Second Gamo tune in progress

[mick1]

After its Maccari spring, lubes and GRT111 my Hunter 440 shoots like a dream.  Trust me, I’m an average shot but now I seem to be printing groups roughly thumbnail size at 15 yards, shooting off hand.  I've started to give the same treatment to the Whisper X I bought recently, also in .177.  (Here I should explain that in South Africa a .22 air rifle is classed as a firearm and you have to get a licence for it.  But air rifles of calibres smaller than .22 do not require a firearm licence irrespective of power output in fpe.  Go figure.)
With the Hunter’s tune I opted to use the stock top hat and spring guide, ‘fudging’ things with a liberal application of Maccari ‘tar’.  On the Whisper so far I’ve done the de-greasing and de-burring and I have the Maccari seal and lube (same as for Hunter 440). However I’ve found the top hat an lower spring guide on the Whisper to be an even sloppier fit in the spring than is the case with the Hunter.  So I’ve decided to get top hat and lower spring guide machined locally.  Here’s where I ‘d appreciate some info from you ‘springer’ guys.

Top hat:
Stick to same weight as stock item?
Machine in brass?
Snug fit with ID of piston an ID of spring? (But what does ‘snug’ mean in this context?)
Nylon thrust washer needed? (curiously the Hunter has one but the Whisper doesn’t)
What’s the best profile for a top hat? The Hunter has a flat-top top hat; the top hat on the Whisper has a recessed top.  Curious.

Lower spring guide:
Machine in Delrin (will it hold the trigger block OK?)  or steel?
Snug fit with ID of spring?
Should I make the stem of the lower spring guide longer than the stock item, for extra support?  If so, by how much?
Thanks in advance for any advice you are able to give.
Ol’ Mick

[shady816]

I am having a hard time understanding the comment ( Machine in Delrin (will it hold the trigger block OK?) or steel?) is this a newer gamo with the entire grigger assembly made to the block and does it have the factory spring guide made to that? i'm sorry i can't answer any of your questions for my 440 has a gas ram and i don't own a whisper or any of the newer gamo trigger style.

[mick1]

Hi Shady,  On re-reading my post it's not as clear as it could be - apologies for that.  I too have a Hunter 440 and the piston, and rear spring guide and spring locating block appear to be identical to the Whisper's.  The Whisper I'm working on has a metal trigger blade and trigger parts.  What I wanted to ask is:  if the lower spring guide is machined in Delrin, and a threaded hole is tapped in it for the trigger assembly bolt, is is it going to be strong enough?  in other words, is Delrin up to the job?
BTW is Delrin the same material as Teflon, which is freely available for sale in South Africa?
Ol' Mick

[shady816]

Ya...i think i know what your talking about the end plug or spring retainer what ever it is the spring guide that is on that comes off and you reuse the steel end with all the threads and pin hole for everything and i would not dare use delrin for that piece in fear  it blowing backward toward your face when shooting. i cut one spring guide off before i realized they push out.

[speedturtle]

Cut the rear spring guide stem about 5/8" high. That will help you retain the part of the guide that has the threaded slot to accept the trigger guard bolt. Make a new delrin preload guide (having the same dimension as the original steel part but this time should be fitted tightly to the I.D. of the piston spring. Machine it is such a way that the 5/8" high stem can be inserted at the rear part of the new delrin guide. I will try to find my pic for that. I hope you got the idea. HTH.

[speedturtle]

Here's the pic link: http://i646.photobucket.com/albums/uu182/speedturtle810/Splash%20special%20airgun%20tuning%20parts/DSC00012.jpg

Posted link: http://www.airgunone.com/forums/showthread.php?t=1250&highlight=delrin+rear+spring+guide

[mick1]

Thanks for your response and the pic of the lower spring guide and spring locating block - a very neat solution.  I'm going to get 2 of these made up:  one for the Hunter and one for the Whisper.
Chris