Vented cap lock rifles

[Mowgli Terry]

Vented cap locks: I have a caplock 45 caliber Tennessee rifle that is vented. The vent proper is screwed into the drum at right angles to the bore. The gun could be fifty years old. I may be calling this vent by the wrong name. Doing a search has not given any results to do with cap locks. Is there a real benefit to this vent on a caplock rifle? Should the drum be replaced? Any information is greatly appreciated.

 

[DanL]

Pictures please

 

[Grenadier1758]

The prevailing theory is that the venting allows the heat from the cap ignition to more freely flow into the powder chamber. Early cap lock rifles made by top English gunmakers wanted a vent that emulated the flash hole of a flint lock firearm. The venting was in part due to a concern that increased pressure from the ignition in a more closed powder chamber of a percussion firearm would increase the breech pressure to dangerous levels. In fact, Dixie Gun Works had a "helpful hint" in their catalog describing the venting of a percussion lock by drilling into the drum. The hole was directed away from the face of the shooter.

In practice, the venting was generally of little to no benefit. It does continue in Hot Shot nipples which are vented in the nipple's cone. There is probably more benefit in the slightly enlarged and tapered boring in the cone to the fairly small orifice into the flash channel and the force of the ignition will fragment the cap, making it easier to remove after firing.

I posted yesterday that some shooters (not me) have drilled a vent in the drum cleanout screw or drilled a hole just in front of the nipple in the drum. It acts similar to a hot shot nipple that has a hole drilled into the side of the head of the nipple. Also helps with hammer kickback. I'm not recommending this, but a better place for the hole on this barrel would have been in the cleanout screw. Over 45 years of muzzleloading you see lots of interesting stuff! steg49

Dixie Gun Works used to and likely still does in the technical section of their catalogs discusses install the vents. I have seen the vent holes on original guns (all shotguns I believe) and a even fixed a couple of butchered attempts made by shade tree gunsmiths.

I would plug the hole with the smallest set screw available that works for the current drilled hole. Make sure the set screw doesn’t protrude in the fire channel.

And nothing wrong with using Loctite, the blue (243) and red (263) are rated to 360°F (182°C), a temperature you are not likely to see on a traditional muzzleloader barrel.

This is an image of an 18th century internal touch hole coning tool. Internal coning was known and practiced.

View attachment 238899


The breech plug was removed, and the tool was inserted to turn the bur in the touch hole to make an internal cone.

Touch hole liners were not exactly common on top line English and other Continental rifles, but the gold and platinum liners were known. Touch hole liners do not show up on rifles and fowling guns made in North America. There was a carryover of the liners into the percussion age as it was believed that a vent was needed or the internal pressure from a percussion ignition could burst the barrel. Once it was sufficiently determined that barrels wouldn't burst, the practice of a percussion vent liner was discontinued.

Procedure is still listed in the 2023 DGW catalog. Venting A Percussion Gun found on page 525.

Venting of percussion guns has been discussed several times on the Forum.

 

[oldramrod]

In the early seventies I vented a rifle according to the Dixie Gun works instructions. I found that it did not seem to have any effect, good or bad, I do rub a little beeswax over the vent hole when deer hunting to prevent moisture from entering.

 

[Steve Wagner]

The prevailing theory is that the venting allows the heat from the cap ignition to more freely flow into the powder chamber. Early cap lock rifles made by top English gunmakers wanted a vent that emulated the flash hole of a flint lock firearm. The venting was in part due to a concern that increased pressure from the ignition in a more closed powder chamber of a percussion firearm would increase the breech pressure to dangerous levels. In fact, Dixie Gun Works had a "helpful hint" in their catalog describing the venting of a percussion lock by drilling into the drum. The hole was directed away from the face of the shooter.

In practice, the venting was generally of little to no benefit. It does continue in Hot Shot nipples which are vented in the nipple's cone. There is probably more benefit in the slightly enlarged and tapered boring in the cone to the fairly small orifice into the flash channel and the force of the ignition will fragment the cap, making it easier to remove after firing.






Venting of percussion guns has been discussed several times on the Forum.

Thanks Grenadier. And the vented Hot Shot nipples could be a detriment in some rifles. In my 2, TC Hawkens, they could not ignite t-7, 2f with cci #11s, while the standard TC nipple has no issues with it. Not to be confused with Red Hots [Knight] with no vents, which work extremely well for me. SW

 

[user 34300]

Intuitively, the vent on the drum would let nipple fire go in and out through the powder.

But then again the explosive used in caps is very fast. Some claim a diesel effect lights the powder. The explosion propagates super fast there may not be time for the flame to go around corners and out vents.

IF the powder is under the nipple I can not see how a vent would do anything. The fire from the cap hits coals and you have ignition.

Intuitively I do not see how the vented nipples can do anything for ignition. They might help the hammer to not be blown back to halfcock with a weak mainspring.

 

[Steve Wagner]

Intuitively, the vent on the drum would let nipple fire go in and out through the powder.

But then again the explosive used in caps is very fast. Some claim a diesel effect lights the powder. The explosion propagates super fast there may not be time for the flame to go around corners and out vents.

IF the powder is under the nipple I can not see how a vent would do anything. The fire from the cap hits coals and you have ignition.

Intuitively I do not see how the vented nipples can do anything for ignition. They might help the hammer to not be blown back to halfcock with a weak mainspring.

Agreed Scota. And learning from this forum about this subject, I want my eroded flash hole to tell me when a nipple is worn out. I don't want a vent removing a clear warning sign. I also doubt that, if the powder gets directly under the nipple, the vents in the Hot Shot nipples do anything but let flame and heat escape out of those same vents from the back pressure. That was my immediate thought when they did not work in my TC's.
And if you mean by a "diesel effect" that in correct ignition, the heat from the cap causes spontaneous combustion of the powder before the flame ever gets there, I think this is highly plausible. My mechanic explained to me that if a diesel engine can be cycled until friction raises the internal temperature to 180 degrees, it will start spontaneously. Glow plugs and heat screens just speed this up. There is no spark or flame ever involved. The old bulldozers had a gasoline 'pony' engine just to cycle them until they sputtered to life. A much slower process than a cap, but the principle remains. Spontaneous combustion.
Hope my mechanic got this right or I will surely pay here. SW

 

[Mowgli Terry]

Thanks for answering my question in detail. I plan to leave my vent in place until time the drum can be replaced. There being no benefit discovered over time is, to me, the final word. Should I need to block the vent temporally, there's plenty of hard bullet lube here that will work very well.