Shape of Breachplug Vs Accurcy

[Frizzen]

Do any of you know if the shape of the face of the breach plug has any effect on accuracy or not.
I'm  comparing a flat face vs a conned face. This will be on a pistol with the nipple located in the
back center of the plug.

[Daryl]

A coned breech, ie: with the bottom of the cone terminating at the nipple flash channel, should increase pressure at the nipple and thus burn them out sooner. This cone should also introduce burning at the very posterior of the charge - that sounds good - but?  Does it really make a difference? Is the difference mreasureable and has someone experimented with a variety of percussion breech shapes? Sorry-0 I've the same questions, but am satisfied with the situation of normal breeching and angled flash channels.

[okieboy]

 I think this is a very interesting question. I don't know the answer, but what looks obvious to me is that the flat face should be easier to get clean. Being easier to clean has accuracy implications both short term (as in a match) and long term (maintaining your gun).
 When building conventional side flash channel guns, one is often advised to line up the flash channel with the face of the breech (wheather a flintlock vent or a percussion drum) and then "notch" the face of the breech. There is no shortage of old guns done this way, but where is the experimental proof that it is better than moving the flash channel forward to facilitate cleaning?
 Maybe this is something for Mr. Pletcher.
Okieboy

[roundball]

Do any of you know if the shape of the face of the breach plug has any effect on accuracy or not.

Just to toss out a wildcard thought...it's also interesting to remember patent and chambered breeches...don't recall ever hearing of any accuracy issues with them due to their designs

[Daryl]

I believe the coned breech is the easiest to clean - we flush them in water. There is NEVER any scraping of plugs involved as the rush of water cleans everything out. It's the corners in the square version of plug that would possibly 'hang' fouling. As to accuracy- it may take a machine rest to discover any accuracy variation.   

[northmn]

Round bottom rifling vs square bottom?, breech plug shape, flint vs percussion?  Take a lot of different rifles to determine any differences. About the time you compare one to another someone will come up with another one that will  perform differently.  Take two barrels by the same maker and same configuration and you may find they like different loads?  To determine any differences statistically the testor would have to compare about 15 rifles with a rounded breech made the same to 15 with a square breech.  Then you get into load development differences and issues.   Larry timed a mule ear against a regualr lock and found no difference, but some shooters will swear that a mule ear with its direct ignition will be "faster"  Some may some may not but notice they never really took the world by storm.

DP

[Larry Pletcher]

We timed flat vs coned breeches but did nothing that related to accuracy.  The results are in an ALR post sometime back.  I'd have to look it up.  I believe the flat breech was a little faster, but I hate to rely on my memory this late at night.

The mule ear vs side hammer test had some areas that need more experimenting.  I believe the hammer-throw on the mule ear was so short that it had little time to accelerate.  Needs more thinking.
Regards,
Pletch

[Dphariss]

If you CHANGE a flint gun to a cupped breech from a flat it may be necessary to do load development.
In percussion guns the flash channel in the breech will determine, to some extent, the pressure to the nipple base. Most come into the cone off center if angle drilled
All the old percussion patent breeches  were coned to some extent to reduce the length of the channel.
And most of this technology, flint or percussion, was developed by the British who were trying for increased velocity or better shot patterns.

Dan

[northmn]

Larry, I think you may have problems in comparison.  The big issue on mule ears over regular locks was always that they were faster because the nipple was directly drilled into the barrel.  No flash channel.  Same for underhammers.  Unless you could compare several side slappers agains several typical locks you could run into problems.  I was satisfied that their was no major difference between just the two you tested which would have to occur to impress me with the possibility that an experiment would be worthwhile.  Many percussion locks, and I have one, have a very short throw off of a stirrup system.  Mine needs to be brought to full cock to put a cap on it.  The half cock practically covers the cap.  Typical of the "Hawken" locks. 

DP 

[Larry Pletcher]

Larry, I think you may have problems in comparison.  The big issue on mule ears over regular locks was always that they were faster because the nipple was directly drilled into the barrel.  No flash channel.  Same for underhammers.  Unless you could compare several side slappers agains several typical locks you could run into problems.  I was satisfied that their was no major difference between just the two you tested which would have to occur to impress me with the possibility that an experiment would be worthwhile.  Many percussion locks, and I have one, have a very short throw off of a stirrup system.  Mine needs to be brought to full cock to put a cap on it.  The half cock practically covers the cap.  Typical of the "Hawken" locks. 

DP 

I agree with all you said.  The chance came to us to work with a mule ear whose plate fit a small Siler lock mortice - so we jumped at the chance.  The small Siler we used was typical, but the mule ear was a "one off" hand made one.  Our experiment ended since there were no more mule ears to compare.  I believe I was careful to qualify our results by mentioning that we compared one each.  We could keep all other variables in check -- same barrel, caps, powder, humidity, timing equipment, etc.  My concern with the mule ear was that the hammer throw was so short I wasn't sure the hammer developed any inertia.  With worlds of time, I would have enjoyed working with a variable throw length to see if it was faster or slower with a longer throw.  Conventional wisdom would say the shortest throw is quickest, but - can a hammer throw be too short??  I don't know.

So many experiments and so little time,
Pletch

[Daryl]

Given enough inertia to fire the cap hard, stands to reason the shortest 'throw' wold be the fastest - given the springs for strong ignition - just as the shortest firing pin travel results in the fastest 'lock time' for a modern bolt gun - bolt or hammer or spring driven such as the Martini Cadet - the fastest of normal actions. An underhammer such as those with huge soft trigger-gaurd springs, having a lot of travel will likely have slower lock time than those with drums or patent breeches and stiff springs and shorter travel. A thought.

[Frizzen]

I've been thinking about this some, and Yazel who has been making flat faced breach plugs in
his pistols for close to 50 yrs, and they hold records that I'm sure that there is no difference in
accuracy or none that you can detect in conned vs flat. I believe it's just which ever would be
the easiest to clean and you would perfer. Me, I have both and both shoot accurate.  Thank you
all for responding.
                                Phil