anyone care to share your ideas.

If you have a lathe you can chuck the piston, with the seal and touch the seal, with a file or 400-600gt paper. I'm you could do the same by putting the seal on a bolt chucked in a drill.

Craig,

I saved this information I found on JM's site (can't remember where on the site it was):


First take the new seal unmodified with some moly
paste or Webley seal oil and put the new seal in
the gun. ( I do not even put the action back in
the stock, saves time and if your careful it's not
a problem. However I have been doing this for 25
years-so do what your comfortable with.)


Next fire 5 shots to set the seal. Chrono it and
see where its at. If it's where it should be-leave
it alone. If not remove it from the gun and it
will show you a dark line just at the front edge
or just behind it. Use an abrasive cloth (180-220 grit) to make this mark disappear. ( test it in the
compression tube a few times to see how it feels)
When its snug and not loose or too tight then put
it back in the gun and fire a few shots to settle
it in. If its close to where it should be, leave
it alone as it will pick up in power down the road.


The seal can be sized on a lathe or in a electric
hand drill or using a dremel tool if super
careful. (Or just by rotating it in your hand
against the abrasive-best if fitted to the piston.
Keep the natural seal contours as they are)You
should get a semi gloss edge on your newly sized
seal. This material sizes super well and very
little effort is required.


http://www.airguns.citymax.com

good info J.
how about seal damage due to over heating, i was talkin with Eddie the other day about rapidly firing an A/G.
when i break in a fresh tune i usually rip a whole tin thru it in one sitting.
he was sayin that the heat build up from repeated firing will cause damage to the seal.
does anyone have any experience on this.

If you have a lathe you can chuck the piston, with the seal and touch the seal, with a file or 400-600gt paper. I'm you could do the same by putting the seal on a bolt chucked in a drill.

i do it by hand with the seal on the piston.

I usually go through about 500 (sometimes up to 1000 a day) at a time myself and have never experienced a damaged seal from shooting that much at a time (at least not with JM's seals). It's tough for me to tell with factory seals since they've always come out a little buggered...

I too have always hand fitted it with the seal on the piston, just as I would most other parts. Insert, sand, reinsert, sand, etc. A little moly like what JM describes helps me to see the contact points.

when i look at a used JM seal under 10x magnification i can see wear on the seal.
i was thinkin it was the hone job i was doin, i was thinkin about honing to 600 grit instead of 400 grit to see what the difference in wear to the seal would be.

I'm still waiting to get some shots on a seal more slowly then usual to see if this helps with the wear.

On my personal airguns and a few tunes, I break the freshly honed
cylinder in with an old or cheep seal and then fit the Tesla or Apex
seal by hand.

so your sayin you install an old seal then shoot it then install the new seal.
very interesting.

I wonder if there would be any benefit to using an old seal with a little lapping/abrasive compound on it first to run it a few times back and forth through the tube... I may order a bunch of new crosman seals just for fitting/testing. Anyone know how much they sell them for?

IIRC, there $1.70ea.

newbie primer, again... are the apex seals made out of a better stock than the factory? When I replaced my original seal in the Storm, it looked to be a similar material (although there were SIGNIFICANT shards of metal embedded in the seal from the factory).

not only are JM seals made from better material but they are better in design as well.
notice the relief groove is deeper in the JM seal, which allows for better sealing.

I have put the seal on a 10mm counter sunk
cap scew with a washer/nut then put it in
the drill press and spin it as fast as yer can
useing 400grit paper.

Jon:

My last purchase of Crosman springs and seals was six to eight months ago.
Part No's:
# 02 C1K77-002 Piston Seal (B18-01-1A) . . . . . . $3.60 ea.
# 08 C1K77-008 Breech Seal (B12-00-14)("o"-ring at the breach) . $1.00 ea.
# 10 C1K77-010 Piston Spring (B19-00-4A). . . . . . $5.70 ea

They have a flat rate shipping charge of $4.00 per order. Seems quite reasonable to me.

CW's technique of using an old seal to lap the compression tube bore is excellent.

All abrasives create peaks and valleys. They may be small, but those small peaks can still be sharp. Lapping with an old seal smooths or dulls the sharpness of the peaks thereby reducing the wear the new seal get during its its initial break-in. The old seal will also pick up residual grit, both abrasive and metallic. Thus, the new seal will "seat" more quickly and without the wear it would suffer otherwise.

While we're on the subject, those aforementioned valleys hold lubricant. A urethane seal like a Tesla or Apex is not porous like leather and absorbs very little if any lubricant. That is why a 600 or higher grit finish will work for a compression tube where a leather seal is used but NOT for a urethane seal. A 600 grit groove/valley is too small to hold adequate lube for urethane seals.
Bob Werner covers some of this in library articles on his sight but does not adequately explain why - he may not really know. I suspect most of his information came from Paul Watts and Russ Best.
Cardews' book also covers some of this.

Hope this helps,

Amigo

Very true. Also, with the Apex and Tesla seals, moly
must be used, by it self or in conjunction with the lube
of your choice. I alway burnish (work into) the cylinder
with some Molygraph and then wipe it out clean.
Moly will be left behind, bonded onto the surface of
the metal.

Once the moly (molybdenum disulfide) is bonded to
the surface, it cannot be easily removed and actually
has to be machined off.