovered including that new arms had a slightly smaller than optimum touch hole (about 1/14th inch in military arms) to allow for erosion over prolonged use (muskets were only replaced every 15 years).  As the touch hole enlarged so ignition noticably improved till it became too large for the safety of adjoining soldiers.  They were surprised in their testing to find that as the diameter increased there was no effect on accuracy (this would have been by their standards, of course).  

My theory on this is that velocity can be affected by the efficiency with which the main charge burns.  (A bit like the difference you get between using a $#@* powder and say Swiss powder.  Swiss will catch better and burn quicker and produce higher pressures).   A larger touch hole can mean a more effective initial ignition of the main charge , resulting in a more efficient burn of the main charge.   A better burn gives a more speedy and even build up of pressure, etc, even with a possible slightly greater loss through an enlarged touch hole.  
 
Or/and a speedier initial ignition and faster burn means less flinching and so gives appearance of no degradation of accuracy?  Either way ..........

Peter.

[JTR]

I can see where an increasing size vent hole could lead to a slower velocity, and consequently your gun no longer shoots to the same aim point. And with less power I would guess.

I guess it was an old time problem as well, because I've seen a few rifles with small bushings in the vent holes. And no, not from a flint reconversion, but a tiny bushing to reduce the size of the vent.
I have no clue how many shots it would take to burn out a vent, so will leave that to you guys that shoot them.
John

[northmn]

One thing about flintlock ignition is that it is probably not consistant like the flame from a cap.  Does the same amount of flame set off the main charge every time?  Does it matter? Personally I doubt that the flame hits the powder equally, but there might be that amount that sets it off and the rest is blown back. Its kind of like the sparks off the frizzen.  You only need enough, I am sure that more do not make much difference.  That is why I think the bigger locks may be more reliable.  Also would a 5/64 vent in a 32 make more of a difference in velocity than a 5/64 in a 54 or larger?  The 3/32 vent in a .75 Bess is comparatively speaking smaller than in a 50.  In my data on chronograping my 54 110 grs of 2f gave 1821 ave.  with a 1/16 touch hole.  When enlarged to .070 I got an ave of 1797.  In a smaller bore would that make more of a difference?  To me if there is extra reliability in a .070 I would rather use it.

DP

[Birddog6]

I use larger vent holes than most, never had an issue with accuracy.    And I believe certain combos shoot better (more accurate) at certain velocities......  If you go with a larger vent, just bump the charge up a tad to get back to that velocity & you are back on track.

On a 40 cal & smaller I use a .070 vent hole. On a 45 & larger I use a .078. Have very reliable ignition with all of them and few misfires. I load with a vent pick in the hole. Usually use a piece of wire with a piece of leather attached to it & wrap it around the open frizzen.  Load the rifle, wiggle the wire & take it out.

Others like real small vent, & no vent pick, some like apples, some like oranges, etc....... Whatever works for you........   

[northmn]

When we talk about loss of accuracy what are we talking about?  A national champion target shooter of whatever discipline has some very strict standards.  Some of the people mentioned for changing out a touch hole are these folks.  They get pretty fussy on the loading bench also.  A typical rondy shooter may prefer to enjoy the events more with a little less hassle.  A deer hunter wants a gun that hits minute of deer and goes bang when he sees one. Our thinking on what is adequate has been polluted with technology.  A good shooter off a bench with a scoped rifle can achieve about one inch groups today with little effort.  We start expecting that.  We also shoot ML's because that is boring after while.  As to the velocity or power loss. I hear people say that RB's kill better than paper energy figures suggest.  Paper energy figures have been inflated with modern weapons till some think a 338 is a pretty good deer rifle.  Accuracy is dependent upon application, but does not require 1" groups at 100 yards for most.  The 94 Winchesters have killed lots of game.  A good one will group maybe 4" at 100 yards.  It's hard for us to really change our thinking to what was good for Granddad because he had no exposure to modern technology.  Anyone ever see a PC Benchrest?  Sorry, got long winded again.

