Canadian Airgun Forum

My P17 valve was leaking and needed some attention so I tore it down this afternoon and replaced the stem seal. All works fine now.

When swapping out the seal I did notice another difference between the Chinese P17 and the German HW40. Many seals are different sizes.

PISTON SEAL - The Chinese piston seal seems to be a tiny bit larger than the 116 that we use to replace it. The 116 works great but when comparing the two seals the original Chinese seal is slightly larger in diameter and slightly thinner is cross-section. The 116 stretches a bit more during installation and this likely effects the fit so it works.

STEM SEAL - The P17 seal on the end of the stem seems identical to a standard 006 seal so the replacement was easy. Ironically, there is a Metric seal that is very close to the 006.

VALVE PLUG SEAL - The seal on the brass stem plug was not a Standard 009. The 009 was slightly larger and I couldn't get the plug screwed in with the larger seal. The factory "stem plug" seal is definitely smaller so I re-installed this seal. I'm guessing that a 008 might work here but a Metric seal is likely the answer (M1.78x4.76mm). Possibly more force could have been used to coax the brass threads with the 009 seal into the aluminum piece but I didn't want to take the chance.

BREECH SEAL - The seal on the P17 breech is not the same size as the HW40 breech seal. They are very close but not the same. The P17 breech seal is slightly smaller. Thankfully the 009 works fine and actually gives me another 4 fps average velocity. The Chinese breech seal and valve plug seal seem to be the same size (both slightly smaller than 009). There is a Metric seal that measures M1.78x4.76mmID as compared to the Standard 009 that measures 1.78x5.28mmID (.208"IDx.070"CS). Here is a pic. The center oring is from the P17 breech. The left and right seals are 009 from two different retailers.



None of this matters much as long as what we have works. The only point I am trying to make is that it appears as though the P17 uses Metric orings and the HW40/P3 uses Standard orings.

Cheers,
Todd

You need to take into account changes in production (at both ends- the HW's and the Chinese-made)- often sizes will change over time (this is especially true of Chinese products it seems). My point being that this sizing difference may be true when comparing HW40 'A' vs. P17 'A', but may differ when comparing HW40 'A' with P17 'B'.

Why would the Germans have used 'standard' or imperial measurements? Seems a bit strange!

_________________
Please note: I do not conduct business through Private Messages (PM's) in online forums. Please do not send a 'PM" with a business-related question.

I resealed my P17 not that long ago with the closest available imperial o-rings.

_________________
Daisy Red Ryder

Hi Derek... many thanks for the reply... you confirmed that 008 will work in the breech and the plug. Now I don't have to track down Metric seals

Hi Eric... I don't know why Weihrauch uses the Standard oring sizes. I was a bit surprised when I first heard. I think the first 009 breech seals I purchased were back around 7 or 8 years ago. In order to change sizes wouldn't they have to change the machining on the parts? The grooves are designed for these sizes. My 11 year old HW40 and my 8 year old HW45 both have 009 breech seals. Apparently, this is still the HW breech seal size today. Tim McMurray (Mac-1) gave me the sizes. He stated 009 for the breech seal and 117 for the piston. These fit fine on my 1999 HW40 (introduction year). The sizes didn't seem to change on the HW40.

Back in 1984/85, when the HW45 was first introduced, it has a smaller Metric breech seal. I think the size was 1.5mmx5mm. By 1986 the seals were 009 Standard size. As far as I know, the seal hasn't changed since then. I wonder if the change had something to do with availability or function or performance with the 3 different calibres.

Cheers,
Todd

Free Power Modification

I did a bit of shooting this afternoon with the P17 and the seals are working fine. Velocity was quite consistent but about 11 fps slower than my HW40. Just for fun I shimmed the P17 breech seal with dental floss and velocity jumped 13 fps. Velocity is consisent too.

Shimming the breech seal is simple. I used a small screwdriver and wound 4 turns of floss around the shank. Then I slipped the floss onto the breech seal stub. This trick will tighten the junction between barrel and seal.

Cheers,
Todd

Help needed! Where you guys buy all this o-rings? I need #117 for my HW-40, where to find it?
Thank you!

_________________
HW30s - HW50s - HW97k - HW45 - HW70 - FWB300