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Tag: priming powder

Two Hole Vent Test

This test is a long time coming. A couple years ago at CLA, Steve Chapman and I were looking over a flint gun made by Allan Sandy. The vent Allan used had two smaller holes located horizontally. Allan said the vent was internally coned but used two .052″ holes. Allan said he didn’t know whether it was faster or slower than a normal vent. My reply was that I could time it. Allan offered to provide me a vent, and on the way home, Steve and I planned how the vent would be tested.

Time passed with many interruptions in the way. In the meantime Fred Stutzenberger entered the picture. I believe Fred saw the “double-hole vent” on Sandy’s table at the same show that we did. Fred however, was more prompt than we were and published an article on the vent in the August 2014 issue of MuzzleBlasts.

Without great detail, Fred’s article compared Allan’s double-hole vent with a single-hole vent that had the same area as the sum of the two smaller vents. His findings showed that shots fired with the double-hole vent had slightly higher velocities than the single-hole vent even, though the vent area was the same. The “choked-flow principle” (comparing circumference to area) is the likely cause. Fred explains this better than I do; please read the article.

Our testing focused only on ignition speeds. We compared ignition time of the double-hole vent (two .052″ holes) and the single-hole vent (.073″) Both vents have the same area, but vary in their circumferences.

The main question I have is, “If the choked flow principle tends to restrict flow leaving the vent, might it also restrict flow entering the vent, causing slower ignition?”

We used a 10″ barrel stub with a small Siler flint. The test used a double-hole vent with .052 holes and a single-hole vent with a .073 hole. We did 10 trials each and lit the pan with a red hot copper wire. Our reason for this was to prevent a changing flint edge from entering into the test. The single .073 vent was better both in speed and consistency.

Before finishing, we ran 5 trials each in which the pan was ignited by the small Siler. In those trials the single-hole vent was better, but by a smaller margin. None of the trials sounded abnormal to the ear. No matter the range from high to low, human senses could not tell the difference. In fact, Steve tried to guess and was invariably wrong.

Here you see the shield that prevented both photocells from triggering when the pan flashed

Interpreting the results can sometimes be misleading. In this case, I like the single-hole vent. However, I do have two doubts. (1) I have questions about the reliability of a vent as small as .052”. A double-hole vent with larger holes might alter the result. (2) I wonder if the shape of vent’s exterior would change the result.

The included photos show the fixture and the position of the photo cells used in the timing. The photo cell at the pan trigger the start, while the photo cell and the muzzle triggers the stop.

The last pic is a close up of the vent. These holes are .052″. BTW, the stock is a heavily mutilated factory second supplied by Jim Chambers. It was important because it allowed the sear to be struck from below by the plunger. It also allowed us to use a small Siler lock for an earlier test. At that time it allowed three different locks to be tested using the same lock mortice.

To conclude, I’d like to thank Allan Sandy for the chance to time his vent. I feel that this vent type is well worth studying. I’d like to repeat this with a .055” 2 hole vent.

My thanks also to Steve Chapman and Mike Coggeshall for their assistance in the testing.

Of course every experimenter needs a furry assistant

Larry Pletcher, editor

September 21, 2016
Filled Vent Test – Is it Slower?

Filling a flintlock touch hole with priming powder causes a slower ignition. The pan fire has to burn through instead of flash through the vent. Is this “fuse effect” true? Can the difference be measured? Are the “hang fires” experienced by black powder shooters caused by something else? Reporting the answers to these questions is the purpose in this article.

The purpose of this test was to see if there was a measurable delay in ignition when a straight cylinder vent was filled with priming powder. (We did not deal with vent liners in this test.) For the purpose of this experiment I will define this “fuse effect” as an ignition delay caused by the priming powder having to burn its way through the vent to ignite the main charge instead of “flashing” through the vent. I’m personally not fond of the term because it implies that we know what caused the delay. I like the term “hang fire” because it does not suggest a cause.

The test was set up using a fixture we used earlier to time lock ignition speeds. We used a “pistol” with a barrel stub, small Siler lock, and my computer with photo cells “looking” at the pan and barrel muzzle. The barrel is loaded with 30 gr 3fg and a sabot to hold powder in place. The pan is primed, and ignited with a red hot wire to eliminate lock variables. Between firings, the barrel is wiped with two patches, a vent pick used, and compressed air is blown through the vent to insure that the vent is clean. The pan is primed with Null B close to the barrel. The only difference between the two test phases was that the vent was completely empty in one, while in the other, we picked priming powder into the vent until no more would go in.

The barrel used was octagon 7/8” across the flats and was .45 caliber. It had a flat flint-type breech. The vent was a straight cylinder with a 1/16” diameter approximately .21 inches in length. Time starts when the pan photo cell is triggered and stops when the barrel photo cell is triggered. Thus barrel time is included in this test, however this obviously the same for both vent conditions.

