percussion drum venting

[lanedh]

In another post, Paul V. refers to drilling a very small hole in the cleanout screw in a percussion drum. I am curious to know if any of the brothers here have purposely drilled into the drum to vent trapped air when loading. Somebody once advised me to drill a small hole radially into the drum, pointing diagonally upward (like about 2 o'clock when looking end-on to the drum), ie. about 90 degrees displaced from the nipple. It is supposed to encourage powder to migrate from the bore to beneath the flame from the cap.

Anybody?

 

[JOHN L. HINNANT]

Good Morning Bluejacket,

Venting is usually done to try to solve an ignition job.

Theorically, the back pressure created from the ignition of the main powder charge is supposed to blow out residue build-up in the flash hole between the bottom of the nipple and the powder charge.

The back pressure IS SUPPOSED to lift the hammer slightly and vent through the nipple. Well.... depending on the caliber and powder charge, maybe it does..... or maybe not.

Some rifles seem to suffer more from this build-up of residue than others. If you have a rifle that is having an ignition problem, venting might or might not solve the problem.

Should you wish to vent your drum, it is best to drill the end of the breech. In this way, the full length of the drum will be cleared by the back pressure of the ignited powder charge.

Of course, there is a disadvantage to any shooter standing to to the vent side of the drum; getting splattered by vented gasses. You really should warn them of that possiblity; unless, of course, you have a reason for splattering somebody (that is a joke;..... I think).

In a number of cases, the flash hole diameter inside the drum, between the end of the nipple and the powder charge is much too small and cause fouling residue to build up very quickly.

If SAFETY POSSIBLE, sometimes this part of the drum can be drilled out to a larger diameter. BUT, DO NOT, drill past or through the diameter threaded for the nipple.

The better designed drums have a larger diameter flash hole than the diameter where the nipple hole is threaded.

Should you decide to vent your drum, be aware that eventually the vent hole wil be eroded to a larger diameter, which can introduce another problem in terms of accuracy.

It is for this reason, my personel perference is to istall a vented clean-out screw in the end of the drum. When the clean-out screw is eroded out beyond use, it can be replaced without the need to replace a vented drum.

Patten breech nipples seem to have more than their share of this problem also.

When Rabbett03 built his TOTW Jim Bridger Hawken, he was overwhelmed with fouling and complete blockage of the flash hole in less than 5-6 shots.

We solved the major problem, but still had to vent the snail to get reliable and consistent ignition. There is still one more correction that can be done, but requires removing the breech from the barrel.

Since Toney's problem, I have been studying modern patten breeches of all makes and have come to a definate personal opinion about a certain aspect of todays patten breech design.

Many of the breeches have a shallow or short depth poder chamber with the flash hole drilled at an angle straight to the bottom of the nipple.

This is supposed to promote faster ignition.

When one measues the length of the flash hole from the end of the powder chamber to the bottom of the nipple, it become readily apparent this is a very long distance for the primer flash to travel up a small diameter hole to the powder charge.

Depending on the make of the breech plug, the flash hole length varies from 3/4" - 1". No wonder fouling builds up and blocks the flash hole.

Due to safety, the flash hole can only be drilled out to a slightly larger diameter (which was done on Rabbet03's Hawken), but not enough to make a significant difference, without venting the snail.

The best solution, where possible, is to drill the powder chamber deeper, thus shortening the length of the flash hole. However, drilling the powder chamber deeper is also limited because of the flash hole coming into the powder chamber at an angle.

Drill the powder chamber too deep, and the flash hole enters the side of the powder instead of the back of the the powder chamber. Will this make an accuracy difference? I do not know at this point.

My old 1981 vintage Santa Fe Hawken rifle (which has been a platform for several different barrels)
has the older, more traditional powder chamber/flash hole design, does not require venting, and has never had an ignition problem.

The powder chamber is drilled to a depth nearly equal to the length of the threaded breech plug tenon. The flash hole is drilled at a right (90 degrees) angle from the back end of the powder chamber to intersect the bottom of the threaded nipple hole at a right angle.

The flash hole length is just slightly less than 3/16" long.

When I machined my stainless steel breach, the same design was used.

Neither rifle nor any of my other Hawkens with the right angle, short length flash hole has ever had an ignition problem or required venting.

I am also one of those shooters who wipe the barrel between each round. Any fouling that is theorically pushed into the powder chamber has no effect on ignition.

And one last observation. In my opinion, the powder chamber diameter of least one of these patten breeches is too small and would benefit from being drilled out to a larger diameter as well as being deepened

Hope this information will prove useful to you Bluejacket.

