Breech Plug design: seal up blow back & shoot Blackhorn209

If an internet search brought you here looking for a solution to your woes with a Remington 700 ML or Ruger 77/50 muzzle loader: Don't worry, you are in the right spot and we have the fix you are looking for.    Just keep scrolling down or click here for our wonderful 209 sealed breech fixes for those rifles.     We are a dynamic business and constantly adding to this blog.

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In this installment, I figured it was time to discuss breech plugs: what works, why it is probably different than most think, and why I think it works.   I'll also showcase our service of retrofitting vent liners into breech plugs (to help them work more reliably, accurately, and better with Blackhorn209 powder).   Yes: we can help with more muzzle loaders than the Ruger 77/50 and Remington 700 ML.

One of the first things most folks realize when they examine our kits, is that the Badger Ridge breech plug, is unique and different from the rifle's original.   Our kits won't work with the original breech plug!  Our system just plain works.  Because our design works, folks frustrated with igniting BH209 in other rifles send us their breech plug for modification.

BOTTOM LINE UP FRONT:  A good breech plug is a compromise of many different features.  Our design works with any muzzle loader safe powder (we can make other rifles' breech plugs work with any  muzzle loader safe powder... like Blackhorn209).

I'll try not to delve too deeply into chemistry, physics, and thermodynamics both because most won't care about the details, but also I'd probably rapidly reveal the limits of my understanding.  But some basic understanding is required.  First, heat flows from hot to cold.   There is truly no such thing as cold...  cold is a relative lack of heat.   Heat can be thought of as a form of energy...  thus a hot piece of metal just has more energy than a cold piece of the same metal.  So heat from discharging a primer will flow into the metal around it, and into the powder charge we want to start burning.

Badger Ridge breech plug with vent liner

So you might be thinking "What does that have to do with muzzle loading and breech plugs?"

Well every time we discharge a primer we convert the chemical energy of the primer into heat and expanding gasses.   Seeing our real goal is to get the powder burning, the primer's flash needs to be directed into the powder charge, and it has to stay hot to get the powder charge burning.   It is the powder charge that turns into more heat and more expanding gasses that push the projectile down the barrel.

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Generic breech plug from BH209.com

So at first it seems to get reliable ignition, you just need to get the primer close to the powder, and minimize the metal in between.   And many of the first generation of inline muzzle loaders followed that design idea.  But if you have seen any of the more modern breech plugs, especially those that use 209 primers, and are reliable with Blackhorn209: there is a large expansion chamber in front of the primer, creating a big air gap, and has a small hole at the end that abuts the powder charge.  

Just thinking about heat flow, all the metal that makes up the wall of that expansion chamber, and that super cold winter hunt you might take your muzzle loader on, it seems stupid to lose some primer heat to it.  So why does a good breech plug have that chamber?   And why would it have a metal constriction on the end of it (ie a vent liner or small flash hole)?

Before I answer that, let's consider another reason the flash chamber doesn't make sense at first glance...  as the primer's burning gasses expand they would cool just through the act of expanding into the flash channel.

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Fact: pressure, volume, and energy are all connected.     For a steady state, ideal reaction I learned in High-School Chemistry:

PV = nRT 
 (or Pressure * Volume = number of molecules * their constant value * Temperature)

Or in simpler terms if you don't change the temperature but you increase the volume the pressure will decrease to keep it all in balance.   But in real life you get both: as the hot gas expands into the chamber it loses heat just from the expansion, even before we take into account the heat that flows into the cold walls of the breech plug!

"OMG" you exclaim, "I knew that primer should be right up against that powder to be 100% reliable!"   But, I'd say practice has proven that to be wrong, our breech plugs have expansion chambers for good reason:  to keep the powder charge from blowing up the primer and venting gas all over the shooter and dropping accuracy!

Remember, after we get that powder ignited and burning, it produces a whole lot more pressure and heat than that tiny, thin walled primer could ever contain.   We want all that heat and energy to push that projectile down the barrel, but because there is that small flash hole right next to it, the gas shoots backwards into the expansion chamber that is being sealed by the primer.    The trick here is that the flash hole is so small it greatly restricts the rearward flow, and what flow makes it through, finds itself rapidly expanding, dropping pressure, and cooling as it flows into the primer's flash chamber.  And that is why the flash hole and flash channel (chamber) are there.   They work together to keep the pressure from burning powder from blowing up the sealed primer.