We recorded 5 trials for each vent condition. The average time for the clean, empty vent was .028 seconds. The filled vent average was .031 seconds. As you would expect, the slowest time we recorded was in the filled vent phase (.0363). However the fastest time of the day was also in the filled vent phase (.0233). (We also did a single clean vent trial where we banked the prime away from the vent and recorded at time of .067 – more than two times slower than the clean vent average.)

These averages are quite close together. We expected a larger difference because our ears tell us a hang fire has taken place. And, here is the most unusual finding. The fastest time (.0233) we recorded sounded as if it was a hang fire. The slowest time (.0363) recorded sounded like a sharp crack – no hang fire – sounded like a .22 rim fire. This reinforces a belief I have long held that our eyes and ears are terrible tools for judging flint events.

This all makes me wonder what we are really hearing. Maybe our ears send us false information. Consider this: You are three shots into a target and have 3 tens. You shoot the 4th shot and it’s a nine. Sounded fast, but you think it was just you. You shoot the 5th shot, and it has an audible hang. You look through the scope, and no. 5 is back in the 10 ring. Maybe the fourth shot was slow, the fifth shot was fast, and your ears are at fault. With what we learned here, it could be possible. I truly don’t know the answer. Sometimes experiments leave you with more questions than answers. I do know that I trust my ears less than the numbers.

There are so many variables that can cause delays that in most cases it can be impossible to rule out all but one. That was the purpose in our experiment. We wanted to put a number on the amount of delay, if any, caused by packing a cylinder vent with priming powder.

The delays we found were measurable but not large enough to account for the delays we have measured in pan ignition – where the variables were flint edges, priming, particle size, and location of the prime in the pan. I have measured far larger time variations caused by these variations. The other big factor is the delay caused by fouling in the vent. A vent full of priming is one thing, but a vent filled with fouling is quite another. Besides causing huge hang fires, I believe fouled vents are the flint shooter’s biggest cause of failures to fire.

If I were to list the top causes for delays based on my testing they would be:

1. Lack of good spark production from good flint edge

2. Improper priming location in the pan with good priming powder

3. Vent not absolutely clear of fouling.

(A clean vent filled with prime is not a major cause IMHO.)

February 21, 2011
Pan Vent Experiments – An Introduction

[box type=”note” align=”aligncenter” ]Learning how black powder ignites in a flintlock has been a passion of mine for 20 years. In this series of tests we examine the way fire travels from the pan to the barrel. The process involves the use of camera, computers, and a physics interface. What we learn may change the way we think about flintlock tradition.[/box]

Introduction

This series of experiments has evolved into one of greater scope than originally intended. Earlier intentions were to examine the ignition qualities when the position of the vent hole varied up or down in relation to the pan. The methods to investigate included a computer timing procedure used to measure times from a barrel stub and lock plate with a pan attached.

An L&R plate was chosen because the pan was attached. The plate was drilled and attached to a barrel stub with screws. The rear screw is attached to the barrel through a vertical slot in the lock plate. This allows for adjusting the height of the vent hole in relation to the plate.

At the rear of the plate a hole was drilled to provide a pivot point so that the barrel could be rotated to vertical for loading. The barrel is two inches long but is breeched by using a plug with an octagon shape, providing the same dimensions as the barrel.

The computer equipment used included a science interface designed for use in high school physics classes. The hardware was designed and built in the late 80’s. The computer is of similar vintage, but the combination allows measuring time intervals to the nearest 10,000th of a second.

This photo shows the fixture holding the barrel and the photo cells positioned at the pan and muzzle.

Pan Ignition Experiments

The experimentation has been broken into phases. The results of each section will be used in successive testing. The plan is to learn enough to control variables for our final experiment, which will be to the measure and evaluate of different vent locations. Each of the following parts is a link to the actual experiment. Methodologies used will be discussed as well as the experiment and the results.

Part 1 — Black Powder Ignition Characteristics

(Powder on sheets) This phase of testing was suggested to me by Mr. Bill Knight. Its purpose is to identify how the ignition travels across blackpowder exposed to the air as in a flint pan.

Part 2 — Initial Pan Experiments

(Card between barrel and pan) The card test was designed to determine the intensity of the flame at the vent. An index card was cut and pinched between the lock plate and the barrel. The pan was primed in three different positions.

Part 3 — Photography through the muzzle

In this phase I wanted to see if there was a visible difference in the amount of fire traveling through the vent. I used a digital camera to photograph the fire coming through the vent as seen from the muzzle. The camera is aimed to look directly into the barrel muzzle.

