Air rifle piston polishing

[Fudgeisbest]

Why when trying to improve the performance of a spring piston air rifle do people feel the need to polish the piston.
Is it not true that the only part of the piston that is in contact with the Cylinder is the seal.

[bighit]

Not sure if it happens on all airguns but the rear of the piston in my HW99S scored the cylinder on cocking. . I suspect other HW models do it.

Piston in a drill and polished with emery paper.

Bumslide or other moly grease on the rear of the piston.

[Fudgeisbest]

Not sure if it happens on all airguns but the rear of the piston in my HW99S scored the cylinder on cocking. . I suspect other HW models do it.

Piston in a drill and polished with emery paper.

Bumslide or other moly grease on the rear of the piston.

in that case would it not be better to coat the rear of the piston with ptfe spray.

Thanks for the reply.

[junglie]

in that case would it not be better to coat the rear of the piston with ptfe spray.

Thanks for the reply.

no
i've tried it moly grease or dryslide preferably for me everytime.

[bighit]

in that case would it not be better to coat the rear of the piston with ptfe spray.

Thanks for the reply.

Not tried PTFE spray on mine

Moly or bumslide only . As Junglie said above.

[Mach 1.5]

The end of the piston was also polished back in the day as under cocking this may well come in to contact with the cylinder. There is no need to polish the entire piston. Mach 1.5

[TonyL]

Welcome to the forum, Mr Fudge.

I always polish the piston (by hand, with rag and Solvol) just because it seems the nice thing to do and looks much prettier. Then a small dab of moly paste around the tail / bearing surface and the tiniest trace around the edge of the seal. Then, once the piston is pushed home, a more liberal application of moly grease around the circumference of the cylinder, behind the piston.

[evert]

Is it not true that the only part of the piston that is in contact with the Cylinder is the seal.

Usually not. The piston skirt is in contact with the cylinder in most guns, and on some guns you will see wear marks on other parts of the piston too, indicating metal-to-metal contact between the piston and the compression area of the tube.

Howewer, polishing is usually not a good solution, creating bearing points of other materials than steel is the way to solve the issue.
Good lubrication helps, but cant really replace good bearing materials.

[Shed tuner]

yup, resr skirt also in contact, during both firing and cocking strokes.. this is why some guns, and some aftermarket tunes, have a rear synthetic bearing on the rear skirt, or synthetic buttons.

As said, no point polishing anything other than the rear section of the piston, unless it's out of true, in which case sort it in a lathe...

[MartinJG]

Why when trying to improve the performance of a spring piston air rifle do people feel the need to polish the piston.
Is it not true that the only part of the piston that is in contact with the Cylinder is the seal.

In my Venom tuned 80 they polished the rear half of the piston not all of it