General discussion > Black Powder Shooting

Touchhole diameter and accuracy

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cal44walker:
Are the 2 linked? Just wondering if too large a touchole affects accuracy and if so.........why?

Matt

Daryl:
Too large a vent will reduce pressure and therefore reduce velocity.  If the velocity is reduced below the 'accuracy' requirement of the rifle, the accuracy will suffer.

ie; as the vent 'wears out', the pressure and therefore velocity gradually drops.  Not only does group size increase, but the point of impact also changes - up or down or perhaps to one side or the other as the barrel's 'whip' changes and releases the ball at a different 'point' of the whip. Yeah, I'd say they are related for sure.

hanshi:
Hmmm...   I never gave much thought as to the two being related but it makes sense.

Roger Fisher:
Oh Yeah! ::)  After you drill the vent open from a 1/16 with a slightly larger bit and campher the outside just a frog hair and you go happily on down the road and after a good while (less if you use a roughened pick) you notice she is self priming even with 2 f, you will or should notice some low shots.  Thats when you get another liner and start over again.   ::)  By that time a 5/64th will fall in and a 3/32nd darn near!

Been there and done that once or so!

hanshi:
Mine are all still 1/16" and will pass a 1/16" drill bit but not a 5/64".  I plan to take better care of them in the future but have spares just in case.  I occasionally notice a few kernels of 3f come through but so few I can count them.

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