2 vents, one liner

[bob in the woods]

Since we seem to be on the subject of vents, I thought I'd ask if there was an advantage to having 2 vents….I saw this on a
British fowling gun and wondered if it might be a good thing to have on a gun that requires the utmost reliability ?
Anyone familiar with this?

[elk killer]

back in the early 80s when Oregon Trail Rilfesmiths was in business
we experimented with 2 touch holes on a Leman style rifle
found it wasnt much of advantage
one seems to works just as well if not better
just didnt work out as well

[Virginiarifleman]

More than two holes in one barrel worries me.

[galudwig]

Fred Stutzenberger talks about "2-holers" in the August issue of "Muzzle Blasts."  After some limited experimentation, he found an average of 3.2% in crease in velocity from a two-hole insert compared to the one-holer.  He also measured the amount of powder lost through the touch hole during loading and noted that more powder was lost through the single hole liner than the two-holer.  He acknowledges that his data set is limited, but surmises that the velocity increase could be attributed to a) something called the "choked flow" phenomenon, to b) to less powder being forced out of the two-hole liner, or perhaps c) a cumulative affect of the two.  

I'm no engineer, but the "choked flow" principle has something to do with the effect friction plays on the speed gas will pass through an orifice.  While his liners had the same cross sectional areas (0.0042 square inches), the hole diameters were 0.078 for the single hole liner and 0.055 for each hole in the two hole liner.  You have to read the article to get the full understanding, but I assume that may mean that the hot combustion gas passed through two small holes at a (relatively) slower speed that it did through one (slightly larger) hole; resulting in slightly more velocity at the muzzle.  

Interesting concept.  However, if it were truly a significant advantage in everyday shooting, I would think that you would see more "two-holers" on the line or in the woods.  Seems like hair-splitting to me.  I think ignition from a well tuned flintlock with a single hole liner is pretty darn fast to begin with.  Most (like me) could benefit more from concentrating on sight picture, trigger squeeze, and follow through and not be too overly concerned about a 10 or 15 fps gain in velocity.  It's as if we're trying to get the ball down the barrel as fast as possible before we flinch instead taking the necessary steps to ensure that we don't.

[Top Jaw]

I didnt read the article yet, but has anyone used a second vent to achieve a better position in relation to the pan?  (As in - if your vent is too low or too high).  I have one rifle with a very high vent.  It doesnt seem overly slow to fire, but I have never tried to fire it in the rain, where it might be more of an issue, as the frizzen just does cover it.  I have toyed with the idea of drilling s second lower hole in the vent liner.  Of course this might fall under the category of dont fix a problem that isnt one,....and come in out of the rain!    

[galudwig]

Here is a related thread you may want to look at:

http://americanlongrifles.org/forum/index.php?topic=24140.0

While it does not address your question about drilling a second, lower touch hole, it does get into experimentation Larry Pletcher has conducted on vent position and powder position in the pan.

Here is one of "Pletch's" posts in that thread that kind of makes me think that you might have a problem not needing a fix:

Wade,
The high vs low vent test is in Part 6:

http://www.blackpowdermag.com/featured-articles/part-6-high-and-low-vent-experiments.php

I should mention that the testing I did was two fold.
1.  I wanted to test the old idea that banking the priming powder away would help ignition speed.  I found this to be false.  The closer the priming,  the faster the ignition.

2.  I wanted to test the high vs low vent locations.  Before this, I would have gone with tradition and thought the higher (level with pan) vent would be faster and that a covered vent would be even slower.  This came, as it often does, with discussions at Friendship. I was in Mark Silver's booth listening to Mark and Gary Brumfield.  Gary related that he and Wallace had recently seen originals with very low vent locations - too low to be accidental. I told him that that could be tested.

The result was that I timed a level, low, and high position. And also timed these positions with priming close to the vent, middle of pan, and banked away from vent.  My gut now says that regardless where the vent is, I want the priming very close to the vent, in fact against the barrel. In the low vent test the priming covered the vent, however I did not attempt to fill the vent.

BTW, my thinking is that hang fires are not caused by a vent filled with powder.  A vent filled with fouling is quite another story..



While you're at it, make sure to read Pletch's BlackPowderMag article rferenced in the link.  Definitely worth the price of admission!