hw35 tuning woes

[copperjacket]

After many attempts tuning my 30 year old leather piston washered HW35 using the excellent advice contained on this forum, I have happily been running it for the umpteenth time - the latest reason being the replacement of a snapped mainspring.

This item was one supplied in a tuning kit in the 80's along with Cardew's tuning book yet being honest the gun has never lived up to expectations. The new spring is a standard secondhand Weihrauch item kindly donated by Airgun God. In addition I have now radiused/deburred the transfer port and fitted a plastic sleeve to the inside of the piston together with Delrin Top Hat and Guides supplied by chambers.

The rifle is shooting very sweetly: The horrific twang and erratic grouping have been replaced with a very good grouping but it seems the rifle is well down on power despite having around 2-300 pellets through it since the last rebuild and approximately 1600 shots since the Piston/cylinder/washer etc were tuned.

The leather piston washer was sized so that the piston just falls under its own weight unless the transfer port is blocked.

I don't have a chronograph and the power has only been compared to a 30 year old Mercury also in .22. The comparison is very unscientific: Using a variety of pellets at 10 metres into a steel pellet catcher, the pellets from the Mercury are always significantly more flattened than those from the HW35.

The Mercury is completely untouched and I am forced to conclude that the HW35 is producing a lot less than 10ftlbs.

Where do I go from here please?

[ikarma70]

simple answer....buy or lend a chrono.
if your hw35 is a .22 then theres a good chance it will be doing at least 10ft.lbs.

also bear in mind the hw35 weighs more so it will absorb more recoil that the mercury.

[Andy W]

Hi,
You might find this interesting:

http://www.airgunbbs.com/forums/show...t=mystery+HW35

My own '35 suffers from this.

Regards,
Andy.

[copperjacket]

Thank you both for your comments.

Andy W

I don't think I have this problem since before the latest rebuild the rifle was producing a lot more power albeit with the accuracy of a shotgun and the cylinder has not been touched since then.

Ikarma 70

Your point regarding the chrono is of course valid and I am trying to borrow one locally.

I am fairly certain however that given the poorer pellet deformation from the HW35 in comparison to the Mercury (which I believe only produce around 10ftlb's or so), that the HW35 must be producing less. I suppose the alternative is of course that I have an exceptional Mercury...

[mxgb]

Thank you both for your comments.

Andy W

I don't think I have this problem since before the latest rebuild the rifle was producing a lot more power albeit with the accuracy of a shotgun and the cylinder has not been touched since then.

Ikarma 70

Your point regarding the chrono is of course valid and I am trying to borrow one locally.

I am fairly certain however that given the poorer pellet deformation from the HW35 in comparison to the Mercury (which I believe only produce around 10ftlb's or so), that the HW35 must be producing less. I suppose the alternative is of course that I have an exceptional Mercury...

Hi Copper Jacket
Do not under estimate your Mercury, they are more than capable of spitting pellets out at 11 + ft/lbs with very little work on them
Can not help with the HW35 though as never owned one, nice bit of kit though. Can you not get a local airgun dealer to run the 35 over a chrono just to put some context into the perceived lack of power.
ATB Keith

[ikarma70]

Can you not get a local airgun dealer to run the 35 over a chrono just to put some context into the perceived lack of power.
ATB Keith

i wouldn't use a shop to test ya gun,if its over the limit they can refuse to return it to you and charge whatever they like to turn the power down.

buy or lend a chrono...safest bet.