Touch Hole size

[oldarcher]

I am trying to determine what is the ideal size for a touch hole, and if bore size has any bearing on the touch hole size. I currently drill a .075 hole for the touch hole to get a good quick ignition in .40 to .58 cal. Would any one be kind enough to advise the actual size that they are using? Thank you

[Daryl]

My flinters all start at 1/16". I find good ignition at that size and have Taylor re-vent with a new White Lightning opened to 1/16"(.0625?) after they get to about .075".
When vents become too large, they become self priming and/or blow much of the charge out the vent when seating a ball.

[Boompa]

I've been using a #51, (.0670), bit with good success. It's just a tad larger than 1/16" @ .0625

[wattlebuster]

Mine seem to do just fine at 1/16th

[David R. Pennington]

On my last few rifles I've used 1/16 and cone inside with Tom Snyder's neat little tool. Very quick ignition. My old .50 had a stainless liner that finally burned out and my groups started opening up. I pulled the old liner and made a new one and it's back to normal.

[hanshi]

I started from the beginning drilling mine out to 1/16"; ignition is fast and reliable.  I still get a small amount of self priming using 3F but I have to look to notice.  I also remove the new liners and  open up the inside cones a little more.

[L. Akers]

Years ago I noticed that when I replaced a burned-out liner with a new one, my ignition was very noticeably faster.  I reasoned that happened because all the fire and pressure that came out the enlarged hole is now staying in the breach igniting  more powder.  If that is true (I reasoned) a smaller hole would keep even more fire and pressure in the gun where it belongs.  I experimented with hole size, starting at .052.  I got an unacceptable amount of misfires so increased to .055.  Better, but still an unacceptable amount of flashes.  My magic number was .059.  I get no misfires and the guns I build have extremely fast ignition.  I'm ready to change liners by the time they burn out to .062!

[hammer]

I have this theory/suspicion/belief that the perfect hole size is closely related to the grain size of the main charge.    The finer the grain, the smaller the hole.    The larger the grain, the wider the hole. 

In the early 19th Century the East India Company studied touch hole size in the Brown Bess musket.   They found, with their musket powder, that the larger the hole the quicker the ignition and the more efficiently the powder burned.    More reliable ignition and consistent pressures.   Till it became too much of a risk to the adjacent soldier in the line.    The musket powder of that time in the English army was of very high quality.   They were looking primarily at reliable ignition with an already primed pan.   So any main charge dribbling from the touch hole was not a factor.   

At the other end of the scale we have quality sporting fowlers with finer grain sporting powders, again of the highest quality and likely better than the very best today, with tiny, coned holes in platinum or gold liners.   Famed for their reliability and ultra fast lock time. 

My suggestion is that a smaller grain will more easily ignite and more quicker burn and can do so with a weaker initiation from the priming charge occasioned by a smaller hole.    Conversly a larger grain is less easily ignited and slower to burn and will require a stronger initiation provided by a wider hole.   On this theory I have opened up my touch holes till just a few grains of the of the chosen main charge will consistently pass through the touch hole into the pan.   

[oldarcher]

Thank you for the information.
Hammer, what size touch hole do you usually end up with?

[rhbrink]

I agree 100% with L. Akers and Hammer makes sense too at least in my experience.

[oldarcher]

Thank you all for the information...after reading I pulled the WL touch hole liner and installed a new one and drilled it to .060 about (1/16) I plan to go to the range next Sat and check it out..
One other thing that happened was when I went to the tool box I discovered that all of the Easy Outs that I had were either damaged or broken so a trip to Home Depot was in order. Instead of the traditional Easy Outs that I have used for many, many years I bought a Ryobi "Spiral Screw Extractor Set". These extractors are much more tightly threaded and looked like they would grab the part to be removed very strongly. You use them exactly like you use an Easy Out. I put the barrel in the vice on the mill and drilled out an appropriately sized hole and then chucked the Screw Extractor in the mill and dropped the extractor to the WL touch hole liner and backed the touch hole liner without any difficulty at all. They actually work great, much better than the older style Easy Out. I am very conservative in tool selection and am very slow to make changes in what has worked for years....But this was a great choice and I wanted to pass this along to everyone.
 

[bgf]

1/16 or a hair under seems ideal with 3f. I think accuracy falls off when it gets much bigger, and elevation change is obvious after some time.  My experience is like above, just a little too small a hole causes lags and flashes.

I left the last touchhole in my offhand rifle way too long last time...  Shot 2f for a while as stopgap--that helped for a while. Made a big difference when I changed it out!

I check by putting 1/16" drill shank into hole.  If it's tight or at least no wiggle, it's ok for offhand.  A little tighter for chunk gun.

[smylee grouch]

Interesting read Hammer. My hunting rifle is about 20 years old and never had the WL liner replaced. I am one of those who pics the vent with a stiff wire before every shot so the hole has probably been wore and eroded larger over the years. Last year when Bear hunting I forgot to bring my 4f prime flask and had to use the regular powder ( 1 & 1/2 Swiss ) to prime. When I took my shot it went off as fast as I could ever remember it going off.