Just in case you were wondering:
FAC Export Spring Dimensions for The Winchester 435 .177 air rifle born in 1969 are:
Wire Dia: 0.120"
Outside Dia of spring: 0.813"
Inside Dia of spring: 0.570"
# of Coils: 39
I needed to order a new seal for my soon to be sold Winchester 435.
Figured I would order the UK spring as well. BB Pelletier says the power difference between UK spring and US spring is negligible due to short stroke design of the gun. Figured having both springs on hand would be better than two of the same. UK springs are easier to install since the pre-load is less.
The UK spring is 10" OAL. Didn't measure the other specs as I wanted to get it installed ASAP. It is the "Standard Spring" from the Chamber's Airgun Spares website.
The rear guide is slightly looser in the new UK spring versus the old US spring. Only slightly. Rather than invest any more money in the gun with a new guide from JM, I simply changed the spring and seal.
Soaking the seal in neatsfoot oil over night seemed like a good bet. In the intervening time I cleaned out the old dried lube, tarred the new spring, chased some threads, took off some edges, and marveled at the simplicity of this gun.
The seal is a multipiece, leather job. I had to buy all 4 pieces instead of just the cup (which was dried out and too flaky to re-oil). Probably a good thing since the original leather washer and leather (?) plug parts are as hard as Delrin.
After putting moly on the piston and three-ball piston-stem-holding plates I re-assembled the whole thing in about 10 minutes. Has to be the easiest gun I have opened. To keep the ball bearings in place, I put a dab of moly in each channel. I then put the ball bearings in and add another dab. Then I put that inner sleeve in the freezer. I use Honda Moly 60 and it seems to get pretty drippy in this heat. Freezing the part with the moly and balls in place gives me a few more minutes of leeway when working with parts that want to drop out and ruin your day.
The sighting system is pretty good,
but clearly I was having trouble picking the same POA.
FTS is always my pellet of choice in any caliber (except .20), but the 5 shot group for the RWS Super Points is pretty impressive. Most of the 5-shot groups look like 4-shots. The Super Points group looks like three shots. I have seen this same preference for Super Points in a few Daisy Avanti 853s. Must be some velocity threshold for them.