Airguns And Airgun DIY.

Buttoning is the addition of low friction bearings, usually plastic, to the piston to remove metal-to-metal contact between the piston and the inside of the receiver tube.
This is the unique component of a Lazerglide tune, I know of no other tuner routinely using this feature commercially. 
Be aware that just adding buttons to the piston will NOT make you gun equivalent to a Lazerglided gun Venom do a lot more that just add buttons!!
This procedure describes the work I have done on an old Anschutz 335, I’m sharing it for your information but the copyright remains mine.

Buttoning is just one component of a successful tune, it is intended to make the gun smoother to cock and fire. It is not a miracle cure; it will not reduce spring “twang” and vibration - that is largely the work of the spring guide and top hat.

How many buttons are needed?

The minimum is one at the top rear and one at the bottom front of the piston as this is were most of the metal-to-metal rubbing occurs in a break barrel or under leaver gun. If the gun has side leaver cocking them move the buttons appropriately.
Most modern rifles with synthetic pistons do not need buttons at the front as they actually ride on the piston seal.  Consequently three buttons set into the rear piston skirt at 120^o  to each other are normally sufficient. One on top and one on each side of the slot the cocking leaver runs in.

The 335 has a leather piston washer so I have chosen to fit three buttons at each end of the piston.

Ideally the button should be a press fit into the piston and the length of the plastic rod inserted into the metal of the piston skirt should be greater than the difference between the receiver tubes inside diameter and the outside diameter of the piston (ID-OD). Commonly the button would be expected to protrude from the piston skirt by half the (ID-OD) value.  Under those circumstances the button cannot come out once the piston is replaced into the tube.

Unfortunately the piston skirt of the 335 and many other guns is too thin to permit this ideal situation from being realized unless a flat bottomed hole is milled into the piston.  A consequence of this is the need to bond (glue) button into a rather shallower hole than that described above.
Another point to bring up is that the real life (ID-OD) is small, on the 335 the buttons protrude a very very small amount from the piston skirt. Something like the thickness of a piece of heavy printer paper.

Disclaimer.

It is a condition of using this procedure that it is at your own risk. Further you must accept that no other person or persons has any liability or responsibility for any loss, damage or injury that may occur for whatever reason.  The procedure may not work, the materials may be wrong, whatever happens whether it’s beneficial or detrimental it’s your problem.

Bottom line: - If it breaks your get to keep both halves!!

Legal Note.

By Law in the UK Air Rifles must not fire a projectile with more than 12 Foot Pounds Energy (FPE) unless they are held on a Fire Arms Certificate, the limit for Pistols is lower at 6 FPE. Therefore it is essential that you have the facility to test your gun to ensure that you do not transgress.

Air Rifles and Pistols should be tested regularly to ensure they are legal and to enable timely action if they are found to be over the limit.

This is not an exhaustive list; I’m only including things specifically required for this procedure.

Bench Drill. (It may be possible to use a power hand drill but it would be more difficult.)
Drill bit 4mm dia with 124^o tip. - B+Q
1/16 inch drill bit.
Dremal with sanding drum (it’s a luxury but a great time saver).
4mm diameter  Acetal Copolymer rod. – Rubberfast  or RSW
Plastic Bonding Kit. - 5 Star Distribution
The special feature of the drill bit is that its cutting end is much “flatter” that most twist drills.

NOTE.
The plastics used for buttoning (Delrin) Acetal Homopolymer or the Acetal Copolymer I used are not easy to glue. They require special adhesives that use a primer to condition the plastic prior to bonding. Normal “Super Glue” or Epoxy Resin adhesives are not adequate.

This procedure involves the use of tools including power tools and potentially hazardous chemicals including adhesives.

Ensure that you fully understand the safety implications of your use the equipment and products required to perform this procedure.
When using any equipment or chemicals e.g. adhesives comply with the manufacturers safety recommendations.
When using power tools or adhesives, be sure to use eye protection.
The piston assembly is a stressed component especially when there is no central rod and the trigger sear acts on the wall of the piston. You must determine if drilling/milling holes in to the piston will cause an unacceptable risk of the piston breaking.
After reading this procedure through to its conclusion, consider if you have the necessary equipment and abilities to safely perform it. This must include the facility to test the gun’s muzzle energy.

I strongly recommend the use of a spring compressor and eye protection when stripping an Air Rifle.