Best regards and good shooting,

John L. Hinnant

If you are not an NRA or NMLRA Member, why not? I am carrying your load.

 

[davy]

Does anyone have images of these particular powderchamber designs? Please I mean "specifically" to these guns ... not generic powder chamber pictures ... :hatsoff:

Davy

 

[Many Klatch]

We drilled a touch hole into the end of the drum on my wifes .34 rifle to help the drum keep cleaner during shooting. I used a #52 drill. We figured that the crud that built up in the drum would blow out the touch hole. It seems to work.

Many Klatch

 

[Blizzard of '93]

DON'T DRILL UNTIL YOU HAVE SONE INFO FROM VERY KNOWLEDGEABLE PEOPLE. !! I HAVE NEVER HAD TO DO THAT, IF YOUR HAMMER IS JUMPING BACK - USE LESS POWDER.

 

[Zonie]

Bluejacket: I believe John Hinnant covered about all of the bases, but here's my thoughts for what their worth.

The idea of venting the drum as you describe, ie, at the 2:00 position between the nipple and the barrel isn't so much to vent the area while your loading (although it does).
The thought is that when the cap fires, it is trying to blow it's flame into a plugged or dead-headed area at the breech of the barrel. By providing a vent right next to the barrel, the flame will be able to easily travel that far which will put it within about 1/4 inch of the main powder charge. Any loose powder that is blown back thru the flame channel towards the nipple will be 'right in the line of fire' so to speak.

I did this venting to a couple of side drum CVA rifles (a Fronter and a Hawken) that had very poor ignition when using Pyrodex. It did improve the reliability quite a bit.

I should add here that I own a number of side drum style percussion rifles and I have not had ignition problems that would cause me to consider this venting method on any of them.

IMO, if you do not have a cap (or fragments of a cap) on the nipple, and the hammer is at half cock when you are ramming the patched ball, the hole thru the nipple will provide enough venting to allow the loose powder to blow back into the fire channel for quick ignition.

zonie

 

[JOHN L. HINNANT]

Greetings All,

I discovered a mistake in the language or terminology in my text that might cause some confusion.

In paragraph 5, that statement,......"it is best to drill the end of the breech" is incorrect.

That should read,......"it is best to drill the end of the DRUM".

My apologies for a slip and misuse of terminology.

Zonie's post covers some excellant points, and he is quite correct in his thoughts.

The Hot Shot nipple with vent holes drilled through the side of the nipple has gone a long way in eliminating the need to vent the breech. Since their inception, they have been my No. 1 choice in percusion nipples.

By the way, Blizzard, high speed photos from many years back show that a 50 caliber rifle loaded with 50 grains of 2FF DuPont Black Powder will lift the percussion hammer about 1/32".

A tight, strong main spring can eliminate most of this hammer lift, but not necessarily stop all of it. A really strong main spring has it own set of problems relating to accurate offhand shooting. A weak main spring has, more than once, been the cause for hammer lift during shooting.

Set back of the hammer is not always an idication of too heavy powder charge.

Best regards and good shooting,

John L. Hinnant

If you are not an NRA or NMLRA Member, why not? I am carrying your load.

 

[paulvallandigham]

I agree with john's comments. A heavy mainspring goes a long way to beating down those nipples, and there is no reason to do that. Certainly all that tension is not needed to ignite the percussion cap. Its best to use either the Hot Shot nipples to vent gases to stop hammer lift, or do as I did a year before the Hot Shot nipples became available, and drill a 1/64" hole in the middle of the cleanout screw. You will have to warn anyone standing on that side of the gun to step back to avoid getting blasted with gases, lube, and other debris, but flintlock shooters are used to that courtesy already. To keep your powder dry while hunting, just put a dab of lube into the hole to keep humidity and rain out of the drum and chamber. The lube will be shot out of the hole by escaping gases, so you will have to re-grease the hole if you mis your shot, and have to reload the gun to continue your hunt. It really is not all that much of an inconvenience.

 

[Runner]

This is the end of a drum out of a CVA Hawken. The bottom of the powder chamber is shown, with a short straight hole in the breechplug leading to that. The hole in the end, the flash channel is too small for the threads on the jag to fit. I am not an expert on breeches, but the CVA leaves something to be desired. The same system leading into a coned breechplug is about as good as it gets supposedly.

 

[JOHN L. HINNANT]

Good Evening All,

Runner, that is an excellant photo and as per the old adage, is worth a thousand words. It clarifies a number of questions that have been posted on the ML Forum.

