Breech plug design
 

About a month ago tpcollins showed me this diagram of a breech plug. I saw that it was posted in early 2008, and assumed the author of the diagram had probably made some revisions, in what he wrote, was the ideal breech plug for use with BH209.






At first glance, i could see that i didn't much agree with the assessment of this being an ideal breech plug. In my mind the flash hole is much too large, and the depth of the recessed face is much too deep. Many breech plugs are only about 1 1/4" long. A recessed face of 0.6" would be half way into the plug, and put the powder a right up next to the primer. Coupled with the large flash hole, this should result in quite a large pressure on the primer, and substantial blow back.

Well, i didn't put too much worry to this diagram, because it was published so long ago. I was thankful that i had never seen this diagram when i was learning what it takes to make a breech plug reliably ignite BH. Had i seen this diagram 2 years ago, my education in breech plug design could have been stunted. The breech plugs i use, are not like the diagram, but they are 100% reliable igniting BH209. I had thought the breech plug design shown in the diagram to be past history, and didn't think about it anymore.

However, just last week an individual that has in the near past, pushed this diagram as being the cat's meow, claimed to have a new great set-up for shooting BH. I fear that shooters could get misled by this individual. So now seems a good time for me to share specifications, and pictures of breech plugs, that really work good.









The plug on the left fits the TC Omega. The plug on the right fits CVA rifles. They are very similar, and they both ignite BH reliably. The TC plug has a 0.029" flash hole. The CVA plug has a 0.029" flash hole that started out at 0.028", but is now 0.001" larger from being used for more than a few shots. The TC plug has a 1/8" flame channel. The CVA plug has a 5/32" flame channel. They both ignite BH reliably.









The recess in the end of the TC plug is 0.37" deep; the recess in the end of the CVA plug is about 0.31" deep. The recess in the TC plug is about 0.37" diameter; the recess in the CVA plug is 0.31" diameter. Both these plugs ignite BH209 every time a primer is popped without delay, in sub-zero, or summer weather.

The TC plug comes with the Omega, when the rifle is purchased; the CVA plug is aftermarket.

When fired, breech plugs with short flame channel, exert more pressure on the primer than plugs with a longer flame channel. This i have learned the hard way. Primers, scopes, and breeches, with soot all over them were my first clue. Myself, i have never used a breech plug, or a vent liner with a flash hole larger than 0.033".

The diagrammed plug would probably ignite BH just fine, but the short flame channel, and large flash hole will exert excessive pressure on the primer. The large flash hole will only get larger when the plug is put to use. The flash hole in all breech plugs grows with each shot.

hi all
thanks for details
the same thing i made .but the black powder is not entering in to breech plug(flash channel) and it is not burning the black powder also.
my doubt is in actual condition the black powder will enter in to the breech plug(up to primer pocket) or not?

ROVER

And then I would add to..

The length of the flash hole from the powder is not near as critical IF the breech plug has the ability to 'BREATH' for the lack of a better word.

The plug on the right will ignite BH just as reliable as the one on the left. In addition the plug on the right will go longer before the cleaning of the 'flash channel' is necessary because it can contain more volume.



I am not an artist or a mechanical wizard but here is the basic drawing that I tend use.





This is the modification of a Triumph breech plug. The Triumph plug is really long and a factory plug will ignite BH without a problem unitl the 1/8" flash channel becomes clogged.

I modified mine by opening the flash channel with a #21 bit and installing the vent liner in the nose of the plug. Ignition was great even with the coolest primers.

The flash hole will prevent the powder from entering into the flash channel. This allows the flash channel to act as a 'expansion chamber'. This reduces the pressure on the primer. It is not desirable to have the powder leak into the flash channel

If the powder is in direct contact with the primer, the pressure on the primer is excessive. This pressure pushes soot right through the primer, in muzzle loaders.

If you are experiencing powder ignition problems, be sure you are using primers hot enough to ignite the powder you are using.