HW77 springy underlever

[AC all day]

I presume that is a vintage slip-on suppressor held on by a grub screw (and maybe - my preference - a thin bras shim or -others - glue, loctite). It could be that it has moved a tad forward and now isn’t holding properly. Have you tried moving the suppressor back to increase the lock-up?

Spot on exactly....it is a slip on silencer.
I have given it a gentle tap and yes it does hold the underlever but iirc from previous 77s you should just return the U/L and it snuck into place....there is slight springiness in this.
Currently there is no breech seal or mainspring in this and it's springy. As said before the crown of the compression tube is slightly raised by a mm or 1.5....
I have also just looked and 25mm tubes are rare so will 26mm fit??

[T 20]

Spot on exactly....it is a slip on silencer.
I have given it a gentle tap and yes it does hold the underlever but iirc from previous 77s you should just return the U/L and it snuck into place....there is slight springiness in this.
Currently there is no breech seal or mainspring in this and it's springy. As said before the crown of the compression tube is slightly raised by a mm or 1.5....
I have also just looked and 25mm tubes are rare so will 26mm fit??

A 26mm cylinder/piston assembly will fit.

I'd try putting a pellet in the barrel but leaving it's tail hanging out then closing the lever --- if the pellet is pushed fully into the barrel it tells you if the transfer port is hitting the barrel.

If the pellet remains proud of the barrel then the crown could be the problem --- easiest solution is to machine the crown on the cylinder back.

[AC all day]

A 26mm cylinder/piston assembly will fit.

I'd try putting a pellet in the barrel but leaving it's tail hanging out then closing the lever --- if the pellet is pushed fully into the barrel it tells you if the transfer port is hitting the barrel.

If the pellet remains proud of the barrel then the crown could be the problem --- easiest solution is to machine the crown on the cylinder back.

Now that is a really clever idea!!

Thanks for that.....I'll give it a try

[Daveo]

Did you sort this?
Could it be the anti bear trap?

[FPoole]

Sounds like you are saying the end of the compression tube sticks out from the walls of the compression tube. That would make the breech area hit the end of the barrel and try to pop the under lever back out. Not sure what holds the plug in the head end of the comp. tube, but maybe it has been "modified" for a tighter lock up. Machining the end of the tube flush won't help because it's the recess for the breech seal that's hitting the barrel.

[AC all day]

Sounds like you are saying the end of the compression tube sticks out from the walls of the compression tube. That would make the breech area hit the end of the barrel and try to pop the under lever back out. Not sure what holds the plug in the head end of the comp. tube, but maybe it has been "modified" for a tighter lock up. Machining the end of the tube flush won't help because it's the recess for the breech seal that's hitting the barrel.

That is what I am trying to say.....even with the breech seal removed it still does it.....not so bad but, still pops back open.

[Bruno27]

May be try a very small piece of bluetack on the face of barrel to see if it get squashed (as metal to metal)

[bozzer]

I've been following this thread with interest ...

So there is no lead build up around the end of barrel at the breech? None on the inside/front of the action tube ( just under the area that is cut out ) and non on the actually end of the barrel?

So the end of the comp tube ( something ) hits the barrel or the front of the action tube ... even with no breech seal fitted! Do we know if it's the front of the comp tube head hitting the action ... or the inside of the comp tube head recess ( where seal should be ) hitting the end of the barrel?

The cocking link slots into the rectangular hole of the underside of the comp tube. That little lip stops it from falling out. So the back of that square part on the cocking link pulls on the comp tube to return the comp tube to the firing position as the cocking lever is returned to the firing position.

Are there any burrs on either the cocking link bit that sits in the comp tube ... or any burrs on the comp tube rectangular slot? Those links are hardened. Maybe there's some abnormality at that back end of that square bit that sits in the comp tube that needs trimming with a bench grinder. Just a tiny excess there will cause a tight lock up.

Have a look at the very end of the barrel breech. Sometimes on the very face of the barrel breech there are proud lines. I've sometimes smoothed those off to get the comp tube and breech seal giving a better seal to the barrel. I can't see them being that proud that it will cause this ... without a seal in ... but have a look.

How much ... accurately ... does the head of the comp tube stick out from the outer tube of the comp tube?

I also don't know/can't remember how that is fixed. I can't believe it's screwed in. So I presume its pinned. Either way it seems strange to think that it has been pushed forward.

I know you say you've checked but it still seems like a cocking link issue. Ideally try another cocking link. Check for burrs first on your cocking link and comp tube where the cocking link attaches.

[Geezer]

Spot on exactly....it is a slip on silencer.
I have given it a gentle tap and yes it does hold the underlever but iirc from previous 77s you should just return the U/L and it snuck into place....there is slight springiness in this.
Currently there is no breech seal or mainspring in this and it's springy. As said before the crown of the compression tube is slightly raised by a mm or 1.5....
I have also just looked and 25mm tubes are rare so will 26mm fit??

Pleased to be of help. I have 3 of them with slip-ons, and two need occasional tightening to avoid the lever dropping down when fired. The other one is glued on really tight.

T20 has given you the other necessary advice on the innards.

These are great guns.