Author Topic: Flash Hole Location and Muzzle Velocity (Read 13292 times)

Joe S · « **on:** January 16, 2012, 11:00:18 PM »

It seems to be axiomatic that the preferred location of the flash hole is as far back on the powder charge it as possible to place it. I’m wondering if there are any data that would support this idea.

For gas in an enclosed container, pressure on the wall is the same at every point. While this is true of static conditions, I don’t know if is true in the case of firing a gun. If it is true, then flash hole location wouldn’t matter.

If the goal was to maximize the burn rate of the powder, in order to attain the highest possible peak pressure, it would seem that the optional location for the flash hole would be at the center of the powder charge.

Any thoughts?

Roger Fisher · « **Reply #1 on:** January 16, 2012, 11:04:55 PM »

Boy that would make the lock placement look a bit 'funny'

Frizzen · « **Reply #2 on:** January 17, 2012, 12:35:42 AM »

You making fun of my pistol again?

William Worth · « **Reply #3 on:** January 17, 2012, 01:00:47 AM »

It would seem to me like powder forward of the vent can all start moving forward upon ignition ~ whereas ~ powder aft of the vent would have no place to go and would spike pressure in the breech.

smylee grouch · « **Reply #4 on:** January 17, 2012, 02:18:13 AM »

If your vent is forward of the face of the breech it makes cleaning more dificult in my opinion and can also catch patching as you clean. Smylee

Roger Fisher · « **Reply #5 on:** January 17, 2012, 02:34:26 AM »

Quote from: Frizzen on January 17, 2012, 12:35:42 AM

You making fun of my pistol again?

Wouldn't dare.

Daryl · « **Reply #6 on:** January 17, 2012, 02:41:36 AM »

Front ignition has been experimented with modern guns - easier than with a muzzlelaoder as the powder charge and ignition is more easily controled.

Much advantage has been claimed for frontal ignition. Experiments with both chronographs and pressure measuring machines were also made for middle, rear as in normal and front. The last data I've seen on this, done in the 90's, was inconclusive- sometimes better, sometimes the same, somethings not as good for frontal - ergo, the same for rear ignition.

Balisticians say that pressure works equally in all directions. Logic would suggest that more comes out the vent than is projected against the barrel beside the vent or the ball or bullet, yet they say no. Good enough for me. THEY have the machines & can test pressure against the barrel any where they want, breech, sides, bottom, top, etc. Where pressure can be effected, is straight back, but it takes a container like a ctg. case to effect this & one of special shape. In a ML, there is no case, therefore pressure works in all directions equally- according to what passes for modern science on that subject, today.

Joe S · « **Reply #7 on:** January 17, 2012, 05:27:05 PM »

Thank you Daryl. That was exactly the information I was looking for. If the pressure is isotropic, then the world is as should be, and vent location will have no effect on muzzle velocity. These data also suggest that a flat faced breech plug will perform identically to a concave faced breech plug.

roundball · « **Reply #8 on:** January 17, 2012, 05:40:55 PM »

Quote from: Joe S on January 16, 2012, 11:00:18 PM

If the goal was to maximize the burn rate of the powder, in order to attain the highest possible peak pressure, it would seem that the optional location for the flash hole would be at the center of the powder charge.

Any thoughts?

The thought that comes to my mind is:
"How does Nock's Patent Breech design, and more modern improved variations, square with this?
Their design improved ignition speed, and the vent is 100% at the bottom tail end of all the powder above it...

Joe S · « **Reply #9 on:** January 17, 2012, 06:48:44 PM »

I don’t know that answer to that Roundball. My comment was nothing more than pure speculation on my part. Are there reliable data that show velocity improvements for the patent breech? If the data that Daryl cited are correct and pressure is identical at all points regardless of the point of ignition, then a patent breech should have no effect on muzzle velocity.

BrownBear · « **Reply #10 on:** January 17, 2012, 06:56:48 PM »

My concern is cleaning. I have a rifle with the vent well forward, and a startling amount of fouling collects behind the vent over time. I bought the gun used and it functioned fine. But when I applied a breech scraper after my first shooting it felt realy weird down there.

I ground away with that scraper for what seemed like half an hour, continually getting black dust and occasionally large hard "crystals" of fouling. Each time I got a crystal, the face would feel rough again under the scraper until more turns polished it smooth. I'd almost quit, thinking I had it clean, and then I'd get another crystal or two and it would be rough again.

Subsequent measuring showed the vent is far forward of the face, probably putting it roughly in the middle of the charge. It works fine there in terms of ignition, but I'm religious about that fouling scraper now. "Plunging and pumping" the bore with a patch and jag does not clean the area behind the vent. If I'm getting a whopping 100 fps from the orward position, whooopee.

I can't tell, and I'd sure give it up for easier cleaning.

roundball · « **Reply #11 on:** January 17, 2012, 07:23:45 PM »

Quote from: Joe S on January 17, 2012, 06:48:44 PM

Are there reliable data that show velocity improvements for the patent breech?