To begin. Unless I am mistaken, that part is the touch hole liner for a CVA Flintlock. The drum on the percussion model is of similar design.

It is easy to see and explain how both the flint lock touch hole liner and the percussion drum are threaded through the right side of the barrel AND through the side of the breech plug threads into the powder chamber of the the breech plug.

This design feature locks the breech plug solidly into place.

BEFORE the breech plug can be removed, the touch hole liner and/or the percussion drum must be removed. Little imagination is required to understand the problems created if one tries to remove the breech without FIRST removing the flintlock touch hole liner and/or the percussion drum.

The blind hole in the threaded portion of the liner is supposed to line up with the back of the powder chamber in the breech plug. Well..... that is the idea anyway.

Davy's flintlock Pedesoli has a very similar arrangement, and we were able to greatly improvethe reliability of the ignition of that one.

Davy, at our little "ShootinFest" last week, did you have any ignition problems? I was a bit busy and was not paying any attention to your end of the line.

The CVA ignition can be safely improved with a bit of simple machining work.

I will explain this tomorrow, but need to head for the bed now. All of the chickens have long been put to bed, and it is way past my bed time.

Best regards and good shooting,

John L. Hinnant

If you are not an NRA or NMLRA Member, why not? I am carrying your load.

 

[Runner]

John, that is a percussion drum. I parted the rest of the drum off for a barrel I am planning to convert to flint. I also plan to cone the plug if I can ever get it out. I am very much interested in relibility/speed of ignition mods, so I look forward to your posting!

It is way past chickens and almost thru coyote time here.

 

[George Holton]

Just a note in passing, drilling a hole in the drum will really suprise the left hand flint shooter that cozys up to you on your right side, they get a taste of their own and back off to another spot . of course no gentelman flinter would ever do such a thing, and you rember to shoot on the right end of the line. This ok Zonie? Bob
'
'

 

[Mad Monk]

Paul,

This thing about drum venting was something I addressed with my Aussie buddy about 20 years ago.

I had looked at an original percussion rifle at Chuck's one day. It had a tiny hole drilled in the drum. The hole pointed down and to the front. Venting downwards but away from the trigger towards the front.

My buddy in Australia looked at a number of original English ml percussion rifles and noted a vent hole in a number of those rifles.

Going back to the introduction of percussion ignition.
When the percussion system first came into use the number of barrel failures seemed to increase according to some of the writings I have looked at. The theory at the time was that with the percussion ignition you got more powder burning before the projectile had a chance to move and therefor the percussion system gave higher initial pressures in the gun.

There is a chance that the tiny vent holes were first used to mimic the vent in a flintlock and prevent the barrels from failing.

 

[JOHN L. HINNANT]

Good Morning Runner,

This is one mornings that reminds me of an old saying My Dad used to admonish my brothers and me with.

"When you hoot with the owls all night, it is
hard to soar with the eagles in the morning".

Well....Runner, you certainly fooled me into thinking that photo was of a CVA flint lock liner.
Very nice job of modification.

For those members who have asked about converting a caplock to flint lock or flint to caplock, the photo gives a definate illustration of the interior design of the percussion drum or flint lock liner.

Davy's Pedersoli flint lock has a very similar breech design, that we modified two or three years back.

If he should read this, maybe he will re-post those photos here for all to see.

Runner, if you are having trouble pulling the breech plug, try squirting Kroil down the barrel and around the area where you removed the drum.

Kroil is the best penatrating oil I have ever used.

Unless CVA has changed the internal design of the breech plug over the past 25 years, the patent breech powder chamber is very small, about 1/4" in diameter. (I have not worked on a CVA in at least 10 years).

Davy's Pedersoli's breech was designed the same way. In that case, the powder chamber diamter was 1/4" in diameter. Because of the small diameter of the breech plug threads used in the 13/16's size barrel, we could only re-drill the powder chamber to a 5/16's diameter. It was however enough to solve the ignition problem.

Should you be able to remove your breech plug and find it uses a larger breech plug thread diameter, you will be able to safely drill the powder chamber to a larger diameter.

I am thinking that when I made this modifications some years back , the CVA breech plug threads were of a much larger diameter than the Pedersoli.
Right now, I could not swear to that.

Be all of that as it may, drill the the powder chamber to the largest SAFE diameter allowable.

For this job, I prefer to use my lathe to hold the breech while drilling with a Jacobs Chuck held in the tailstock.

In order to hold the breech plug in the three-jaw lathe chuck with a minimum of fuss, I have made up up a series of threaded collars to match the threads of various breech plugs.

