I built a 45 cal. percussion rifle with drum and nipple but never comfortable with strength in the breach area of the drum and nipple system. Will venting the drum at the clean out screw (8/32 screw) with a 1/16" hole lessen the breach pressure? My goal is to improve the safety level when using loads of 60 - 80 grains of Pyrodex. Also, will the rifle's performance be affected by the vent hole. Yes, I am aware that anyone standing to my right side must be advised of the flash.
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Venting drum on percussion
- Thread starter rfcbuf
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paulvallandigham
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I had a .45 with a weak mainspring, that let the hammer lift up enough to allow the caps to come off the nipple after firing, sometimes, getting totally loose. I used a 1/64" bit- the smallest bit I could buy, and drilled a hole through the cnter of the clean out screw in the end of the drum. It turned out to be the same diameter as the screw slot in the screw. That took care of the problem, and vented gas and smoke, to the side, like the vent on a flintlock, instead of towards the muzzle where it could burn fingers if I didn't hold the gun exactly right. I did have to warn other shooters not to stand to the right of the gun when I fired, but that was not a hard thing to do. I also found I needed to plug the hole with a little grease- bore butter worked- to keep moisture out of the main charge. When I did this, the gases sent that little plug out of the gun about 4 feet, so I had to make sure people were not standing too close, or go to the end of the firing line to shoot.
Some due drill a hole in the drum in front of the nipple to vent gases up and forward. That works fine if you never shoot with your forward hand brought back close to the breech, and have long fingers that wrap around the stock. You can get a sever burn to a finger or two if you forget where those gases are going.
As to relieving pressure, the size of the whole will dictate how much pressure is relieved. Most .45 cal. guns can be shot using much less powder than 65 grains, which is getting up near the max for most barrels. You velocity is getting close to 2000 fps with that much powder, and that is just not needed for normal round ball shooting. That kind of load is done by the chunk gun shooters, and they are generally shooting much stouter built guns. Either switch to using FFg powder, or back that charge down to 50-55 grains of FFFg powder. You will stress the gun much less keeping the velocity within limits. Just my $.02 . Other opinions will vary.
Some due drill a hole in the drum in front of the nipple to vent gases up and forward. That works fine if you never shoot with your forward hand brought back close to the breech, and have long fingers that wrap around the stock. You can get a sever burn to a finger or two if you forget where those gases are going.
As to relieving pressure, the size of the whole will dictate how much pressure is relieved. Most .45 cal. guns can be shot using much less powder than 65 grains, which is getting up near the max for most barrels. You velocity is getting close to 2000 fps with that much powder, and that is just not needed for normal round ball shooting. That kind of load is done by the chunk gun shooters, and they are generally shooting much stouter built guns. Either switch to using FFg powder, or back that charge down to 50-55 grains of FFFg powder. You will stress the gun much less keeping the velocity within limits. Just my $.02 . Other opinions will vary.
George Holton
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I once saw a drum protruding from a mans arm.It came from the gun on his left and was followed by the whole lock. The shooter had spilled powder into the drum to prime a damp load. apparently powder had sifted inside the lock mortice nd a loose cap did the job. It waas a piece of manure gun from a big box store.
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I saw in my Cains Outdoor catalog (www.cainsoutdoor.com) thay have replacement drums for about every rifle with a cleanout screw already installed in the end of the drum. The cleanout screw on my hawken I had years ago rusted shut in the hole and never could be removed.
Ohio Rusty
Ohio Rusty
If your concerned about pressures, use a smaller powder load. IMO, the small difference that a vent hole in your clean out screw, or in the drum for that matter, will produce isn't worth the effort of putting it in.
I have drilled a 1/16 inch diameter hole in the drum of several CVA rifles, between the nipple and the barrel and angled slightly upward and forward but this was to improve the reliability of ignition with Pyrodex, not to reduce pressures. (Yes, it seemed to help).
I own a number of rifles which use a unvented side mounted drum and I have no concern about the safety or pressures at all.
If the threads in the barrel and on the drum are full threads, there should be no danger.
I say this based on the following:
The surface area of a 5/16 inch thread (fairly common for the drum to barrel threads) is .0767 square inches. A 90 grain FFFg powder load under a 245 grain Lyman Maxi slug will produce about 18,900 PSI breech pressure.