Google searches will turn up a number of references for you...Nock patented it in 1787 for the express purpose of speeding up ignition and getting shot loads out of a barrel faster...pretty well proven / established function to this day, and improved upon somewhat to eliminate the fouling his design captured in it's horizontal ante-chamber.

Bob Roller · « **Reply #12 on:** January 17, 2012, 08:10:51 PM »

In the days of the Nock Patent breech,the powder varied in quality from wretched to superb with a good bit in between.The idea put forth by Nock's breech was to send a hot blast up thru the center of the main charge and create a detonation. There is supportive evidence for this according to the now deceased Lynton McKenzie. In the 1960's,Tom Dawson and myself ran experiments with the Nock system and found it to be of no real advantage with the powders available then which were DuPont,Curtis&Harvey and Austin and small amounts of King's which was an Ohio made powder. In the day of Nock,the idea did have some merit and keep in mind that a "Patent Mania" was going on in the UK at that time. One spoof was to show a gun that fired in every possible direction and killed every thing around it with the one shot it had.
I built a 58 caliber flint lock rifle a few years ago and made a Nock type breech plug for it and it worked fine. I knew there was no real advantage to it but having the material and the machinery,I did it any way. This plug had a 3/4x16 thread and the ante chamber was .358 with the flash hole at the very rear of it.

Bob Roller

roundball · « **Reply #13 on:** January 17, 2012, 10:39:56 PM »

So you're saying a design that made slower powder faster doesn't make faster powder even faster ??

Where are these test results officially published / documented ??

LynnC · « **Reply #14 on:** January 18, 2012, 05:13:36 AM »

This comes up about once a year it seems.

I have not found any touch hole location velocity data for rifles however testing was done long ago with a small mortar. See A Treatise of Artillery 1780 by John Muller. He tested a small mortar with 3 vent locations, rear, mid and front of same charge. The rear most vent location Always projected the ball the farthest, that is had the greatest muzzle velocity. It was followed by the mid vent and then the most forward vent giving the least distance/velocity.

Until someone tests a rear, middle, and front vent rifle barrel with a chronograph, we will not know the best location for a vent on a rifle barrel. But my bet is on the rear most vent

....................Lynn

Dphariss · « **Reply #15 on:** January 18, 2012, 05:33:05 AM »

Quote from: LynnC on January 18, 2012, 05:13:36 AM

This comes up about once a year it seems.

I have not found any touch hole location velocity data for rifles however testing was done long ago with a small mortar. See A Treatise of Artillery 1780 by John Muller. He tested a small mortar with 3 vent locations, rear, mid and front of same charge. The rear most vent location Always projected the ball the farthest, that is had the greatest muzzle velocity. It was followed by the mid vent and then the most forward vent giving the least distance/velocity.

Until someone tests a rear, middle, and front vent rifle barrel with a chronograph, we will not know the best location for a vent on a rifle barrel. But my bet is on the rear most vent ....................Lynn

Frontal igntion in smokeless was hoped to provide higher velocity. IIRC Elemer Kieth was part of a group that was trying to increase 50BMG velocity with frontal ignition. All they did was create pressure excursions and I think some blown up test guns. But this is from memory.
The Nock is supposed to give better velocity by igniting the powder faster via the pressure generated in the antechamber. According to Greener circa 1832 the Nock was only inferior to his

breech in distance a ball was thrown.

Dan

Bob Roller · « **Reply #16 on:** January 18, 2012, 06:32:57 AM »

The idea was to maximize what was available from any given powder of the day. If you had a really high quality powder,it would certainly be a benefit to get all that was possible from it.
There were numerous small powder mills when black powder was king and some were superb and others were inferior. During the American Civil War,the Confedereacy had imported high quality powder from England and maybe Canada and Union soldiers were known to rob dead and injured Southern troops of the powder they carried because a lot of the powders sold by contractors to the Union were of very poor quality.
We are fortunate today to have good to excellent powder and no real need for a chambered breech unless,like me,you just wanted to make the thing.

Bob Roller

Dave R · « **Reply #17 on:** January 18, 2012, 07:04:01 AM »

In theory placement to the rear is preferred however placing the touch hole liner too far toward the breechplug and having to notch the breechplug to allow the powder in the barrel to enter to the touchhole liner is best so the controlled explosion starts close to the face of the breechplug and travels toward the muzzle, However in actual field conditions the notch in the brechplug fills up with fowling and hinders ignition especially under high humidity conditions when fowling turns to wet mush! It also hinders ignition under low humidity conditions when the fowling turns hard like charcoal and blocks ignition to the main charge!In closing place the touchhole rearward so it's threads are just forward enough not to interfere with the breechplug!