Keeping that primer sealed and intact keeps the mess in the breech plug, and tends to increase accuracy as the pressure seen at the back of the projectile is consistent shot to shot.

Badger Ridge's Hunter Breech plug versus OEM

Our sealed breech systems have the expansion chamber with a 209 primer sealing one end of it, and a removable vent liner so that we avoid the bad things that happened without an expansion chamber (and I say happened because many of the first 209 designs lacked the expansion chamber and vent liner design, but beware: they are still out there!)

Lets over simplify and say that there are four basic ideas on how to make a breech plug.  Two are bad ideas, and two work well with the back pressure burning powder generates:

1. Don't even try to seal the primer and vent the back pressure (ie Blow-Back) into the action; let it leak out.   This makes a horrible mess, and tends to shorten the life of the system as sticky corrosive goo covers everything.   This also tends to send flying fragment primers and percussion caps into things, like the shooter.  Also these systems won't work with Blackhorn209 as it has to be sealed up.  (BAD IDEA)

2. Seal up the 209 without an expansion chamber and vent liner: Direct all the heat into the powder charge but blow up the primer/cap due to blow back, and then have blow back escape where ever it goes.
  This tends to drop accuracy as you don't control the time nor pressure when the rupture occurs.  Plus just like #1 above, it makes a mess and sends pieces of primer all over the place.  And just like #1 above, Blackhorn209 does't like this will yield unreliable performance at best.  Again: Flying primer fragments are dangerous!  (BAD IDEA)

3.   Seal the 209 up with an expansion chamber that has a small orifice at the end to deal with the back pressure the powder charge generates.

4. Use large primer holders/brass cartridge cases that are strong enough to hold the pressure in.
   209 primers in and of themselves are not strong enough for #4.  Most systems that use #4 use primer carriers and magnum rifle primers,  also break actions enclose the 209 primer in steel.

-The original #11 percussion cap systems on the Remington 700 and Ruger 77/50 followed 2 mostly.
-The Remington 209 modification followed #1 (note the big slits on the side).
-The Canadian 209 mods for both rifles did a bit of #1 and #2 in my book (sealed until back pressure unseated the primer, also tended to blow up primers).
-The Remington Ultimate Muzzle loader uses #4, but is very expensive and requires reloading gear to re-prime the cases.  
-Our 209 kits use #3.  And we can modify other rifle's breech plugs to do the same.  The down side is that the chamber must be sized right: it is "Goldilocks" work.   Not too big (lose too much primer heat) not too small (blows up primers).  The other down side is that the orifice/flash hole slowly erodes with each shot.

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A knight BP that had its vent liner soldered in (removed and ready for a new vent liner)

Remember that back and forth flow of hot burning gasses (primer residue and combustion gasses) erodes the flash hole with each shot.   

​When breech plugs that don't have vent liners open up, they loose accuracy.   Most folks don't realize this, and just know that  their rifle doesn't shoot like it used to.  They typically look for loose scope mounts, bad scopes,  loose action screws, etc.  I get calls from them and they are frustrated as they can't seem to figure out why the rifle isn't shooting well now.  For some, the light bulb comes on when I start asking about the size of their breech plug's flash hole.  And do they have a gage pin to measure it?

I'm confident, that manufacturers know that flash holes have a limited life.   Some just go with a cheaper breech plug, or even solder in vent liners!    Seems they just want to sell entire new breech plugs.   But we usually can offer a different solution: modifying the breech plug to take a vent liner.   Most of the time we can convert those breech plugs to take inexpensive vent liners and also put an expansion chamber between them and the 209 primer to keep the primer from seeing excessive pressure. ​

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The vent liner is the removable flash hole our breech plugs use

So there you have it,  a good 209 breech plug is a compromise between directing the energy of the primer into the powder, and keeping the pressure from the burning powder from blowing up the primer.  To use Blackhorn209 powder, it must be sealed up.  To use 209 primers the breech plug needs an expansion chamber that is sized to allow expansion but not rob too much heat, and it needs a small orifice in the end that abuts the powder charge.   

At Badger Ridge, we go a step further by using inexpensive replaceable vent liners.  Our  breech plugs are designed for longevity: we use vent liners to cheaply replace the flash hole instead of forcing shooters to buy new breech plugs.  And we sell pin gauges so that you know when to replace the vent liner:  if it goes through its time to replace.

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