I picked up a nice HW55 last fall and had a lot of fun shooting it all winter indoors. But occasionally I could hear what sounded like metal on metal during cocking which concerned me. The last thing I wanted to do was ruin a fine, classic 10 meter gun. I finally got around to taking it apart to see what could be done to get it smoothed out. Once apart, I was relieved to see that the internals were in good shape, the only obvious problems being a worn spring and a leather seal that was dry and encrusted with black residue of some kind.
I was able to rescue the leather seal by soaking it in oil and scraping off the dried-on residue, but in the end decided to replace it with a Vortek adapter and seal. The spring also got replaced with a Vortek 770113-26. To provide better seating for the new spring, I also made a short top hat and a thin washer to slip over the guide. These reduced the available spring space by about 0.200". Other than cleaning everything up, the only work on the internals was some light sanding of the back end of the piston, and some light smoothing of the cocking slot with a diamond file.
Lubrication was done using a blend of moly with the grease that came with the spring. I initially tried applying a minimal amount of lubricant to the internals, but the sound of the dry and rather tight fitting seal over the honed bore didn't sit right with me, so I opened it up again and burnished some straight moly grease into the honed area of the bore. This eliminated the sound of seal drag, but also caused a little bit of that burned lubricant smell so familiar to springer shooters. This may go away with time, I don't know.
The final result was a very smooth cocking and firing cycle, and an increase in power over the original, but worn, configuration. Average velocity with JSB Middle Weight pellets came in at 652 fps, with an ES of 13.3 over 20 shots. For comparison, my FWB 300s is generating 618 fps with an ES of 8.1 with the same pellets. Overall not a bad result for a 45 year old rifle!
I was able to rescue the leather seal by soaking it in oil and scraping off the dried-on residue, but in the end decided to replace it with a Vortek adapter and seal. The spring also got replaced with a Vortek 770113-26. To provide better seating for the new spring, I also made a short top hat and a thin washer to slip over the guide. These reduced the available spring space by about 0.200". Other than cleaning everything up, the only work on the internals was some light sanding of the back end of the piston, and some light smoothing of the cocking slot with a diamond file.
Lubrication was done using a blend of moly with the grease that came with the spring. I initially tried applying a minimal amount of lubricant to the internals, but the sound of the dry and rather tight fitting seal over the honed bore didn't sit right with me, so I opened it up again and burnished some straight moly grease into the honed area of the bore. This eliminated the sound of seal drag, but also caused a little bit of that burned lubricant smell so familiar to springer shooters. This may go away with time, I don't know.
The final result was a very smooth cocking and firing cycle, and an increase in power over the original, but worn, configuration. Average velocity with JSB Middle Weight pellets came in at 652 fps, with an ES of 13.3 over 20 shots. For comparison, my FWB 300s is generating 618 fps with an ES of 8.1 with the same pellets. Overall not a bad result for a 45 year old rifle!
