vent on caplock rifle?

[tinsmith]

I just finished re-building a muzzle loading .36 caplock rifle. It was a kit gun from several years ago. Must have been his first M/L project. Was an interesting challenge trying to correct the mistakes and finish it right. He probably had over $500 in parts and I bought it at a local pawn shop for $100. Was pleased with the results.

Now my question. On the drum, 90 degrees from the nipple there is a 1/16" hole that must be some kind of vent. I've never seen this before. Why was this done? I could thread it and plug it with something like a 3-48 screw. Should I leave it? Shot it today without any problems and seems very accurate.

[arcticap]

If you look at some of the photos of drums from the Track of the Wolf website, you'll notice that most drums have a hole drilled in them for a clean out screw to be installed.
Some may be threaded and some aren't.--->>> https://www.trackofthewolf.com/Search.aspx?search=drum

I believe that the hole should be plugged, especially if it's designed to have a clean-out screw installed.
That will help to keep hot gases and blow back from exiting, and is a way to help to clean out the flash channel after the nipple is removed.

It's important to apply ant-seize on it's threads and to not let it get rusted in place by cleaning it after every shooting session along with the nipple.

[Tom W.]

I do believe it's where a clean out screw is supposed to be. My T/C doesn't have one, but my Son's CVA does.

[arcticap]

There is a difference between a drum and a bolster or snail.
A snail or bolster like the TC's and Investarms guns have in their design has a smaller clean out screw.

A drum such as on CVA and Traditions guns has a larger clean out screw.

[tinsmith]

Please let me explain further. The drum does have a clean out screw in the end. This tiny (about 1/16") hole is drilled through the side of the drum into just below the nipple and vents forward and up at about a 45 degree angle.
Yes, good advice on the anti-seize. I had one heck of a time removing the clean out screw from a Lyman Great Plains that I purchased at an auction. Finally had to drill it out and re-thread the bolster to a larger size.

[arcticap]

Some theories that I came up with:

1. The designer of the drum may have wanted to help the air escape during ramming the ball which in turn would help powder to flow into the drum and flash channel.
If someone leaves the hammer down and a spent cap on the nipple when they load powder and ram the ball for the next shot, then the air does not escape as easily which the whooshing air can help powder flow into the drum.

2. I guess that it might also help air to escape on the downstroke during swabbing and let air in on the upstroke during swabbing which would help make swabbing easier.
Less chance of losing a patch off of a tight cleaning jag inside the barrel?

3. Perhaps letting air into the drum as the cap is snapped will help to carry the cap flame into the flash channel?

4. Another possibility is that if the hole directly lines up with the nipple, and if it were threaded for a screw, then it would act as a set screw so that the nipple won't
become loose or be able to be removed without first loosening up the set screw.
Since I don't know the exact alignment of the hole, it's hard to figure it out without knowing if a set screw would come into contact with the nipple or not.

Is the hole being blocked by the nipple threads at all or lead into them?
Is the hole being blocked by the clean out screw threads at all or lead into it?
Does the hole totally bypass the nipple threads and lead directly into the empty air space inside the drum and/or flash channel without any interference?

[DIRT Farmer]

There are those who believe that a vent in the drum increases the flame going into the powder by venting the air in the drum during firing. Same as the vented nipples avatable.

[FrontierMuzzleloading]

Yes thats a vent hole. Some say that when the cap goes off, it allows the air pressure to escape and less chance of hang fire. There has been no testing of this theory to my knowledge to back anything up. I personally feel its just another hole for moisture to get into and contaminate your charge.

[Edward]

Yes thats a vent hole. Some say that when the cap goes off, it allows the air pressure to escape and less chance of hang fire. There has been no testing of this theory to my knowledge to back anything up. I personally feel its just another hole for moisture to get into and contaminate your charge.
Johnson 1942 a former member did quite a lot of research on the subject of venting .He actually went and studied a bunch of museum originals and found high end rifles vented for that very reason . As far as moisture being a problem I guess that"s an issue with flint locks too?

[rfd]

i believe the "clean out screw" is actually a safety valve. unlike flintlocks, cap guns are more like grenades. ;)

[arcticap]

Johnson 1942 a former member did quite a lot of research on the subject of venting .He actually went and studied a bunch of museum originals and found high end rifles vented for that very reason . As far as moisture being a problem I guess that"s an issue with flint locks too?

Thanks for the search tip.
I found 2 threads about it including a photo of a vented barrel and some posts about vented drums.
Apparently the Dixie Gun Works catalog once recommended venting the drum in the same way as the OP's.
There's some mixed reaction about doing it.

1. http://castboolits.gunloads.com/showthread.php?167589-picture-of-vented-precussion-rifle&highlight=venting

2. http://castboolits.gunloads.com/showthread.php?167098-venting-a-precussion-combustion-chamber&highlight=venting

[arcticap]

i believe the "clean out screw" is actually a safety valve. unlike flintlocks, cap guns are more like grenades. ;)

Someone in the threads posted above mentioned the TC vented breech plug.
That was the patented breech plug made for the TC Scout rifle and pistol that vented excess gases forward out of holes in the receiver.
There were tiny channels in the breech plug that needed to be lined up by screwing the breech plug all of the way in tightly.
It's interesting that they never continued it with any other breech plugs that I know of..
They probably invented it because the hammer was directly inline with the shooter and they wanted to help prevent any chance of a breech plug blowing out.
IIRC the Scout design was claimed to have only 3 moving parts.
At least some folks didn't like the vented gases enough to complain about it.


I also read that Investarms stopped putting a tiny clean out screw in the bolster of their rifles.
I'm not sure if that small "clean out screw" was part of the TC & Investarms manufacturing process of drilling out part of the flash channel or not.
The TC & Investarms clean out screws were not very user friendly if that was their purpose which led many folks to simply let them rust in place.

[bob208]

years ago it was done in the theory that it relieved pressure and let the cap flash get to the powder. never did see if it did any good.

[taco650]

Please let me explain further. The drum does have a clean out screw in the end. This tiny (about 1/16") hole is drilled through the side of the drum into just below the nipple and vents forward and up at about a 45 degree angle.
Yes, good advice on the anti-seize. I had one heck of a time removing the clean out screw from a Lyman Great Plains that I purchased at an auction. Finally had to drill it out and re-thread the bolster to a larger size.

A picture is worth a thousand words... got one?

[tinsmith]

Thanks for the input! Nice to get a discussion rather than just wonder about something. I scrounged up a Dixie Gun Works catalog and found the photo of a vented caplock in their reference section. That's just what my rifle has!
I've fired it about a dozen times so far. Ignition is great and accuracy is very good without any real load development. I will just be using this .36 for target shooting and not hunting, think I'll just leave it alone and count my blessings. This is my first rifle with a 42" barrel. Wow, that is a hunk of iron to hold out there for offhand shooting! (My regular offhand rifle sports a 36" barrel.)