Dave Reising

Dphariss · « **Reply #18 on:** January 18, 2012, 05:03:44 PM »

Quote from: Bob Roller on January 18, 2012, 06:32:57 AM

The idea was to maximize what was available from any given powder of the day. If you had a really high quality powder,it would certainly be a benefit to get all that was possible from it.
There were numerous small powder mills when black powder was king and some were superb and others were inferior. During the American Civil War,the Confedereacy had imported high quality powder from England and maybe Canada and Union soldiers were known to rob dead and injured Southern troops of the powder they carried because a lot of the powders sold by contractors to the Union were of very poor quality.
We are fortunate today to have good to excellent powder and no real need for a chambered breech unless,like me,you just wanted to make the thing.

Bob Roller

Yeah I wanted one too

The Nock breech requires good powder. Mine stops working in 2-3 shots if the powder produces large flakes in the bore. One will fall over the passage to the antechamber and prevent it from filling. Swiss never causes a problem, though I seldom shoot this rifle more that 10-20 shots without cleaning.
I sent a test breech to Larrly Pletcher to time.
The Nock was not the fastest but it was the most consistent. This is also my claim for the one I have. Very reliable and consistent.
This would have been important in wingshooting and shotguns appear to be the primary, if not sole, use for the breech in England. Greater variations in ignition from shot to shot would have produced more misses on flying targets.
I like mine but it requires the "breech in a bucket cleaning" to flush the antechamber but its no more trouble to clean than any other hooked breech.

Dan

Bob Roller · « **Reply #19 on:** January 18, 2012, 05:16:02 PM »

The first thing I do when I load a flint lock rifle or pistol is to push the vent pick into the touch hole and then when the load is seated,withdraw it,prime and close the frizzen.
After he shot,I do the same thing and never have a problem with a stopped up touch hole.
Does anyone have pictures they can post here of a late English half stock flintlock rifle. I have almost convinced myself to change direction on a half stock caplock I have started. The barrel is in the wood and no lock even started so it will be easy to remove the bolster breech and make up another Nock style. I have a 1x33x50 caliber GM barrel and think maybe another Twigg lock might be about right for it.

Bob Roller

Standing Bear · « **Reply #20 on:** January 18, 2012, 05:41:47 PM »

I went thru all of these posts pretty quickly so if I missed it...well a repeat.

The original post concerned Muzzle Velocity and several of the posts are talking about speed of ignition. To my mind two completely different measurements.

My sumary of these posts plus a little opinion is that location of ignition (touch hole at rear, middle or front) have would little practicle change on MUZZLE velocity in a shoulder fired rifle. Any increase in velocity would as easily be gained with faster powder, a larger charge or even a smaller vent hole.

Speed of ignition is another discussion all together and worthy of experimentation as applied to flintlock rifles and pistols. I may be hindering my speed of ignition by using Goex FFg as a main charge (prime w/ FFFFg). I use FFg as chronograph testing 30 odd years ago showed the FFg a little more consistant in MV than FFFg (done but not published by Tom Gillman). I have both patent breach plugs and flat. What tricks can be applied to speed ignition time?

Best to all,
TC

LynnC · « **Reply #21 on:** January 18, 2012, 08:09:09 PM »

Thanks for bringing us back on topic - Until someone chronos the vent locations all we have is speculation. I wish I had a chronograph and a spare barrel.

As a slightly off topic thought in response to other off topic posts

, I have two flint guns with the vent at the breech face. So long as you Don't wipe between shots I have never have any trouble with the vent clogging up, dry or humid. Clean up is easy with the pump flush method, the plug face stays nice and bright. Don't own a fouling plug face scraper thing.....Lynn

Dphariss · « **Reply #22 on:** January 18, 2012, 08:45:52 PM »

Quote from: Bob Roller on January 18, 2012, 05:16:02 PM

The first thing I do when I load a flint lock rifle or pistol is to push the vent pick into the touch hole and then when the load is seated,withdraw it,prime and close the frizzen.
After he shot,I do the same thing and never have a problem with a stopped up touch hole.
Does anyone have pictures they can post here of a late English half stock flintlock rifle. I have almost convinced myself to change direction on a half stock caplock I have started. The barrel is in the wood and no lock even started so it will be easy to remove the bolster breech and make up another Nock style. I have a 1x33x50 caliber GM barrel and think maybe another Twigg lock might be about right for it.

Bob Roller

The vent is not stopped its the passage inside the breech from the antechamber to the barrel that gets stopped up by a flake of fouling lying across it.
This ideosycracy leads me to think that the English had pretty good powder by the late 1780s when the design was patented.
Dan

Daryl · « **Reply #23 on:** January 18, 2012, 08:52:58 PM »

TC- your chronograph results are the same as mine. I mentioned this to DP here and he also achieved more consistant velcotiies with 2F over 3f.

Lynn - my findings exactly. No problems wet or dry - & no plug scraping needed with the flush (of any sort) method of cleaning. I can see merley running damp patches up and down would leave residue on the plug face, but I don't consider that cleaning, PC or not.

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.

Bob Roller · « **Reply #24 on:** January 18, 2012, 09:10:22 PM »

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

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Author Topic: Flash Hole Location and Muzzle Velocity (Read 13292 times)

Joe S

William Worth

Daryl

Joe S

roundball

Joe S

BrownBear

roundball

roundball

Daryl