Piston sleeves.

[LESS THAN FORTUITOUS KENNETH]

If a piston only needs a very thin piston sleeve, is it really necessary? Would it show a discernible improvement?

[Phil Russell]

In my experience, if you are trying to eliminate the dreaded 'boing' then most likely the answer is 'yes'. I have added thin (aka beer can) sleeves to rifles that had a distinct boing and it has cured them without packing the spring with grease (moly disulphide) ... just a light greasing needed. But at times I have found there to be not enough clearance for even a thin sleeve; it may appear OK but then binds as the spring expands during cocking. Usually it turns out that the spring is an aftermarket one with a very close clearance that makes it just passable without a sleeve. In these cases a light greasing of the spring usually cures the boing anyway.
My usual sleeve is the beer can. If there is a larger gap I will use a ptfe sleeve, 0.25 or even 0.5mm but care has to be taken that the spring does not bind when cocking. If the spring is a very firm sliding fit in the sleeve during assembly, forget that sleeve and go for a thinner one, or forget the sleeve altogether.
A good fitting spring guide can also eliminate boing but is a bit more problematic to do unless you can make your own or buy a ready fitted tuning kit.
Cheers, Phil

[peddy]

I always try fitting a sleeve, either tin, 0.3 or 0.5 ptfe. Found they make cocking much smoother and eliminates twang. I find it also helps quieten other mechanical noise on the slotted Pistons on firing aswel as eliminating the chance of the cocking shoe running on the spring when returning the barrel after cocking. A washer must be fitted to hold the sleeve in place which with the better fitting Spring eliminates the need of a top hat IMO.

[sherlock1963]

I fitted a smaller than standard spring in a TX piston and found it to be twangy. A Coke can sleeve did the trick.

[LESS THAN FORTUITOUS KENNETH]

I always try fitting a sleeve, either tin, 0.3 or 0.5 ptfe. Found they make cocking much smoother and eliminates twang. I find it also helps quieten other mechanical noise on the slotted Pistons on firing aswel as eliminating the chance of the cocking shoe running on the spring when returning the barrel after cocking. A washer must be fitted to hold the sleeve in place which with the better fitting Spring eliminates the need of a top hat IMO.

I wondered about the need for a top hat if the piston sleeve was a good fit. I think the same as yourself.

[tinbum]

I wondered about the need for a top hat if the piston sleeve was a good fit. I think the same as yourself.

Try and think of it the other way around. If the guides fit there is no twang. A sleeve is only there to stop lubricant migrating, if you're using it to stop twang its just a bodge. It'll work, the same as gaffer tape around a coolant pipe will.

[Shed tuner]

Try and think of it the other way around. If the guides fit there is no twang. A sleeve is only there to stop lubricant migrating, if you're using it to stop twang its just a bodge. It'll work, the same as gaffer tape around a coolant pipe will.

not really true... the front and rear guides will always have an unsupported section of spring between them, at least equal to the stroke. The sleave stops that unsupported section of spring rattling around on the piston insides.

I see a maxi pro "delux" kit coming...

[tinbum]

not really true... the front and rear guides will always have an unsupported section of spring between them, at least equal to the stroke. The sleave stops that unsupported section of spring rattling around on the piston insides.

I see a maxi pro "delux" kit coming...

instructions on how to make a free sleeve are on the website, I would feel bad charging for stuff I normally throw away!

[Artfull-Bodger]

not really true... the front and rear guides will always have an unsupported section of spring between them, at least equal to the stroke. The sleave stops that unsupported section of spring rattling around on the piston insides.

I see a maxi pro "delux" kit coming...

Totally agree, fit a top hat and guide to a piston with a poor fitting spring and you still get twang.

I recently bored a Webley piston out for a perfect sliding fit on a 21mm spring instead of fitting a sleeve, end result with no top hat was zero twang.

[tinbum]

Totally agree, fit a top hat and guide to a piston with a poor fitting spring and you still get twang.

Which is why I only supply the right spring.

[Artfull-Bodger]

Which is why I only supply the right spring.

Yep, all about the fit.

[LESS THAN FORTUITOUS KENNETH]

So, proper guides AND a piston liner covers all bases then!

[tinbum]

So, proper guides AND a piston liner covers all bases then!

Only if you use the wrong spring with too much grease.

(or yes if you prefer)

I prefer to keep moving mass down in most cases.

[Artfull-Bodger]

So, proper guides AND a piston liner covers all bases then!

The piston liner is necessary when your addressing a poor fit between the piston and spring, if the spring can oscillate upon firing it literally vibrates against the piston wall transmitting the horrible "twang" into the cylinder, so if your spring has anything other than a smooth sliding fit in the piston your basically adding the sleeve to take up the slack, not really rocket science but it works when changing the spring or making a new piston is impractical.

It does have the secondary benefit of isolating the spring lube from the cylinder wall somewhat, I say somewhat because short of Voerteks plastic spring sleeve your always going to atomise a little lube onto the cylinder wall as the piston unmasks the spring on firing!

Downside is , as Tin points out it adds mass to the piston, ok not a lot, but if your working to a spec any addition can be unhelpful.

If you have a good fit between spring and piston then you can argue you don't need the top hat as a slip washer may suffice, I use a top hat because it locates the torque bearing in the piston, a top hat can also be beneficial when you want to tune the piston weight, so making the hat to different dimensions or from different materials can be very useful!

So in reality it really depends on the build and what restrictions the tuner is working within!

[TonyL]

I'd say that pretty much sums it up very nicely, A-B.