Part 4 — Priming Powder https://www.blackpowdermag.com/part-4-priming-powder-amount-by-weight/Amount by Weight

In this part we will examine the amount of priming powder used. Weighed amounts of powder will be timed. Plans call for .5 grains, .75 grains, and 1.0 grains of swiss Null B priming powder.

Part 5 — Timing Powder locations in Pan (Is it better to bank the powder away from the vent?)

The technique is to use photo cells to detect pan ignition and start the time. A second photo cell detects fire at the muzzle of the 2 inch barrel and stops the clock.. The methodology for this phase needed careful thought. Informal trials yielded some times that were out of predictable bounds. I suspect they were caused by an unknown variable, perhaps fouling.

Part 6 — Timing Vent locations (high, medium, low)

This final test will explore the ignition speed when the location of the vent hole is varied vertically. The test will start with the vent centered on the top of the pan. Other tests will be conducted with the vent as low in the pan as one could expect to find and with the vent located well above the pan center line.

April 17, 2008
Part 2 — Initial Pan Experiments

Burn marks on a card help us to determine the intensity of the black powder burn in the flintlock pan. This was a preliminary step to help determine how to prime the pan.

The card test was designed to determine the intensity of the flame at the vent. An index card was cut and pinched between the lock plate and the barrel. The pan was primed in three different positions. The first was banked away from the vent as tradition suggests. The second was to place the powder in the center of the pan. In last position, the powder was placed as close to the vent as possible without touching. The powder was ignited as in the first test.

Photo 1 shows the fixture, barrel, and the index card in place for the first test.

Photo 2 shows the burn marks left on the index card with the priming powder banked to the outer edge of the pan.

Photo 3 shows the burn marks left on the index card with the priming powder placed in the center of the pan.

Photo 4 shows the burn marks left on the index card with the priming powder placed in the pan as close to the vent as possible without covering the vent.

From the first two experiments I am beginning to conclude that is might be best to prime closer to the vent. The next test was designed to gather more information about this possibility.

Pan Vent Experiments — Introduction

Part 1 — Black Powder Ignition Characteristics

Part 3 — Photography through the muzzle

Part 4 — Priming Powder Amount by Weight

Part 5 — Timing Powder locations in Pan

Part 6 — High and Low Vent Experiments

April 11, 2008
Part 3 — Photography through the Muzzle

Comparing the strength of the black powder burn by looking through the barrel muzzle. Here we see that where the black powder is placed in a flintlock pan is crucial.

In this phase I used a digital camera to photograph the fire coming through the vent. The barrel is mounted on a fixture and the camera installed on the tripod. Height was adjusted until the camera looked directly into the muzzle. In this position the barrel in centered in the camera and the pan is to the left. On the right side of the barrel directly opposite the vent is a cleanout hole. (The cleanout is important as you view the photos.)

The pan was primed with .5 grain of Swiss Null B priming powder in three pan positions: banked to the outside, close to the vent, and as close as possible without blocking the vent. The pan powder was carefully positioned using a pencil with a round eraser. Since the eraser was the same shape as the pan bottom, this worked very well.

The camera was set to have the shutter open for 4 seconds. Once the pan was primed, the procedure was to fire the camera and then ignite the pan. The pan was ignited as earlier with a red hot copper wire. (There is NO barrel powder used until the last phase.)

Photo 1 shows the muzzle shot taken with .5 gr of Swiss Null B priming powder banked away from the vent.

Photo 2 shows the muzzle shot taken with .5 gr of Swiss Null B priming powder positioned close to the vent.

Photo 3 shows the muzzle shot taken with .5 gr of Swiss Null B priming powder positioned as close to the vent as possible without covering it.

Examination of the photos add evidence for stronger ignition with closer placement of the pan powder. Comparing the photos showing the close position and the “banked away” position shows a clearly stronger fire in the barrel and also traveling through the cleanout hole on the far side. While evidence continues to support a close priming of the pan, only timing of the positions will provide conclusive proof. That comes next.

Pan Vent Experiments — Introduction

Part 1 — Black Powder Ignition Characteristics

Part 2 — Initial Pan Experiments

Part 4 — Priming Powder Amount by Weight

Part 5 — Timing Powder locations in Pan

Part 6 — High and Low Vent Experiments

April 8, 2008
Part 4 — Priming Powder Amount by Weight

Determining the amount of black powder to be used in testing. Since flintlock pans are of different size, I felt that this was a necessary step in our process.

In this phase of testing I timed different amounts of priming powder. Ten amounts each of .5 grains, .75 grains, and 1.0 grains of Swiss Null B priming powder were weighed to the nearest tenth of a grain. These were timed in the fixture to see if varying the amount of prime affects the speed or consistency.

The fixture allowed the barrel to be rotated to vertical to load 15 grains of Swiss fffg for the barrel powder. The barrel was then rotated to level and the pan primed. Photo cells were checked to make sure they are pointed at the pan and the muzzle. The last step was to make sure the computer was ready. The pan was ignited with a hot copper wire and the readings recorded. The barrel was wiped between trials.