DP

[doug]

      I think the effect of increasing vent size depends on powder charge.  I also think that the resistance to gas escaping probably varies as the square of the velocity of the gas; in other words the higher the powder charge, the higher the escape velocity and the proportionately greater the resistance to it escaping and therefore the loss of velocity decreases

cheers Doug

[hammer]

Hello again guys.  Re my post above taken from  Volume III (Ammunition and Performance) 'Small Arms of the East India Company  1600-1856' by D.F.Harding.    Have been looking through the notes I made from that book and find that in the chapter 'Penetration' the EIC found that, on average, the penetration of the ball through 1" wooden boards actually increased with the enlarging of the touch hole.   
That does seem to me support my conjecture of an enlarged touch hole improving initial ignition and efficient burning of the main charge, at least with their powder and in their muskets and rifles.   Doesn't it?
But then we are talking muzzle loading here and logic is rarely a good basis for argument.  Too many variables.

Peter.

     

[Larry Pletcher]

I'm beginning to think there is an experiment in here somewhere.  My Chambers Lancaster has a WL vent that is as Jim ships it - a drill bit .055 is a slip fit.  My thought would be to carefully work up an accuracy load and chronograph  that load.  Then drill the vent to 1/16" and chronograph again, noting the change if any.  If there is a difference, work up an new accuracy load and then re-chronograph.  We might see the new accuracy load appear at about the same velocity as the earlier load.  If desired one could repeat this process by drilling to .064 and repeating.

My thesis, if one is called for, would be that accuracy loads will appear at about  the same velocities regardless of the vent size.  Please realize that this is not my opinion - I really don't know what will happen.

I haven't run this past my partner in crime.  Steve Chapmen is still at Friendship and can't be reached by cell phone.  His help with sights, methodology and probably shooting will be necessary.  Curious about your thoughts.

Regards,
Pletch

[northmn]

Accuracy is usually credited with being a result of variance in velocity as well as the velocity itself.  When all is said and done it may be easier to replace a vent than to work up a new load for those into tight groups.  Increasing a powder charge lends itself to increased fouling, which may affect the variance.  One thing I have noticed in my chronographing is that the first shot out of a very clean barrel is low.  One does not get a stable string of shots until the barrel is fouled.  Maybe I am shooting too loose a patch ball combination, but target shooters like to foul their barrels.  Another thing I have always felt is that a flintlock seems to like a minimum charge to keep the vent clean. Admittedly a personal observation
That may have no foundation.  Replaced a vent for an individual that tried about 25 grains in a 45 rifle and had the whole charge sputter out the vent without moving the ball much.  That rifle had a large vent.  Yet charges like that work in pistols?

DP

[Dphariss]

These two ideas have been floating around in my mind for some time and i wonder what your opinions are.  These are related to the "Reliability vs Accuracy", but I didn't want to hijack the topic.

First relates to vent size and accuracy.  I talked with Joel Gard (Bevel Bros.) about his opinion about accuracy going south as the vent eroded.  We know that velocity lowers as the vent enlarges - nothing new there.  If the shooters accuracy load  happened to be at 1500 fps, and his larger vent lowers velocity to 1350, perhaps it's a simple matter to increase the load and get back to 1500 fps.  This is probably an over-simplification, but has anyone tried to get back to the accuracy load by increasing velocity rather than swaping out the vent?


The other thought is how we think of the pan charge and the barrel charge.  Normally we think in terms of one charge igniting the other.   This seems normal especially in barrels with a cylinder shaped vent.   But how close do the two charges have to be before we think of them as a single charge?  For instance we install a vent that has a web .025" thick.  If the pan priming is only .025 away from the barrel charge, maybe it's not two charges at all - just one charge.  In my mind if we prime the pan close up against the barrel we really have only one charge that simply extends into the barrel.

