HW97 Spring in a HW95?

[Thegreg]

This question is purely to understand any compatibility issues, not as an upgrade!

Basically I recently bought a used HW95 with a new HW mainspring fitted. When I stripped it down and measured the spring, it didn't match the dimensions of a HW95 standard spring, but was a perfect match for the HW97/77 spring dimensions. It looks like a 97 spring has been fitted into a 95.

Despite the larger O/D it's not overly tight in the piston liner, if anything it's quite an ideal fit. It's making good figures on the chrono so no issues there.

The thing is it's a very loose fit on the spring guide/top hat made for a standard HW95 spring, and is very twangy as a result. Before I go to the bother of making a set of guides to suit, has this been done before (for whatever reason) and were there any adverse effects by doing it?

I'm sure the guns are fitted with different diameter springs for a reason, otherwise I guess they'd have standardised them.

Cheers
Greg

[TonyL]

As far as I could tell, there wouldn't be any compatibility issues. If the spring fits the innards "generally okay", the power output is to your liking, condition of the spring is good and the cocking and firing cycles (apart from the twang) are okay, it'll be fine. Many springs from different guns have been successfully re-purposed on other guns. Looking at the specs in the Mainspring Data Thread, they're very, very close anyway. And I'm sure Tinbum once posted a few years ago saying that HW seemed to be fitting the same springs in a fair few different models. Go ahead with the guide and top hat.

[evert]

The 77/97 springs obviously seem to have a tendency to turn up as 95/98 springs.
When I bought my .177 95 from Germany in 2009, it came with a 7,5joule spring fitted, but I had ordered a full power spring with it.
That spring had the 14,2mm ID of the 97/77.
When I recently ordered a 95/98 spring from Knibbs, they sent me the same 14,2mm ID spring, so it seems this is accepted.

However, HW95's with the full power (no power restrictions here in Norway) 95 spring seem to me to be less "noddy/bouncy" during firing than those with the full power 97/77 spring.

[BTDT]

Going by the Versandhaus figures in the mainspring data thread, the HW97 mainspring is around 92% of the rate of the stiffer HW95 spring, but 20mm longer, so the 97 spring in the 95 will give slightly gentler recoil acceleration, a little less surge, and be slightly more energy efficient.

[Thegreg]

Thanks for the replies chaps, much appreciated.

It seemed odd to me that Weihrauch would produce such similar (and seemingly interchangeable) spring types rather than standardising them, unless there was a good reason for the differences.

If that reason is just very minor differences in performance characteristics then I'm happy to crack on.

Cheers
Greg

[PCPShooter]

I think a lot of stuff airgun makers do is a lot less calculated / carefully considered than imagined ......

I'm sure HW want to get stuff right, but they didn't worry too much about lopping springs a while back.

Maybe they are moving towards 'A' uk spring that fits the 26mm guns _ thing is most makers never admit to any problem, though don't HW say 'continuing improvement' or some such

Fair enough - they are the top springer maker all said and done and make great gear. They make less bloopers than anyone else lol ! No one gets everything right all the time - imagine trying to design loads of springs for differing rifles going to different countries with different legislation - Jeepers !

[robs5230]

The best results I've had with a 95 are with the 97 export spring. 20.5od, 3.1 wire, 14.3id

Yes you'll need new guides, and still likely need a piston sleeve, but its a hell of a spring.

Coincidentally, its the same spring that I used in the new model Sport, and countless other rifles.

The only source available for us in the UK, is Tinbum.
Hull cartridge claim not to recognise this spring, and the spares companies don't list it.