Photos of the fixture are shown below.

These two fixture photos also show the range of movement that can be used to test the location of the vent hole in relation to the pan. The top photo shows the hole in it’s lowest location, while the bottom photo shows highest location. For all tests so far, the vent hole has been centered on a line level with the top of the pan.

The graph below shows the trials with the three different priming powder amounts:

In evaluating the results of this test, I found Joe Sharber to be of great help. Joe, a fellow blackpowder fan with statistical experience, provided help with the number crunching. He pointed out that there is no statistically significant difference in the average ignition times. However he also noted that the variability or standard deviation was statistically significant.

Joe suggested that the term “Coefficient of Variation” * may be of value as a measure of consistency. The CV listed in the chart helps to show the advantage in consistency of the trials done with .75 grain priming powder. Because of this .75 grain will be the powder amount used in future tests.

* Coeficient of Variation is defined as 100 x (standard deviation divided by the mean). It is given as a percent. My thanks to Mr. Sharber for his assistance.

Pan Vent Experiments — Introduction

Part 1 — Black Powder Ignition Characteristics

Part 2 — Initial Pan Experiments

Part 3 — Photography through the muzzle

Part 5 — Timing Powder locations in Pan

Part 6 — High and Low Vent Experiments

April 4, 2008
Part 5 — Timing Powder locations in Pan

Is it better to bank the black powder priming away from the vent? This piece of conventional flintlock wisdom will be tested.

Part 5 of our test series will examine the question about where in the pan provides the best ignition. Conventional wisdom has told us that banking the priming powder away from the vent will produce the fastest ignition. Practically avery black powder shooter has heard this. This theory is based on human senses or what looks and sounds fast. The current test is designed to see if conventional wisdom is correct.

Early attempts showed a trend developing but had results that did not fit the rest of the range. A careful plan was developed to remove as many variables as possible especially those that were caused by fouling. Between firings the following were done:

The barrel was wiped. An additional step was added here and explained in the video.

A pan brush was used.

A pipe cleaner was used in the vent.

Compressed air was blown into the vent.

The priming powder used was Swiss Null B weighed on a balance scales. Since earlier testing showed its consistency, .75 gr was used. Because the placement of priming powder was the variable, care was used in its placement. The charge was poured into the pan and moved into the test positions using pencil with a rounded eraser. Powder could be pushed to the outer edge of the pan as well as very close to the vent. In both of these positions I felt that I was using more care in the powder placement than the normal firing of the lock in the gun. I realized that I chose the extremes in powder placement, and that a shooter would fall somewhere in between.

The tests were run in a 24 hour period with temperature controlled by thermostat. The day was picked with humidity in mind. The humidity varied within a range from 60 – 66 %. This is noted on the spreadsheets. Each battery of tests consisted of ten trials each – prime banked away from the vent, and prime placed as close to the vent as possible without covering it. To insure that no priming method had a unfair advantage, the trials were alternated so that a complete test battery included 10 trials each, alternated for a total of 20 trials.

At the end of the test session the ten trials for each priming method were recorded and all parts cleaned. Battery 1 was done in the afternoon at 60% humidity. Battery 2 was done in the evening at 66% humidity. The final battery was done the following morning at 60% humidity.

I made a short video that showed the processes involved:

The results are shown in the spreadsheet below.

The obvious conclusion is that banking the prime away from the vent doesn’t produce the most rapid ignition as we once thought. Banking the powder way from the vent actually reduced the ignition speed by 16%. This conclusion runs counter to conventional wisdom heard for years in muzzle loading circles. However, it is consistent with earlier tests where we saw photos with brighter fire from a close positioning of the prime.

While these results change the way I will prime my flintlock, there are other considerations that must be dealt with. In my tests the pan was ignited by a copper wire heated red hot. In the real flint world the sparks need a bed of powder on which to land, and this must be part of or priming procedure. This means that when I prime my locks, my emphasis will be close to the vent rather than away from it, but the bottom of the pan must have sufficient prime for sparks to land in. Thus, how well a lock places its sparks in the pan becomes an equally important consideration.

One other result of this experiment is that I have become increasingly skeptical of human senses in how I perceive flintlock ignition. And, there are more questions. What about low vent locations? This has always been rejected as a cause of slow ignition. Maybe we’re wrong about that as well. We’ll look at that in Part 6.

Pan Vent Experiments — Introduction

Part 1 — Black Powder Ignition Characteristics

Part 2 — Initial Pan Experiments

Part 3 — Photography through the muzzle

Part 4 — Priming Powder Amount by Weight

Part 6 — High and Low Vent Experiments

April 2, 2008