vent hole

[Dave Waters]

I looked and I can't find it but has some one done a study on the optimum size of a vent hole? 

[D. Taylor Sapergia]

I have always, until recently, bored out a liner with a #50 drill bit - .070".  But now I only go to .0625" or 1/16".  There's a fine line between instant ignition, and inefficient pressures (accuracy), and rapid wearing out of the vent.

[SCLoyalist]

When I installed a White Lightning vent liner a few months ago, I noticed that the vent was smaller than the 1/16th" that seemed to be the norm.   I was advised that the smaller hole gave more consistent muzzle velocities (i.e. smaller standard deviation) advantageous for target shooting, but drilling it out to 1/16" would give more reliable ignition.   Also, if left at the smaller diameter hole, it would take approximately 3000 shots before the vent became enlarged to more than 1/16" and require replacement.

So, with respect to the question about 'optimum size of a vent hole,' you'd have to qualify how you measure optimum - accuracy, reliability of ignition, service life of the vent, or other.

[Don Getz]

I'm with Taylor here.   I almost always open up my white lightnings to 1/16", just seems to work right............Don

[Larry Pletcher]

Clean is everything IMHO.  I have been using a #51 or #52 bit to allow use of a pipe cleaner if or when necessary.  I believe 1/16" in fine if kept clean.
Regards,
Pletch

[Robert Wolfe]

Without a vent liner I find 1/16" too small but about right with a liner.

[Curt Larsen]

I used 1/16" without liners on my first buiilds and 3/32" once by accident.  They all worked well, but I plan to use white lightnings from here on in.

[bob in the woods]

I use my flintlocks in the field more than at the range. My dedicated target rifle is bored to 1/16th vent.
All of the rest are 5/64  .   The 5/64 vent is pretty close to absolutely reliable

[northmn]

In my hunting guns I use a 49 or 48 wire gauge which is slightly under a 5/64.  I chronographed a 1/16 vent in a 54 and then enlarged it to a .07 or 50 drill bit as they recommended it at that time. There was a small difference in MV in favor of the 1/16 but not much.  Maybe 30-50 fps.   I also have a 25 that has a vent drilled out smaller than 1/16.  My 58, 12 bore and 20 bore have larger vents.  I personally feel that that helps ignition and makes less difference in a larger bore than a smaller bore.  Should test it some time.  Target shooter seem to like the 1/16. 

DP 

[Dave Waters]

I really appreciate all the responses. For years I always used 1/16 (.062) for the vent hole. I too use "White lightin'" liners and drill them out to 1/16 as Don said. On my latest build I happened to measure the WL vent an it was .053 for which SCLoyalist explained Jim's reason. It seems that general consensus is that 1/16 is the best cross between velocity and reliability.

Thanks again.  ---Dave Waters