Flash Hole Location and Muzzle Velocity

[Dphariss]

The Nock, rear ignition, apparently gave second place distance according to Greener. This would equate to second best velocity. But this would require modern testing to verify. This is in W. Greener's "The Gun" (not W.W. Greener's later book)

Ignition speed. The Manton recessed breech is reputed to be the fastest. This is what was thought at the time, and apparently why it was produced, since it moves the pan closer to the center of the main charge in the barrel. According to testing the Nock is not fastest in ignition speed.

But increased velocity of one breech over another could reduce lock time if its measured in an actual long gun length barrel with a projectile and check time from trigger pull to projectile clearing the muzzle.

For the average builder the best course is a vent liner/cone that places the powder charge immediately adjacent to the powder in the pan. Vent diameter .060" -.070" should be adequate.
This will provide the fastest, most reliable ignition from pan ignition to ball out the muzzle.
How soon the pan is lit from the time the trigger pull is another variable.
If I were concerned with absolute fastest I would build a 1810-1820 Manton recessed breech lock with a Manton breech to match it. This should test the fastest based on Larry's lock timing.
There is no "trick" the entire lock and breech must be optimised for fast cock speed, sparks right in the pan and a vent/breech that ignites the main charge with minimal delay.
Dan

[Dphariss]

I would think that the dropping of the powder charge and the compression of air during the seating of the projectile would eleminate any flake blocking the ante chamber. I use the vent pick on conventional barrels without the Nock type breech as well.
I think you may have a point about the low quality of powder being a problem in sme cases.

Bob Roller

I dunno.
I shot the gun 5-6 shots with dirty powder and had to trickle powder through the vent to get the thing to fire the last 2-3 shots.
When I got home a light shined down the bore (it shoots a .662 ball and has a 30" barrel) showed a flake of fouling laying over the passage in the breech as I suspected from the experience in the field.
The flakes will fall off the barrel wall with little instigation. If large enough and based on those found in BPCR cases they can be large and surprizingly strog, they will block the passage which I think in this breech is about .173" - .180" in diameter. I think this was occuring before pouring the powder into the barrel.
I suppose if I tipped it muzzle down and bumped the barrel beofre loading this might have been avoided.
I have not bothered to recreate the problem.


Dan

[Dr. Tim-Boone]

Calling Larry Pletcher!!!! This can be tested

[Larry Pletcher]

Calling Larry Pletcher!!!! This can be tested

Hi Tim,
You're right- it can be tested. This came up earlier and I gave thought to doing this.   I thought through the process and came up with the same conclusion that Daryl mentions below. My first thought was that I'd hate to do this to a good barrel; it could be done to a stub, scrap barrel, but running the test with a 12" chunk might yield unreliable results.

Daryl: A barrel clamped down and 3 vent locations, plugged with stoppers and changed out with vents as tested individually would be required to see any difference from vent location. I'd suggest any change might not be worth the effort. I also suggest the logistics of having a vent an inch or so down the barrel will probably cause cleaning problems, and dry-ball problems too. You'd have to pull the plug to get a dry-ball out if the ball got shoved past the vent. It's likely inserting a screw might not get it out as it came past the vent opening as it would/could bind.

Too many problems with different locations - vent at the rear sounds better all the time. It is an interesting scenario for discussion, though.

In the real word of ML shooting, a gun with a forward vent could really be a pain.  Imagine having a gun where the vent was 1" forward of the breech, as Darly mentions.  Make a mistake with your measure and you may see pillow tick when you look into the vent. In any case you now have a barrel that has a minimum load requirement.  You might not shoot a squib load very often, but with this gun couldn't.


Dan: "For the average builder the best course is a vent liner/cone that places the powder charge immediately adjacent to the powder in the pan. Vent diameter .060" -.070" should be adequate.
This will provide the fastest, most reliable ignition from pan ignition to ball out the muzzle.
How soon the pan is lit from the time the trigger pull is another variable.
If I were concerned with absolute fastest I would build a 1810-1820 Manton recessed breech lock with a Manton breech to match it. This should test the fastest based on Larry's lock timing.
There is no "trick" the entire lock and breech must be optimised for fast cock speed, sparks right in the pan and a vent/breech that ignites the main charge with minimal delay. "

I think Dan's summary here is pretty good. I believe that the location of the vent (forward or back) is less important than other considerations:
Is the lock well maintained?
Does it put MANY sparks in the pan?
Is the priming  powder fine grained?
Is some priming powder against the barrel?
Is the vent absolutely clean?
Does the vent allow barrel powder placement "immediately adjacent to the powder in the pan" (Dan)?
(I believe that two charges less than .030" apart ignite like a single charge. Place two charges in a flat surface  .030" apart and try to ignite only one.)

