Rekord trigger fault on HW50

[Scubashot]

I would appreciate some suggestions to cure a fault that has just appeared on my wife's HW50.
To set the scene: several months ago I replaced the Perfekt trigger unit with a Rekord unit and installed a Tinbum guide set to cure the twang. The original spring was retained and the guide length adjusted to match latch rod as per instructions. The Rekord safety catch was omitted as the rear block is not machined to accept it. All was fine and several hundred pellets have been fired since.
I have been shooting it today and noticed that the first stage travel is not behaving normally. After cocking the action the first stage works against spring pressure as usual but if I release the trigger blade rather than taking the shot, the spring pressure has gone, leaving the blade "floppy". I can still take up the slack to the second stage and fire the gun or I can re-cock it which restores the spring pressure.
After a little research I thought that adjusting the rear screw clockwise to apply more spring pressure to the lower sear should resolve the problem but it didn't. As expected it just made the trigger heavier.
If I remove the trigger unit it all works fine. The fault only seems to manifest itself when the mainspring load is applied to the trigger. If I break the barrel and use it to partially relieve the load on the trigger, the first stage pressure is restored.
I also have an HW77, so I can try substituting triggers but I don't really want to get into that if somebody out there already knows the answer.
In anticipation....

[Artfull-Bodger]

!
if you want to go very light you need to strip the trigger and polish the bottom of the sear where the trigger rollers run on it, this sounds like a bit of binding in the sears, possibly against the housing pop it out and have a look.

[Artfull-Bodger]

theres a diagram of the trigger here - http://www.airgunstocks.com/articles...r-service.html

the spring pushes against the first sear so if the trigger is floppy then the sear is sticking, usually increasing the spring weight cures this but if you note on the diagram where the blue circle is above and behind the blade, this shows the sear points which probably need a polish.



(apologies for edit)

[u.k.neil]

It could also be that the spring is tight in the trigger housing. I had one like this the other week. To cure it I ran a 3.5mm diameter drill through.

Neil

[TORNADOS7]

If I remember ritely I had the same issue on my '95k' once, pretty sure the weight adjuster screw behind the trigger blade had worked itself loose...

[TonyL]

All good advice up above.

Also :- If not already done, remove the trigger unit, de-gunk it of factory grease (I use GT85 and a small brush and cocktail sticks), dry and lube with light machine oil.

Are the trigger guard screws too tight? Particularly the rear one.

Check that the front of the bottom sear isn't snagging on any of the woodwork. A small file will cure that, especially if the unit has come out of an earlier gun, which will have a longer bottom sear. Relieve a little of the wood or you could shorten the front of the sear slightly to give the necessary clearance.

[Scubashot]

Thank you one and all for your input!
Problem now solved with a combination of your solutions.
I stripped out the trigger unit and realised that the problem must lie before the lower sear to rear sear contact point. So I removed the trigger blade and cleaned up the trigger first and second stage to lower sear contact points. I removed the trigger weight screw and spring. After cleaning and freeing up the spring I reassembled and adjusted the unit until I had a satisfactory first and second stage operation.
The rifle is now back together and working fine.
Thanks again.

[deejayuu]

If it re surfaces then suspect as post 6 TonyL's last comment. The head of the sear engagement screw can foul, the woodwork, as it moves through it's arc. Very hit and miss so relieving the clearance at the trigger slot will sort it.
Laying the rifle upside down with trigger guard removed then operating the trigger shows just how tight the tolerance is.
Just slackening and re tightening the stock screws can cause it to come and go. Look at excessive screw length on this one.

[Scubashot]

If it re surfaces then suspect as post 6 TonyL's last comment. The head of the sear engagement screw can foul, the woodwork, as it moves through it's arc. Very hit and miss so relieving the clearance at the trigger slot will sort it.
Laying the rifle upside down with trigger guard removed then operating the trigger shows just how tight the tolerance is.
Just slackening and re tightening the stock screws can cause it to come and go. Look at excessive screw length on this one.

Thanks for that!
I did check the internal surfaces of the trigger cutout in the stock but couldn't see any rub marks. I wrapped a piece of sandpaper round a file and cleaned it up to be sure as well.
If it stops raining I will go and put some pellets through it to ensure that it is well and truly fixed!