This is going to be interesting.
To my knowledge there is never been any modern study of breeches and those done in the past were early 19th century or before and were really not anything that could be called scientific today. Larry's work to date is all there is.
The Nock breech, depending on who you read, was supposed to get the shot charge, like most English flintlock improvements it was designed with wingshooting in mind, out the muzzle faster, either from better velocity or faster ignition from cock fall to muzzle. It was also intended to keep the entire powder charge from being "packed" when the gun was loaded. In theory the looser powder in the "antechamber" should ignite faster since it has more airspace between the grains, this should allow a burning grain of powder to ignite grains other than the ones it it in contact with. This *should*increase flame travel through the powder in the antechamber this *should* produce a faster shot. But unpacked powder in the main charge will give wider velocity/pressure variations so having the entire charge loose is not a good idea from this perspective.
At the time some thought that the powder was compressed against the base of the projectile/wad column and being pressed tight burned like a rocket motor as a result.
The Nock breech (1787 patent IIRC) was supposed to limit the powder being compressed at the vent and to shoot a jet of gas into the base of the main charge and this was supposed to burn the powder better and give better velocity.
The recessed breech was developed to get the fire closer to the center of the powder charge and to reduce the width of the gun when building side by side doubles. This was a Joe Manton invention circa 1800 I think.
It was supposed to give faster ignition as well.
The History Channel did a series on "Masters" and one was on Joe Manton. In slow mo video the recessed breech gun got the shot charge out faster than the non-recessed breech. This from the flash in the pan not trigger pull.
But it will take some experimentation to sort all this out.
Since the Nock breech was designed to increase velocity so it may not show much improvement in time from pan flash to charge ignition. Its all a puzzle right now.
I have a recessed breech Manton lock (made from The Rifle Shoppe Castings) on a 16 bore rifle with a 1 3/16" breech barrel. The recess is .150 deep so it moves the powder in the pan closer to the main charge. I made a Nock breech for the gun because I wanted to use all the final developments of the flintlock on the gun.
I made a forged mainspring to replace the faulty casting and rearched the frizzen spring to make it stiffer.
The finished rifle is very fast, the fastest I have every shot. I have speeded up locks in various ways, bending cocks and frizzens etc, over the years and goofed some and had to go back and repair. Usually too light springs. But this lock needed nothing but a carbon steel face on the frizzen.
I do have a rifle with a lock made by a friend using a cock and frizzen he bought. This lock has the late "link" internal mainspring arrangement and has a very fast cock fall. But it is hard on flints (very) and the rifle while fast, is not as fast as the "Manton" rifle. The Manton lock has strong springs but is far easier on flints. This idue to the geometry of the lock. The angle the flint strikes the frizzen and how the frizzen moves as the flint scrapes down its face. The result is a fast lock that sparks well and is easy on flints. This lock hardly needs any flint sharpening, when it starts to miss fire in most cases the flint is shot and sharpening will not bring back the fire for more than a shot or 2.
How much this high tech lock effects the speed remains to be seen.
It is possible that the slightly faster lock and the faster vent and the recessed breech all combine to make a big enough difference in the total ignition time from the break of the sear to bullet out the muzzle that I notice it.
This is more complex than just having the powder flash in the pan and set off the main charge. Some pretty wise people all though the 18th century, at least from the time wingshooting became a sport, well into the 19th spent a lot of effort to improve the speed of the flintlock I am sure some of the stuff was jsut something to increase their name recognition or even get to put something like "Gunmaker to HRH" on the barrel. But some of the stuff worked.
Hopefully with Larry's help we can get some "modern" scientific answers.
I sent of some parts today. I hope they do what I expect for Larry and give us something to get our teeth into.
The comments on why the breeches were made as they were is based on reading various sources. Frankly I do not know exactly what Nock thought he was doing. I suppose reading the patent, if its available, might shed some light. In the time of the flintlock science was pretty much magic for the most part.
In reading W. Greener's "The Gun" from 1835 we find him claiming that allowing the barrels to fly backward under recoil when proved reduced the breech pressure. So when reading old gun books one needs to be careful what he accepts as fact. The things he could measure, like how far a certain breech design would throw a ball with a given powder charge, is probably representative. But a lot of the stuff is basically a guess someone thought about too much.
This is why having Larry do this work is important.
Dan
