Drilling out flash hole, Results!

[Fly103]

I have been reading alot about drilling out pedersoli flash hole liners to larger sizes. I measured mine on my Penn. rifle and found it to be .055", I drilled it out with a #50 bit to .070" and fired about 30 shots. There is definitely a perceptible difference in lock time, before I could audibly hear the click of the frizzen opening a fraction of a second before the boom, now it seems instantaneous. I wasnt complaining before but now she's as fast as greased lightning.

Just thought I would share for any pedersoli owners considering doing the same.

Chris

 

[Grenadier1758]

@Fly103, this is valuable information for all flintlock users, not just Pedersoli users. One should use the smallest touch hole that gives excellent ignition of the main charge. Most liners will start out at a small dimension such as 0.055" or a #54 number drill. Most of us will find that we need to open the flash hole to 0.062" or 1/16". And sometimes using the number drills to get to the #50 at 0.070" is the best choice. The maximum I recommend opening the touch hole is 5/64" (0.078"). Most of us only have a fractional set of drill bits so the two sizes available are the 1/16 or 5/64. There are 5 number drills between 1/16 and 5/64.

54​	0.055​
53​	0.0595​
1/16	0.0625​
52	0.0635​
51​	0.0670​
50​	0.0700​
49​	0.0730​
48​	0.0760​
5/64	0.0781​

 

[waksupi]

The larger the vent, the larger your groups.

 

[ohio ramrod]

If my memory is right. The Bevel Brothers ran some serious tests about ten years ago(or so) and found that 1/16 gave the best firing time using high speed cameras , before groups enlarged. And eliminated "flash in the pan" with out firing the main charge. Above 1/16 did not do much to improve time but did enlarge groups.Now if I could just get my flints knapped to get sparks I would shoot my flints more than my percusions.

 

[NorthFork]

@Grenadier1758

That is an excellent chart for future reference. Thanks!

 

[Nameless Hunter]

@Fly103, this is valuable information for all flintlock users, not just Pedersoli users. One should use the smallest touch hole that gives excellent ignition of the main charge. Most liners will start out at a small dimension such as 0.055" or a #54 number drill. Most of us will find that we need to open the flash hole to 0.062" or 1/16". And sometimes using the number drills to get to the #50 at 0.070" is the best choice. The maximum I recommend opening the touch hole is 5/64" (0.078"). Most of us only have a fractional set of drill bits so the two sizes available are the 1/16 or 5/64. There are 5 number drills between 1/16 and 5/64.

54​	0.055​
53​	0.0595​
1/16	0.0625​
52	0.0635​
51​	0.0670​
50​	0.0700​
49​	0.0730​
48​	0.0760​
5/64	0.0781​

And if you want to split the difference, there's always metric drill bits from McMaster Carr:
1.45mm = 0.057"
1.55mm = 0.061"
1.65mm = 0.065"

 

[Fly103]

Ohio Ranrod, it would be nice to know if they accounted for pedersoli's goofy patent breech? Since I only shoot offhand I think the much faster lock time probably improves my offand accuracy far more than a slightly oversize flash hole hurts it.

The flas hole in my pedersoli harpers ferry was enlarged to .098 by the previous owner and it is definitely too large. The powder seems to fuse instead of flash and when the charge ignites there is a large fwoooooosh! From the flash hole. Velocity is so low even with 40gr that the .570 ball wont penetrate a .25" plywood sheet at 25yds.

Chris

 

[excess650]

IIRC, TC liners are .070" and sometimes dribble fffg. I prefer smaller that that, and my quickest is smaller than 1/16".

 

[Sidney Smith]

I always open up new flash hole liners to 1/16th. The holes they come with are definitely too small.

 

[Bob McBride]

All mine get popped to 1/16” straightaway.

 

[Daveboone]

I have a new Pedersoli (Lyman) GPR flinter. My first flintlock. I certainly had a noticeable lag on ignition with the original, and having read about enlarging it I bought both a 1/16 and a 5/64th. The plan was to see how the 1/16 worked first. After I drilled the flash hole out, being a perfectionist I decided to take the 5/64 bit and gently debur the outside of the whole. Wrong. Those liners are much softer metal than I anticipated! To make the story shorter, I ended up drilling it out to the larger whole all together, so I never had a chance to see how the 1/16th would work. That said, ignition was now instantaneous. I was pleased, but several other flintlock shooters at my local club commented on it being about the fastest ignition they had seen/heard. I agree with them it can be mistaken for a caplock. I havent had the opportunity to see how the groups changed with the jump from a bench, but they sure as heck have to be tighter just with the greatly decr. fire time.

 

[flntlokr]

I always drill my liners to 1/16, and countersink the inner end of the hole to leave the narrowest parallel-sided 'throat' possible, in order to create a venturi, which causes the flame to constrict and compress and thereby increases the speed of the flash into the powder charge. I get good, fast ignition with only rare misfires. (I make my own liners from set screws)

 

[Sidney Smith]

I always drill my liners to 1/16, and countersink the inner end of the hole to leave the narrowest parallel-sided 'throat' possible, in order to create a venturi, which causes the flame to constrict and compress and thereby increases the speed of the flash into the powder charge. I get good, fast ignition with only rare misfires. (I make my own liners from set screws)

If you buy those liners with the hex tool slot on the outside, you wont have to countersink anything. It will already be done for you.

 

[Professor flintlock]

I have some berilium bolts that I made liners from. One is over ten years old hasn't burnt out yet . Coned them on the inside with about .040 thick on the out side. . Drilled them two sizes smaller than 1/16. Every one thinks it sounds like a percussion gun. Very few pan flashes very reliable. They are filed flat on the outside removing the screw slot. I always pick the vent before I shoot..055 for the size.

 

[Professor flintlock]

I have some berilium bolts that I made liners from. One is over ten years old hasn't burnt out yet . Coned them on the inside with about .040 thick on the out side. . Drilled them two sizes smaller than 1/16. Every one thinks it sounds like a percussion gun. Very few pan flashes very reliable. They are filed flat on the outside removing the screw slot. I always pick the vent before I shoot..055 for the size.

Oh yeh the hex liners are trash. Never seen one that was reliable.

 

[olskool]

now i will show my ignorance, why will the group size increase if the flash hole is larger?

 

[Mulebrain]

now i will show my ignorance, why will the group size increase if the flash hole is larger?

I would assume by decreasing the pressure of the main charge

 

[thompson50]

The larger the vent, the larger your groups.

Why is that?

 

[olskool]

I would assume by decreasing the pressure of the main charge

why? that little bit of pressure loss i think would be of so little consequence it would not make any noticeable difference,,,,,,,,,,,,

 

[M. De Land]

now i will show my ignorance, why will the group size increase if the flash hole is larger?

The reason is because of the uniformity of ignition shot to shot. The same is true of brisinance in modern cartridges. Different primers and flash hole uniformity in brass cases effect accuracy and is the reason they are tried out for group size. The same thing is happening with flint lock ignition . The diameter that makes the most reliable and consistent flash migration to the main charge will be the most accurate all other considerations for accuracy being met as well.