Just unproven ideas,
Pletch

Caution. Theories for discussion follow. I do not consider this "fact" but possible factors to consider.
The problem arises when powder is expelled from the vent on loading or as the pressure builds in the barrel. While I cannot prove this is it possible that there is powder, burning surely, expelled. This changes the charge weight at random.
Increasing the charge weight may or may not work since this would bring the velocity up but the ball will start at a different point and/or the increased charge may change the recoil characteristics or the harmonics of the barrel. More variables.

I think the "one charge" idea has merit for the purposes of ignition as I assume you mean it. With FFF powder powder granules my actually protrude from the barrel. However, my Manton style lock has a vent wiper that moves the powder away from the vent about 1/8".  Now I am wondering how it would work without this?

Dan

[chapmans]

   I'm home.
   Steve C.

[Acer Saccharum]

My gut feeling is that you'll get more pressure variation with the larger touch hole. But I like how you are thinking about your test, Larry. That would add some fact to the fiction.

[Larry Pletcher]

Caution. Theories for discussion follow. I do not consider this "fact" but possible factors to consider.
The problem arises when powder is expelled from the vent on loading or as the pressure builds in the barrel. While I cannot prove this is it possible that there is powder, burning surely, expelled. This changes the charge weight at random.
Increasing the charge weight may or may not work since this would bring the velocity up but the ball will start at a different point and/or the increased charge may change the recoil characteristics or the harmonics of the barrel. More variables.

I think the "one charge" idea has merit for the purposes of ignition as I assume you mean it. With FFF powder powder granules my actually protrude from the barrel. However, my Manton style lock has a vent wiper that moves the powder away from the vent about 1/8".  Now I am wondering how it would work without this?

Dan

Dan,
You may be right about the variables regarding charge weight etc.  Probably can't separate that from the differing vent size.  I need to think some more about that.

The "one charge" idea does come from ignition consideration.  As someone mentioned, the barrel charge ignites under pressure while the pan does not.  I was simply thinking of how the flame front travels across that .025" gap.

Steve,
Glad you're home.  You probably read that I opened my big mouth and got us into another one.  We need to talk about some possibilities.

Acer,
Pressure variation you mentioned could very well be another variable.  With some of these, we just won't know until we give it a shot.  (pun intended)

Regards,
Pletch

[Dr. Tim-Boone]

Controlling all the other variables in order to test the hypotheses concerning inner cone vs outer cone and then size of touch hole and then size of charge will require some "guns" to be built with comparable barrels and rifling and that will all need to be able to use the same lock for the tests eh??

 I suppose the trials should be done with both FF and FFF too? 

How good of a proxy is muzzle velocity for barrel pressure? 

In order to have practical value I suppose the barrels would need to be of "typical length of 42" or 44"??

You might need to apply for a grant!!!!   

[Larry Pletcher]

Tim-- You have such a wonderful way of making the project sound simple.   

If we get this figured out, we will need to greatly simplify the methods.  I'd like to use a pristine WL liner in a flint gun set up with good target sights.  In two guns I have in mind, the load would be developed with a patch/ball combination that is already known to produce tight groups.  Starting that way we can try at least to eliminate everything but vent diameter.

I would like to see (for a start) what velocity change  we'd get by going from a .055" vent to a 1/16" vent.  That will give a quick indication if we are on the right track.  Then we'll want to see if we have lost our accuracy sweet spot with the decrease in velocity, and can we get it back by getting back to the original velocity.  We have to keep this as simple as possible.
Regards,
Pletch

[Acer Saccharum]

Sorry if I digress, this is a bit off topic.

. However, my Manton style lock has a vent wiper that moves the powder away from the vent about 1/8".  Now I am wondering how it would work without this?

Dan

Dan, the prime burns with a flame that goes UP and OUT, eventually burning to the bottom of the pile of priming. With the Manton, this gap in the prime almost guarantees the first thing to hit the touchhole is FLAME, not unburnt powder grains. Nor does the flame have to burn down thru the prime to get to the touchhole.

