Blow out hole on percussion guns

Discussion in 'Percussion Rifles' started by Col. Batguano, May 7, 2019.

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  1. May 19, 2019 #61

    Kansas Kid

    Kansas Kid

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    They sure are some fine looking pieces.
     
  2. Jun 1, 2019 #62

    Redleaf

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    BlackHillsBob knows what he is talking about. Years ago when I first heard of this I was skeptical too, but after trying it, I could see the difference like night and day. I had two caplocks then, both with drums. I vented through the cleanout screw. Not only did the "spatBoom" ignition turn into just BOOM, but I quit having fouling problems in those drums. That was 30 something years ago and I have vented all the cap guns I have built or bought since then and a dozen or more others for friends. I know half a dozen other serious target shooters who would never consider "not venting" a cap gun. The ignition and fouling difference can be profound in some guns. In all the guns I have had my hands on and all those I know of that belong to other shooters, I have never heard of venting a caplock causing a problem.
     
  3. Jun 4, 2019 #63

    52Bore

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    Here’s an early one from the 1830’s.
    B3335B44-3E42-4388-B6E3-ECF79138D9F1.jpeg
     
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  4. Jun 4, 2019 #64

    fleener

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    dont you know inlines are not allowed?

    Fleener
     
  5. Jun 4, 2019 #65

    Zonie

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    IMO, traditional guns made before 1865 seem to fit the forum even if the cap isn't in the usual place so I'm leaving 52Bores picture in the topic.

    If that picture was of a modern inline barrel, it would be gone.
     
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  6. Jun 5, 2019 #66

    fleener

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    Zonie

    The problem with communicating over the internet...I was not serious about it being thrown out. Just making a point that inlines are not a terrible thing to be shunned.

    Sorry

    Fleener
     
  7. Jun 5, 2019 #67

    lamarkeiko

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    When I read this thread, I felt I should give my experience with the blowout hole.
    I purchased my first black powder rifle in 1968. I still have it, and it is an original German Jager rifle made in 1848 by GF Stormer. Attached it a picture of the lock and breech area showing it's blowout hole. Several years later I scratch built my first black powder rifle, a Hawken using a little book "The Way We Did It" by Bud Brown. I don't know where I came up with the idea to add the blowout hole, but my original had one, so I copied it. I figured it was doing it's job, and I went to my first black powder rendezvous in 1976. The firing line was close quarters and the person to my right was getting some good powder burns on his neck coming from my blow out hole. When I went home after the rendezvous, I drilled and tapped out the hole and put in a set screw. That has been over 40 years ago, and I have done a lot of hunting and shooting with that gun since, and I don't think I have ever had a miss fire. I also built several rifles after that first one and never put in the blowout hole. 20190604_173015.jpg 20190604_173049.jpg 20190604_173149.jpg
     
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  8. Jun 6, 2019 #68

    Woodnbow

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    Beautiful rifles there...
     
  9. Jun 12, 2019 #69

    Rokon

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    I believe the concept is a carryover from the flintlocks which obviously had a vented barrel and were loaded with heavier charges than the percussions that followed. I can understand a builder making this decision during the transitional period from flintlocks to percussions.
     
  10. Jun 12, 2019 #70

    Nativearizonan

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    It is surprising to me how many folks think they know more about how a percussion system works than the people at Purdey in 1840 did. I think they knew what they were doing, even if we don't understand why. I totally defer to them and trust there was, at the time, a good reason for why they did it, as they spared no expense in making the finest firearms available.

    That does not necessarily mean the reason still exists. It may well have been negated by other advances in such things as quality of powder and or percussion caps; nipple design, and such. So I won't rule those possibilities out. A vent may have made a big difference in 1840, but not so much by 1870.

    For those that say there is still an improvement by venting, I see the displacement of cold air as the most likely reason. While the charge is still seated in the gun, there is cold air between the percussion cap and the powder; how much varies with the system. A mule-ear or under hammer would have less than a bolster, a bolster may have less air space than a drum; for example. This cold air is what might insulate the contact of the flash from the cap with the powder. The cold air in this space can compress, along with whatever air is in the voids between powder grains, to work satisfactorily; but perhaps it may not always do so; and this could also vary with different powder quality and size. If the cold air fails to compress enough, I can see how ignition could actually be prevented, especially if the hammer spring was weak enough to allow the hot flash to escape through the nipple. Another problem that could allow the hot flash to escape might be too large of a hole in the nipple itself. The vent, however, would allow the cold air to escape. It being located further down, and at a point, in the drum, where mixing of flash with cold air would be taking place. This escape of cold air, in turn, would prevent compression of cold air from possibly hampering ignition of the powder. It sounds quite rational and logical to me.
     
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  11. Jun 14, 2019 #71

    52Bore

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    Shot 2 rounds of Sporting Clays 40 shots total at the NMLRA Spring National, noticed air coming out of hole onto my leg when loading until the end of shooting.
    This now might give some insight as air coming out the vent hole during loading may have been a thought in the early 1800’s.

