If you need a PENTRATING FLUID to remove a breech plug - this is the best!

[Flint62Smoothie]

FWIW the best penetrating solution one can use is a DIY homemade mix of 50% acetone and 50% automatic transmission fluid (ATF).

Years ago “Machinist Workshop Magazine” did a test on penetrating oils. Using nuts and bolts that they 'scientifically rusted’ to a uniform degree by soaking in salt water, they then tested the break-out torque required to loosen the nuts. They treated the nuts with a variety of penetrants and measured the torque required to loosen them.

This is what they came up with:

• Nothing: 516 lbs
• WD-40: 238 lbs
• PB Blaster: 214 lbs
• Liquid Wrench: 127 lbs
• Kano Kroil: 106 lbs
• (ATF)/Acetone mix (50/50 mix): Only 50 lbs!

[Bugyotsuji]

Hey, those are some interesting figures! Wow. Did they say how long they soaked it, giving the stuff time to go to work?

 

One thing to be aware of Dale is that towards the end of Edo there is evidence to show that some late-manufacture bisen breech screws were pinned in place, i.e. for the sake of a better seal, designed never to be opened. (The crosspiece can be mega hard to spot.)

[rickystl]

Thanks Dale

 

That is very useful to know.

 

Thanks, Piers.  First time I've heard that.  Interesting.

 

My Tan is in shooting condition.  I removed the breech plug for inspection.  It was little more than finger tight.  European style barrels typically have a shorter plug with fine threads.  It seems the Japanese barrel plugs with course threads made up the difference by simply making the plug longer.

 

When I reinstalled the plug on mine, I coated the threads with high temperature automotive thread sealant.  The sealant never really hardens completely.  Same as they use on spark plugs.  That way, if the breech plug ever needs to be removed again, it's easy.  The sealant also keeps both the male and female threads from forming a rust bond over time.

 

Rick

 

[Bugyotsuji]

Rick that sounds like a great idea. I have removed bisen screws in the past with some kind of black sealant around them, as if someone had had a similar thought.

 

To extrapolate a little, it may have been the fact that the guns on Western ships approaching Japan's shores had so much greater range. Japanese cannons needed to be sealed more efficiently, so the barrels were filled with seawater to rust-seal the breech plugs. As a spin-off from this, or in conjunction with this, infantry guns began to be made with even finer tolerances to gain extra bang and range, (vent channels became so small that only a fine cleaning wire could work through) and troops were encouraged never to remove the bisen screw when cleaning their guns, i.e. to deliberately allow a build-up of grunge around the screw. Personally I wind a section of kitchen paper towel two or three turns around mine after every clean to make for a tight fit to the right position.

 

PS What you say about European gun threads is interesting for me as I have a pistol with an uncharacteristically short bisen screw. The screw is stuck so tight that I have given up on opening it, but I was wondering if such a short screw could even be practical, to the point where I thought the gun could be a fake. It was only when I finally managed to clean out the vent hole, (yessss, fantastic, it does have a viable fire channel!) that I became convinced that this gun was/is the real McCoy.

You have opened the possibility in my mind that the gunsmith used a Western technique in the manufacture of this matchlock pistol.

[Alex A]

Handy to see, for various jobs, thanks.