Walther LG-55

Walther LG-55T DST. 

The Walther LG55 was a fully-fledged match rifle and was made in large numbers from the mid-1950s until it was replaced by the LGV in the 1960s.

This particular example has double set (hair) triggers and a Tyrolean stock.

Walther LG-55 Manual.

Walther LG-55 (ambidextrous stock) 

With thanks to Marty.

Walther LG-55 piston seal repair 

With thanks to Len (and Gaines for the sketch).

Len wrote on the American Vintage Airguns forum:

Anyone who has ever undertaken the task of resealing any of the vintage Walther LG5x series of rifles is no doubt familiar with this sight.
This particular gun is an LG55, and sadly, even though the gun was no longer able to expel a pellet from the barrel, someone tried repeatedly to cock and fire the gun, for reasons unknown to anyone familiar with spring air guns.

Once the remainder of the disintegrating seal was removed, the damage from continuing to fire the gun becomes apparent. The piston seal retaining nut has been split into two pieces as a result of being mercilessly hammered over the threaded stud on the piston latch rod. The threads on the stud are destroyed. If you look at the washer, just to the left of the split retaining nut, note that at the 6 o'clock position that the washer has actually been deformed as a result of being forced into the transfer port at the end of the chamber. Had it not been for the exceptional build quality of these vintage Walthers, the gun would have sustained far greater damage as a result of the abuse.

A close up of the threads - completely destroyed.

I now had to decide on the best course of action in order to repair the gun, without going to the expense of trying to obtain a new piston. A quick check of the thread size shows the OEM thread to be a 6.5 mm x .75 mm thread. The stud was tested and found to be quite tough, but workable, so I then chucked up the piston in my lathe, and turned the stud down to just under 6mm. A 6mm x 1mm thread was then die cut onto the stud. Looking good so far.

Next, a new retaining nut was machined, using the remains of the old nut as a pattern. The nut was tapped 6mm x 1mm to mate up with the modified stud on the piston. A screwdriver slot was milled into the top of the nut, just as in the original, to allow for adjusting the seal fit to the bore.

A replacement reproduction piston seal was ordered from JKI (John Knibbs International). These seals are of exceptional quality and are the closest to the OEM part that I have seen to date. The washer that fits between the retaining nut and the piston seal was then straightened out and cleaned up. The piston seal is then placed on the piston, the washer, and then the retaining nut, with just a small drop of service removable, threadlocking compound. The piston assembly is then test fit into the chamber and the retaining nut adjusted to achieve the correct fit of the seal to the chamber walls. The assembly is then set aside to allow the threadlock compound to cure.

Gaines added:

Len elaborated:

I've enlarged the first pic of my original post to further clarify what is very likely causing the deformation of that backup washer. If you look at the orientation of the deformed section of the washer indicated by the two red arrows, you will note that it is 180* from the cocking arm slot in the piston - which is the exact location of the transfer port. Now look at the way that the washer is tilted - the top section is pushed further in than the bottom, due to the bottom portion of the seal crumbling, while the top section (near the transfer port) remained relatively intact.

Len described the OEM Walther spring:

Here is a pic of the paint marking on the OEM mainspring. This one is quite well preserved, while in some cases, it is barely legible.