    Photo and closeup of my leg by the ML on the loading bench.
    3B0722EB-8869-4BF5-B362-18FD50452EFE.jpeg
    33545B7C-90B5-4064-BD12-40FC0B7CCFCE.jpeg
     
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  12. Jun 14, 2019 #72

    Kansas Kid

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    I would probably rather hear the air coming out the nipple so I know it’s open.
     
  13. Jul 6, 2019 #73

    willi

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    Hello, about one year ago I bought this Austrian Rifle and wondering a lot about the small venthole at the side of the drum...thought it may act like a safety valve. All my fellow ML shooters believe also in this. We all, only guessing and no one came up with another idea.
    So today I got the correct information and it make sense to me, thanks to everyone on this Forum and on this matter. Try to upload some picture for give you guys a view..
    with my best regards to all American ML, who keep shooting and hunting with muzzleloader a life.
    Willi
     

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  14. Jul 6, 2019 #74

    Feltwad

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    That vent hole on your rifle is way too big it has got that way through been constant firing in that condition for a vast number of years and now it is dangerous A vent hole is so small it only allows a small amount of air to enter the fire channel to assist firing from the cap and quick the ignition, it should never allow a blow back ,you have lost a large amount of pressure before the bullet has left the muzzle .If you want my advise have a proper small one fitted and you will find that your gun will shoot better
    Feltwad
     
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  15. Jul 6, 2019 #75

    willi

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    Hello Feltwad, thanks for your advise, my feeling was also that this venthole is a bit to big, after seeing the pictures, only I don't know better and because the whole Gun was in quite excellent condition, I thought, this is maybe the way it have to be. So what's about .015 or .020 ?
    Thanks and regards Willi
     
  16. Jul 6, 2019 #76

    sealgaire

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    Both the priming compound in the percussion cap and the BP, of course, are explosives. They do not need Oxygen from the air to react. In fact, air mixed with either will interfere with the quickness of the reaction. When a percussion cap explodes, it is not the priming chemical igniting the BP, but the heat from the reaction reaching the BP, in the form of heated air. With no blow out hole that air is compressed and actually rises in temperature. If there is a vent the air is not compressed as much and the temp of the air reaching the BP is not as high. Also, as the air is compressed the molecules are closer together, collide more often and transfer the heat faster.

    I do not know the history of why the early makers of percussion guns included these vents, but understanding the chemistry and gas laws it does not make sense to include one in a modern percussion rifle.
     
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  17. Jul 7, 2019 #77

    willi

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    Your explanation make some sense too..
    Only I guess we talk about milliseconds in Ingnition time and now, I m thinking about the purpose again, why they did it ?
    Was it for overpressure safety, or avoid that the was Hammer thrown back, or for making sure the the channel is free and unblocked after the shot ?
    Feltwad said, if the vent hole is too big, it can lead to a lost of pressure before the bullet leave the muzzle and this maybe affecting the shooting groups. What I think this is true, if the pressure lost is different from shot to shot ! So, what to do ? Make it smaller, or block it ?
    Sorry for my english writing abilities, don’t put it on a gold scale as we have this saying in German. This forum is a treasure chest for me and I appreciate the way, you Americans keeping the traditional Muzzleloading shooting and hunting alive. Thanks and regards. Willi
     
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  18. Jul 7, 2019 #78

    Grenadier1758

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    The touch hole for a flint lock rifle is 0.062" in diameter. The vent in Willi's rifle id 0.028" in diameter. While he is showing a lot of flame out of the vent, I doubt that he is seeing much of a loss of pressure. Those vents in percussion guns are seen on the better and best quality guns. Since most of these are platinum, the intent was to provide a smooth path for the heat of the cap firing to be carried by the expanding gas generated as the cap exploded. The platinum vent was also a very visible indication that the gun maker was doing something extra to make the firearm more reliable. These platinum vents are seen on European guns in far greater frequency than on guns made in America. It would seem that if the vent provided a path for the compressed gas to the powder, then the vent near the drum would be carrying heat away from the charge. I have not seen such vents on rifles made by the Hawken brothers or many of the other makers of plains rifles and certainly not in those rifles made for the trade. The blow out hole may provide some benefit in reliability, but it will take scientific measurements to verify and most of us will never see improvement other than the belief that if there is a vent then performance is improved. I do believe there is anecdotal evidence of improvement. I don't see the need to vent my barrels.
     
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  19. Jul 7, 2019 #79

    lyman54

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    I always cock the hammer back to leave the nipple as a vent when reloading, otherwise it seems harder to make sure the ball is seated properly. Some say it's dangerous as embers may be present. Don't know about that but having a ball not seated properly is more so I would think.
     
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  20. Jul 7, 2019 #80

    willi

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    So, I just leave the diameter of the vent hole, like it is and trust the Gunmaker. The flame out of the vent hole and at the Muzzle looks more dramatic in the picture than with the naked eye. I also switch to Swiss #3 and instead of #2 (55 grains) and vent and muzzle flash are nearly not visible anymore at the daytime ...I may need to check it in the dark, for seeing the different ...Thank you and regards. Willi
     
    Last edited by a moderator: Jul 7, 2019
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