When working with engineering students at the high school, we often remind them that one should concentrate efforts on the things that make the biggest improvements - don't spend time on 1% improvements when you can spend time on 15% improvements.  To apply that thinking to flintlocks, imagine having a really quick chamber/vent liner, use the best priming powder, and then use dull flint.

Getting back to the topic, a test of a forward vent is something that can be done with some adjustments to my equipment if a 10" barrel stub yields the same data as a full length barrel.  That I don't know.  I need to think on this some more... didn't mean to write this much.
Regards,
Pletch

[smylee grouch]

Keep thinking Larry, we all value your imput and look forward to as much as you want to write about it.     Smylee

[Bob Roller]

I have a barrel that is 15/16x26x45 caliber from an underwhacker. Send $10 to me at 1805 Monroe Ave,Huntington WV 25704 to cover USPS and you can drill all the vent you want to, It is in good condition but fits no ideas I have or ever ha d. It has a 1/4x28 nipple thread in it that can be plugged easily and a 3/8x18 breech plug thread (I think).

Bob Roller

[Bob Roller]

FUBAR alert, I meant to write 5/8x18 NOT 3/8.
Bob Roller

[Dr. Tim-Boone]

As an aside.. I just completed a gun with this RE Davis Late English lock and a coned touchhole 1/16" openiing and no liner.  Touch hole is 1/16" in front of the breech plug.



We fired it several time Saturday and it was as fast as a percussion   ... the new owner who hasn't shot BP for 40 years did not flinch or experience any delay... off hand at 25 yards his first shot was dead center and all ensuing shots were touching that hole.... a fowler with only a v in the standing breech for a rear sight.

It is the fastest lock I have ever experienced......so far..

[Dphariss]

Here is something we all need to think about in the front of the charge vent location discussion, aside from those I have already read.
How would you build a gun with a forward vent say 1" or more forward of the breech face, and still have a firearm that looks like the one above in the Logo? Using a trigger release bar similar to a Borchardt or some modern handgun design so the trigger can be in an ergonomic area of the firearm?

While its an interesting philosophical exercise I see no practical application.
I also feel that it may cause excess fouling in the breech. This theoretically could reduce fouling elsewhere I suppose. However, excess fouling in the breech from a long string of shots is how accidents occur.

My opinion is that its fun to talk about but after some thought I don't think I would care to try it. Having no practical application means that the experiment would be simply to prove a theory that has no real application.
I am not that curious I guess.
Dan

[Daryl]

Understandably, Dan.  With normal locks, even a vent mid-charge would throw ergonomics a-kilter.  One of the multi-stacked-charge systems would work for the 'testing' - merely have to build a gun with a sliding lock, complete with trigger.  Instead of having to slide to an entire charge ahead, it would only have to move about 1" total, maybe 1 1/8" total, depending on bore size and charge.
Yes- an exercise to prove a hypothesis.

[Larry Pletcher]

I mulled this over for a day thinking about the merits of doing such an experiment.  In other past experiments, I have felt motivated by the fact that the results might be useful to those who make or shoot flintlocks.  In this case I'm not sure there would be a similar benefit.  I think we'd be beating our heads against the wall of good architecture.

Moving the vent forward 1 inch would play hob with good architecture.  For instance, I have ordered a rifle from Allen Martin, a man whose workmanship I greatly respect.  We have been through all the normal things that a builder and customer would discuss.  Imagine if I went back to Allen and told him I wanted the lock to be moved forward because I wanted the vent to be 1 inch in front of the breech.  I'm sure that Allen's response would be the same as every other fine gunmaker.  He would tell me in very imaginative terms what I should do with that idea. BTW, Allen is the guy who told me at CLA, "Architecture is EVERYTHING!"  I believe that.

So, while a test like this could be done with the barrel that Bob graciously offered, I feel that it would yield no useable information.  As it should, good architecture would rule the day.  Thanks Bob for your kind offer.  I should also say that other ALR members have offered their skills to me when I've contemplated a flint experiment - Acer, Dan Phariss to name a couple.  The help offered and advice available is what makes this such a great forum. Thanks to all.
Regards,
Pletch