[Acer Saccharum]

Larry, again, I volunteer my machining services, no charge, for anything that you want to build for this.

Is there a pressure transducer we could hook up to the powder chamber that could read chamber pressure? You could not only time the ignition, but see what pressure there is, and WHEN it peaks.

Talk about needing grant money!

[Larry Pletcher]

Larry, again, I volunteer my machining services, no charge, for anything that you want to build for this.

Is there a pressure transducer we could hook up to the powder chamber that could read chamber pressure? You could not only time the ignition, but see what pressure there is, and WHEN it peaks.

Talk about needing grant money!

Acer,
Thank you for your kind offer.  I will remember that as we work.  As to the ability to measure pressure,  I confess to being out of my league on this.  I know it's done, but have no equipment to do it.

If we would choose to try this with my Lancaster, adding target sights would be necessary.  Adding an aperture sight to the front dovetail is no problem.  Adding a good rear apeture without messing up the barrel may be a problem.

If we use Steve Chapman's target rifle, the sight problem is solved.  His rifle is convertible, using a flint or a mule ear.  If we add a WL liner, the percussion nipple won't fit because of the thread change.  Either way we have a hardward problem to solve.  If I could get over the idea of a couple of drilled holes for sights in my Lancaster barrel the problem is solved too.

Regards,
Pletch

[chapmans]

Larry,
  I will drill and tap  the touch hole/nipple to 5/16-24 and Dan could provide the vent liners!!
  I have been wanting to do that anyways.
   Steve

[Larry Pletcher]

Steve,
Let me go through my inventory of 5/16x24 vents and see if I still have one with a .055 vent.  Can't remember what all is down there.    Tried calling you tonight, missed you.
Pletch

[Dphariss]

There is a system, the Oehler 43 that uses transducers on the barrel to give relative pressure. etc etc.

OOPs the Oehler 43 is out of production right now. Just looked.

The cost was pretty high new but its should be possible to find a used one.
But not sure its worth the cost and trouble.

Dan

[Wyoming Mike]

I can only speak from my own experience.  I have had two touch holes burn out on liners.  One was on a .36 that was used for many years and had a large enough touch hole to spray people 25 feet down the line.  The other was a .32 that was my screwup when I didn't drill and tap the touch hole liner deep enough.  When I filed it flush, the web was too thin and burned out on the maiden voyage.

I didn't notice too much drop off in accuracy on the .36 until the touch hole had eroded where it seemed I  was getting a lot of flyers all the time and really spraying.  I was concerned with how much the rifle was spraying out the touch hole more than I like.  I replaced the touch hole and the problems went away.

On the .32 I was putting the first rounds through it and it was shooting well for the first few rounds, then started throwing flyers.  It was also to starting to self prime.  I decided to give it a few more rounds.  After two shots the touch hole burned out too large to even push the ball.  Everything came out the touch hole.  Nothing blew but there was a long phuuut as all the pressure came out the touch hole.  I took it home, pulled the ball and pulled the touch hole liner. 

I found my problem was using the wrong tap.  I used a normal tap on the threads where I should have used a bottom tap.  The normal tap was bottoming out against the barrel wall on the little .32 and I thought I had tapped the full length on the side.  I used a bottom tap and the touch hole liner went into the proper depth and the new liner has worked fine for a couple of years.

In answer to the first theory, the .36 did not shot much drop in accuracy until the touch hole got large enough to give a very noticeably large spray.

As to the second theory, the pan is open and only a small portion of the flash actually enters the barrel so contributes very little, if anything, to the charge sending the ball down the barrel.  By the time the flash contribution is equal to the charge contribution the touch hole would be too large to build pressure behind the ball and go out the touch hole and join the flash.

Just some observations that might not mean much.

I would like to see some data on pressure reduction with size of touch hole though.  That would be interesting.  It does sound like a complex experiment though.