Remember work SAFE!

I am limiting this procedure to the buttoning process it’s self; I will not be including directions for polishing the inside of the receiver tube nor for lubricating the spring/spring guide/piston/receiver assembly.

Clean and degrease the piston.
Using a center punch mark the positions of the buttons onto the piston, taking care that none of the buttons will foul the cocking slot or the trigger sear. Mark 1 on top and 2 more at 120^o to the first. Take care not to bend or distort the piston. BE GENTLE.
Place the piston into the bench drills vice and tighten gently. Locate it in such a way that the first of the center punch marks is “top and center”.
With the drill set up perpendicular to the piston locate the drill on the center punch mark and drill into the piston skirt with the 1/16-inch drill, taking care not to damage any central rod if the drill goes through the skirt.

Note. It’s better not to go right through the skirt, stop just when the drill is causing a small dimple to appear on the inside of the piston.  This will save work later (I drilled right through.)

Replace the 1/16-inch drill with the 4mm drill and drill into the existing 1/16-inch holes. TAKE CARE the drill must NOT go right through the metal..
The aim at this time is to produce a 4mm dia hole with vertical sides that still has a metal bottom. Go slowly and check progress regularly.

Safety Note. Switch the drill off and let it stop before examining the work piece.

Unclamp the piston and repeat until all the punch marks have been drilled.
Repeat for the other buttons.
Using a file or stone smooth away any raised lip that may have formed around the drilled holes.
Using a half round or curved file remove any swarf or jagged edges that have been formed inside the piston around the drill holes.  This may be difficult and require patience if buttons are being fitted at the piston head end.

Wrap PVC insulating tape in a band just behind the holes add tape until the piston can just be pushed into the receiver tube. This band will be a guide for sizing the buttons.

Cut off about 1 inch of rod and put it in the drills chuck.
With the drill running using a file shape the end to the rod to a point.

It is very important that the angle of the point matches the angle of the bottom of the holes drilled into the piston.

Try the button in one of the holes previously drilled into the piston and if necessary re-cut the point, clip the end off the point so it will not protrude into the bore of the piston (were the spring is).
If the button was too tight a fit return it to the drill and thin it down a little with abrasive paper or a file
Repeat until sufficient buttons have been made (include some spares).

Note. A successful bond should be tough enough that the only way to remove a button is to drill it out or gouge it out.The key to making a successful bond is to de-grease well and keep any gaps as small as possible.
The adhesive to be used has minimal gap filling abilities.

Safety Note. This adhesive will bond skin in seconds so take care and use safety glasses.

With great care de-grease the holes in the piston head and the buttons.
Ensure that both are dry and free from contamination or dust.
Paint the pointed ends and a little way up the sides of the buttons with the “Plastic Primer”. 
Put ONE drop of Adhesive onto the prepared button.
With a twisting action push the button into the hole while keeping the button at 90^o to the axes of the piston and with its point towards the center of the piston.
A solid bond should be formed in less than 10 seconds.
Repeat until all buttons are in place, and then using the Dremal, fitted with a cut off wheel, cut the buttons down so that they are about ¼ inch long.

With the band of tape as a guide use the Dremal to sand the button down level with the band, alternatively file the button flush with the band. This will give the button the correct profile and leave it close to the correct length.
Polish the top of the button with fine abrasive paper.
Repeat the procedure for all the other buttons.
Try the piston in the receiver tube; it should be a smooth gliding fit.
If the piston is too loose drill out/gouge out and replace ALL the buttons, and replace them all as above.
It the piston is too tight a fit; slowly polish the buttons down, taking care to keep their profile correct, and testing regularly until a good fit is achieved.

Hopefully it’s now job done and the piston is running smooth and free of metal-to-metal friction. The Buttoning part of your tune has been successfully completed and once you have completed the rest of the tune the gun will be better than it ever was before.

 REMEMBER when you have the gun back together test the Muzzle Energy.

The glue is very Harry Potter; you look at it and you just know it's looking right back and thinking :-
Mmmm... Fingers I'm gona stick em!   Seriously I have never seen a more aggressive super glue.

Improvements.

Using a mill to produce flat bottomed holes would be an advantage, if I had used one I may possibly have been able to avoid using any adhesive.
Sizing/Profiling the buttons:- I'm not totally happy with the way I did it. Replacing the tape with shim steel of suitable thickness might be better.