That much pressure acting on the area of the drums threads will create a force of 1450 pounds.
A 5/16-18 mild steel nut (basically the same as the tapped threads in the barrel) is easily capable of operating at a load of over 3300 pounds which is over twice as much load as the above slug/powder load will create.
By the way, the pressures for a .440 dia roundball with a 90 grain FFFg powder load (which IMO is a very "hot" load in a .45 cal gun)are about 16,200 PSI which will exert a force of 1242 pounds of force on the drums threads.
zonie
Pressures from Lyman Black Powder Handbook & Loading Manual
I have drilled a 1/16 inch diameter hole in the drum of several CVA rifles, between the nipple and the barrel and angled slightly upward and forward but this was to improve the reliability of ignition with Pyrodex, not to reduce pressures. (Yes, it seemed to help).
I own a number of rifles which use a unvented side mounted drum and I have no concern about the safety or pressures at all.
If the threads in the barrel and on the drum are full threads, there should be no danger.
I say this based on the following:
The surface area of a 5/16 inch thread (fairly common for the drum to barrel threads) is .0767 square inches. A 90 grain FFFg powder load under a 245 grain Lyman Maxi slug will produce about 18,900 PSI breech pressure.
That much pressure acting on the area of the drums threads will create a force of 1450 pounds.
A 5/16-18 mild steel nut (basically the same as the tapped threads in the barrel) is easily capable of operating at a load of over 3300 pounds which is over twice as much load as the above slug/powder load will create.
By the way, the pressures for a .440 dia roundball with a 90 grain FFFg powder load (which IMO is a very "hot" load in a .45 cal gun)are about 16,200 PSI which will exert a force of 1242 pounds of force on the drums threads.
zonie
Pressures from Lyman Black Powder Handbook & Loading Manual
Many Klatch
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My wife has a .36 percussion with a drum. We were having a terrible time with the fire channel gunking up during a shoot. One old timer recommended that I take a #52 drill and drill a hole right through the clean out screw. It works.
I don't think that I would drill the hole in the drum to reduce pressure. The advantage is that the firechannel keeps a lot cleaner than otherwise.
Course, now that she has her flintlock, the percussion sits unused.
Many Klatch
I don't think that I would drill the hole in the drum to reduce pressure. The advantage is that the firechannel keeps a lot cleaner than otherwise.
Course, now that she has her flintlock, the percussion sits unused.
Many Klatch
mothernatureson
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I have always used Uncle Mikes Hot shot nipples, they are vented . they work great , and improve ignition and hammer blow back on very stout hunting loads.
IMO, the vented nipple does give the powder gas another way out, and in doing so it usually causes the cap to fragment making removal very easy.
It also provides an air vent in case the shooter forgets to remove the cap and put the hammer on half cock before loading his next shot. (By having the nipple hole clear when loading, the loose powder is blown back towards the nipple when loading. This helps prevent hang-fires and mis-fires).
I think the location of the vent in a vented nipple is too close to the cap to do what the "vented drum" is supposed to do.
Venting the drum is supposed to reduce the gas pressure between the cap and the bore of the gun.
This should help the caps flame get to the powder better than in a gun without the vent.
The only guns I did this to were two CVA rifles which seemed to be having problems with igniting Pyrodex and it seemed to help.
Because I now shoot Black Powder, I have not seen a need to vent the drums on my current Percussion guns.
zonie
It also provides an air vent in case the shooter forgets to remove the cap and put the hammer on half cock before loading his next shot. (By having the nipple hole clear when loading, the loose powder is blown back towards the nipple when loading. This helps prevent hang-fires and mis-fires).
I think the location of the vent in a vented nipple is too close to the cap to do what the "vented drum" is supposed to do.
Venting the drum is supposed to reduce the gas pressure between the cap and the bore of the gun.
This should help the caps flame get to the powder better than in a gun without the vent.
The only guns I did this to were two CVA rifles which seemed to be having problems with igniting Pyrodex and it seemed to help.
Because I now shoot Black Powder, I have not seen a need to vent the drums on my current Percussion guns.
zonie
I have an ancient .58 percussion buscheflinte (side by side rifle/shotgun) from Saxony with platinum-plug vents below the nipple with no drum. The vent holes are not much larger than a human hair. Someone on an internet thread said this arrangement had pretty much disappeared by about 1835, so it looks like vents are back.
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