The O.D. should be at least 1-1/4" in diameter. This size allows holding of breeches with a cast in snail, such as the Hawken type and up to 1-1/8" size.

It is necessary to make up the collar and breech plug snuggly in order to prevent the breech plug from backing out of the collar during the drilling operation. Be sure to grease the threads before tightening the collar on the breech.

The collars were also machined on my lathe in order to maintain cocentricity of the O.D. AND I.D. These collars are also quite useful when fitting a new new breech plug/barrel together, and the leading thread of the breech plug needs to be relieved in order to fit up to the bottom the barrel threads.

While I prefer to use my lathe for this job, there is no reason why one cannot do this procedure with an electric hand drill, holding the breech plug in a vise.

Of course, it goes without saying, that one must have a steady hand and use great discretion, step drilling in small increments.

Hold All of the horses!

My Sound and Fury is calling for me to do some mundane house-hold chore.

Will be back later.

Best regards and good shooting,

John L. Hinnant

If you are not an NRA or NMLRA Member, why not? I am carrying your load.

 

[Runner]

Apologize for the off topic branch of this thread guys!

This is what I am planning John. The liner is a Tradition's for the DeerHunter flintlock. It is not dirty! That is BB and I don't know why it looks like powder fouling!
Once the original drum is cut down short enough to get the liner even with the side of the barrel, I will use the liner screw slot to put the entire assemly back into the breechplug and tighten it. If I get the plug out, I am going to cone it on the lathe. I already know the ignition is good to very good thru that type liner. If I get the plug coned the ignition should be very good! Luckily, the channel in the original seems to be the perfect size to cut threads in for the liner already. The original will be short enough that the liner will be firing directly into the bottom of the powder chamber.

 

[paulvallandigham]

MM: I knew a fellow who did drill a very small vent hole in the top front of his drum, directing gases forward. He made the mistake-- just once-- of bringing his left hand back on the forestock when off-hand shooting, and the vented gases burned/cut the tip of his wedding finger badly.

On my gun I always made sure that no one was standing to the right of the gun when I fired, for at leat 6 feet. When I asked one man to step back for his own safety until I fired my shot, he stood and watched. After seeing the long stream of gases coming out that vent--easily two feet-- He said, " I guess I owe you my thanks. I see what you why you warned me!" He then asked me why I had drilled the vent, and I showed him how my hammer now caught or kept the spent primer on the top of the nipple instead of it flying all over.

The Hot Shot Nipple is a better idea. I was shooting FFFg powder in that .45 cal. gun at the time, because, like many people here, I found it left less residue, and I was trying to get away with NOT cleaning between shots. But, there is also no doubt that FFFg was generating more chamber pressure than if I had been using FFg powder. If I have a gun like that again, I will play with FFg and a chronograph to see which would deliver a lower SDV, FFg or FFFg powder, and clean between shots, as I do now.

 

[Mad Monk]

Paul,

With my Lyman .50 cal. Trade Rifle I opted to vent the nipple.

I tried a commercial vented nipple that had two small holes that were covered by the cap before firing.

I played with venting my own nipples. Looked at two vent holes versus one. The chrono data showed more shot to shot deviation with the two hole nipple versus the one hole nipple.

That was around the time I looked at different brands of percussion caps to see how they altered velocities.

In 1998 I was forced to switch to the percussion Trade Rifle to match what the plant in Brazil was using to test powder. We had sent balls, patches and lube down to the plant. The only thing we could not get to the plant were percussion caps. The caps in Brazil were corrosive primed. I think they were a perchlorate type percussion cap. Those caps gave velocities consistently 100 fps above what I could get with CCI #11 Magnum caps.

In switching from flint to percussion in powder testing I had to look at what sort of variables you have to deal with in a percussion gun versus the "soft" ignition with a flintlock. In percussion the two big variables proved to be the nipple design and what sort of caps one uses.

 

[Runner]

Several years back I experimented with drilling the nipple out to a larger size to help with ignition. I was successful for a while, but the nipples would rapidly burn out. When they did, accuracy would go to heck in a hurry. How is venting any different in the accuracy department? It would seem that a little venting might be good, but a little too much and you would hit the same sitution as you have with a burnt out nipple venting too much or causing erratic pressures.

 

[Mad Monk]

The way it looked to me was that a single small vent assisted ignition and accuracy but when I went to two holes it acted the same as when the vent in a flinter gets too large.

 

[walruskid1]

paul, i shredded a fingertip with a vented drum on a chunk gun. watch where the fingers end up! :nono: