Renovating a springer. HW77 this time. Supportive opinion please.

[deejayuu]

After much reading up on here/elsewhere, and the stock finished, work starts on the internals. 25mm, .177 cal.
The basic clean and polish of contact surfaces done including trigger.
Now need to get it working well with replacement bits where needed.
So things learned so far;
The piston seal fit seems too tight so re sized an old one till the piston falls under it's own weight.
Immediate increase in out put of at least 50 ft/sec.
Many alternative springs available which fit or will with some work but care needed to avoid overheating.

So questions;
To fit a spring suggested by helpful forum pal a new guide is needed so made one full length to give more/better spring support along the stroke. Is this a good plan? Why are standard so short even with top hat?


When cocking there is noticeable interference as the latch rod enters the trigger block. Is it sensible to taper the
rod end? Avoiding the engagement faces of course. [img]http://i.imgur.com/9brmeGg.jpg[/i


The spring guide dia. is easily threaded say M14/1/4G to fix direct to the trigger block so dumping the awful
flared petal end. Is it worth the effort?
Piston/guide rod will be sleeved to snug/sliding fit where needed.

Some of radial needle roller thrust bearings are spare has anyone used them as spring seat? or would you?

Using 7.3 gn pellets the ME is considerably higher than 8.3 gn . Does this sound right? Will be setting to 10 ft.lb. with 8.3 gn to be comfortable and that's plenty for my needs.
Thanks for looking. Any/all support welcome. be gentle 'cos I don't yet know where I'm going.

[Phil Russell]

Seems to me you pretty well know what you are doing and I am sure people far more competent than me will give expert advice. Your comment about interference when the latch rod enters the trigger block is interesting ... does this suggest the latch rod is not running true? If so, can it be 'centralised'? I remember a comment by UK Neil in one of his stripdowns that he came across an out of true latch rod and corrected it (not on a 77/97 I think) by mounting the piston in a lathe chuck and tapping the rod to get it right. I have never seen an out of true rod that catches the trigger block.
Personally I turn up delrin guides and top hats and use steel slip washers when needed for the spring end faces. I never bother with threading guides to secure them to the trigger block ... but everyone to their own ...
Interesting comment on bearings ... what sort / size / where from. (the bay reference?). I have seen various comments suggesting needle roller bearing are not worth it / not up to the pressures involved etc. But I have no personal experience of them.
Cheers, Phil

[magnummike]

Is the rifle at Dave's Jules , I'm popping up to see him tomorrow , I think all that's needed with the 25mm 77 is a Polish and debur correct fitting guide and top hat , my 25mm 77's shoot much nicer with a longer softer spring Atb Mike

[TonyL]

Seems to me you pretty well know what you are doing and I am sure people far more competent than me will give expert advice. Your comment about interference when the latch rod enters the trigger block is interesting ... does this suggest the latch rod is not running true? If so, can it be 'centralised'? I remember a comment by UK Neil in one of his stripdowns that he came across an out of true latch rod and corrected it (not on a 77/97 I think) by mounting the piston in a lathe chuck and tapping the rod to get it right. I have never seen an out of true rod that catches the trigger block.
Personally I turn up delrin guides and top hats and use steel slip washers when needed for the spring end faces. I never bother with threading guides to secure them to the trigger block ... but everyone to their own ...
Interesting comment on bearings ... what sort / size / where from. (the bay reference?). I have seen various comments suggesting needle roller bearing are not worth it / not up to the pressures involved etc. But I have no personal experience of them.
Cheers, Phil

Pretty much as above and, as Phil says, you seem very capable.

I, also, have seen some references to the piston rod not being central on some guns, so worth checking.

If it was okay, would it be worth considering chamfering the entry to the trigger block rather than the rod?

Bearings....quite a few have tried the bearings on the rear end and report good results. Others are happy to use plain polished steel washers or synthetic ones. As long as the spring ends are flat and smooth and they have a nice flat and smooth surface to spin on, all will be good.

Just a small note on the home made longer spring guide...I assume you have replicated the as standard, flared out ends for ease of fabrication and so you can simply use tube? But that flared end is one feature of those standard older guides that many don't like and even the factory use nylon ones now. I suppose that, as long as you are then employing nice, smooth washers over the end and that all surfaces are nice and smooth, it will still work well. Machining one from steel with a nice flat end would entail much more time, but worth it in the end? The other option would be to turn one form Delrin...many advantages...cheap, reduces metal to metal contact and would also reduce any potential resonance. But, ultimately, not as strong as steel, although there are lots of guns out there that have run reliably for many years on synthetic guides. Down to personal choice.

[p.j.]

Good idea to lose the petal shaped guide they are truly terrible. I have a HW77 with the guide fitted to the back block - an early Venom trick. I cant say its any better than a good fitting synthetic guide. Can be limiting if you want to fit different springs.

[deejayuu]

Great response as expected. I may appear to know what/how to do but really struggle to know why/when.
Phil.
The bearing come from things I've tripped over time. Can't throw anything away. Readily available via fleabuy as roller or ball.
Latch rod fouling is due to sloppy fit of guide flare in main tube so mis aligns with block.
Mike
It's back home now but will take it to the Mole when this bit's done so will keep you informed. At the mo' spring is Titan 5 cut to 25mm pre load. It has a
rate around 30 lb/inch, so not high rate, giving 740 ft/sec with 8.3 gn and 840 ft/sec with 7.3 gn. I have a 26 lb/inch and 20 lb/inch to try as well.
TonyL
With you all the way especially time consuming turning from solid. Ha, ha, in my case more time than I've got left with a file and pillar drill.
The flare is a temporary fix to try different spring the Mkll will end plate will be weld/screw/interference fit 'cos, to me, there's no real stress at that point.
Resonance (if that means twang/bounce/slam??) will have to be approached via damping/pre load in my case.
p.j.
Good shout on spring change flexibility. Thanks.