FWB 124
The FWB 124 I am overhauling.

Part 1

This report covers:

  • Beautiful shape
  • Piston seal
  • More piston to clea
  • Breech seal and barrel
  • Now for the real dirty work!
  • Great technique
  • The new and old mainspring
  • New piston seal
  • Summary

Today we are going to clean the parts and internal places of the FWB 124 that I brought back from the 2022 Texas airgun show several weeks ago. And this will be a different type of report because in this stage I normally describe how I cleaned the parts and then lubricated them and assembled them. There would even be a short test at the end to see that everything went back together as it should. But not today.

Because this 124 was the dirtiest air rifle I have ever seen, I decided to slow down the report and show you more detail for the cleaning. It took me hours to clean it.

Beautiful shape

Just because the rifle was filthy inside doesn’t mean that anything was wrong. The parts all came clean and were in fine shape once the piston seal residue was removed.

Piston seal

Remember that piston seal? It took me 45 minutes of hard work to clean it

124 piston seal before
All the old piston seal that has dry-rotted into a hard waxy lump has to be scraped out and off. I scraped out a small depression in the old seal to show what has to be removed.

How do you clean a 124 piston? Well the piston head is has a deep depression in it that is formed to receive the base of the new seal, so all the old crud has to come out. I had recommendations to use solvent, and carburetor cleaner, but that’s messy and doesn’t get everything. Also, you have to be careful of the fumes from some carb cleaners.

I chose to dig out all the fragments of the seal with a flat-bladed screwdriver that you see in the picture above. That got about 80 percent of the seal but not all. I then used a dental pick to scrape out the rest. When I got close to the end I cleaned out the inside of the piston head depression. I used 0000 steel wool soaked in isopropyl alcohol.

124 piston seal after
After cleaning the piston head, which took 45 minutes, the piston was ready to accept a new seal.

More piston to clean

I didn’t just clean the piston head, though that took the longest time. I also cleaned the outside and inside of the piston body and the piston rod in the center of the piston. That makes the metal ready for lubricant, though not everything will be lubricated.

Breech seal and barrel

When the rifle came to me there was a pellet stuck in the breech. I expected to find other pellets stuck inside the bore further up. The record number of pellets I have removed from a barrel is 14, and with that one there were a couple steel BBs in the stack.  But with this rifle there was just a single pellet stuck in the breech. That’s good. It tells me the owner wasn’t a fool who kept loading pellets in hopes of shooting them out.

I rodded out the single pellet and found the bore was filthy as I expected. It was loaded with tiny particles of breech seal — what else? I expected the bore to be clean under that crud and it was. One patch was all it took to clean out all the stuff and then shiny metal.

The breech seal is in good condition but I removed it just to be sure. It is a little hard so I will replace it, even though it’s not absolutely necessary. However that lone pellet that popped out of the breech is NOT good. This rifle’s owner needs a fresh case of, “Learning about premium pellets” because sinker larvae and trick pellets, of which this is one, are not for a 124, any more than we would shoot darts in a 10-meter rifle or put kerosene into our car’s gas tank.

124 breech
The breech seal looks okay but that pellet sure isn’t! BB’s gotta tell the rifle’s owner what pellets to shoot.

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Now for the real dirty work!

By this time I had wiped off the breech seal particles from all the other rifle parts and they were everywhere. That, plus the condition of what I found inside the compression chamber tells me that SOMEBODY shot this rifle repeatedly, trying to get it to work! That is the very definition of crazy.

What awaited me inside the spring tube was a mass of breech seal material that was smashed into the end of the compression chamber — the deepest spot in the spring tube and the one that’s hardest to reach! Oh joy!

Once again I did not use solvent or carburetor cleaner for the same reasons I told you before. I used a long-bladed screwdriver to reach down to the end of the compression chamber and lever out the chunks of rotted seal material. Imagine brain surgery with the surgeon wearing boxing gloves.

124 spring tube with driver
Time to dive in deep and start scraping.

This is why I tell you that if you want to work on spring-piston airguns you need to own long-bladed screwdrivers. Whenever I go into a pawn shop they are one of the things I always looks for.

After scraping out the compression chamber for about 45 minutes, I could see that only 10 percent of the seal material remained. It looked like it was going to be super stubborn to remove, so I borrowed a genuine dental pick from my neighbor, Denny, and taped it to the end of the long screwdriver. I used Gorilla tape because, with apologies to Red Green, duct tape just wouldn’t cut it. This is the first time I have ever done this, but it does work.

124 pick on driver
I taped the real dental pick on the end of the long-bladed screw driver with Gorilla tape.

I scraped for about ten minutes and did get about half of the remaining seal material out, but the pick just wasn’t going to get it all. So I taped a piece of 0000 steel wool on the end of a long half-inch wooden dowel and saturated it with isopropyl alcohol. Then I chucked the dowel in my electric drill and pushed it into the spring tube. After about a minute of turning that steel wool against the end of the compression chamber it was squeaky clean. This is another technique I have never tried before, and this, plus the dental pick trick, is the reason this entire report is about cleaning the 124 and nothing more. This is good stuff that I want to remember, no matter who else does!

124 wool before
I taped the 0000 steel wool to the end of a half-inch dowel with Gorilla tape. Then I saturated the wool with isopropyl alcohol.

124 wool after
This is what the steel wool looked like after a minute of spinning inside the compression chamber of the FWB 124.

Great technique

I was surprised the steel wool held together and that it stayed taped to the dowel. I was also surprised that my cordless electric drill could chuck up a half-inch dowel and not loose it while spinning. This is a great technique for cleaning compression chambers in spring tubes! I just never had one this dirty that needed cleaning.

The new and old mainspring

At this point in the process I would clean the mainspring if I planned to use it again. But I made the decision not to. The new spring will replace it and there is nothing for BB to clean.

124 springs
The old spring is on top. You can see that it is a little wobbly, compared to the new spring below. What you can’t see are the shiny spots worn on the coils in several places. Those are high friction points where vibration creeps in. You also can’t see that the old spring was improperly lubricated. It was very dry in spots.

New piston seal

I had a new piston seal on hand from the UK, but it was made of hard material and it also needed a lot of sizing to fit inside the spring tube. I opted to go with a new 124 piston seal from Pyramyd Air. I knew it was made from more pliable material and I was delighted to find that it will need very little sizing.

More pliable material means that a looser fit in the compression chamber will still work because this is a parachute seal whose end will expand to seal the air. What that means is hopefully higher velocity.

124 piston seal
The piston seal from Pyramyd Air is pliable and also sized to need very little fitting to the 124 spring tube. Note the bottom of the new seal. That shows you all the stuff I had to dig out of the piston head.


There was a lot in today’s report. It’s a reminder for myself and notes to follow for others who want to overhaul an FWB 121/124/125/127.