Crosman update to the 13xx piston?

[flaircraft]

One of the mods I intend to do on my 1322 is to stuff the piston and reduce headspace.  However, the piston I have in my gun (purchased about a week ago) looks somewhat different from those I have seen in photos online.  I read something about Crosman changing the piston design recently (within last 2 years or so) but I haven't found any explanation of what exactly changed.

Could somebody explain what changed, and maybe post images showing the difference?

Also, since it's a different piston, is the modding process different?

[airsenal]

I've read they did improve the piston in material/design to be stronger, have less flex/compression in the recommended pump range (up to 10). My experience is the
newer guns can be a bit more powerful out of the box but the variables in tolerances like the older ones offers a range in 1322/1377 (10" bbl) from 10-40 or so fps
MV difference at max (10 pumps). Some guns out of the box new will dump 12 pumps with no residual air in valve - others may begin to retain a little air in valve at
8 pumps. These are easily solvable. In a bone stock new style 1322 by shimming the hammer spring a tiny bit and shimming under the pump piston rubber cup/seal
a tiny bit (bonding it in and fitting a o-ring around the pump cup resting at the end of the piston) it is possible to get 500 or so fps MV shooting 14.3 gr. pellet on 10 pumps
and 550 or so on 15 pumps. That's bone stock with no other mods.
So it is possible to have a fairly potent 13xx pistol or mini-carbine without doing all that other stuff or having it done and buying all the bling and sexy dress up stuff.
Also without opening the valve. When I discovered this I had a good laugh! Personally I prefer the factory rubber cup over flat top and o-ring piston seal. Also my interest
in pumping 20,30, 40 pumps per shot is long gone! Kept lubed that rubber cup will last many years.

[Rabbit\Squirrel Killer]

I've read they did improve the piston in material/design to be stronger, have less flex/compression in the recommended pump range (up to 10). My experience is the
newer guns can be a bit more powerful out of the box but the variables in tolerances like the older ones offers a range in 1322/1377 (10" bbl) from 10-40 or so fps
MV difference at max (10 pumps). Some guns out of the box new will dump 12 pumps with no residual air in valve - others may begin to retain a little air in valve at
8 pumps. These are easily solvable. In a bone stock new style 1322 by shimming the hammer spring a tiny bit and shimming under the pump piston rubber cup/seal
a tiny bit (bonding it in and fitting a o-ring around the pump cup resting at the end of the piston) it is possible to get 500 or so fps MV shooting 14.3 gr. pellet on 10 pumps
and 550 or so on 15 pumps. That's bone stock with no other mods.
So it is possible to have a fairly potent 13xx pistol or mini-carbine without doing all that other stuff or having it done and buying all the bling and sexy dress up stuff.
Also without opening the valve. When I discovered this I had a good laugh! Personally I prefer the factory rubber cup over flat top and o-ring piston seal. Also my interest
in pumping 20,30, 40 pumps per shot is long gone! Kept lubed that rubber cup will last many years.

Killjoy!   

[mafatone]

You know, it makes you why Crosman just didn't make a solid piston instead of the quad slotted one. Cost effective? How much could it cost to fill up those slots? $.02-$.03? Anything to save money.

[nervoustrigger]

Your point is well taken but there’s more to it than just the raw material cost.  With injection molded parts, cycle time is the name of the game and a part with more material takes longer to cool to the point where it can be ejected.  Another consideration is that thick regions can cause unpredictable geometry changes as the part cools and shrinks and the internal stresses develop.  If memory serves, the piston is a glass-filled part and that makes it more apt to warp because the fibers orient themselves in the direction of the liquid material flow...less shrink in line with the fibers, more shrink across them.  Glass fill is abrasive which means you have to build a hardened steel mold and that’s an expensive thing to redo if you get it wrong and the parts comes out warped.

So...yeah it would have been nice if the earlier generation pistons were more rigid but it’s nice to see that Crosman took the initiative to improve it somewhere along the way.

Now if they would just get their act together on their pellets...

[WyoMan]

Just conjecture, but maybe the rigidity of the piston is commensurate with how robust the other parts are. A compressible piston is an anti-self-distruct mechanism. Some other MSPs use a rubber washer on the piston or a pressure relief vent in the valve. Maybe the idea is to limit the maximum pressure so you don’t over-stress the valve securement, pivot holes, pivot pins and linkage members…?

High pressure is the holy grail of MSPs but also the nemesis. You can modify those little pump pistols to take high pressure and have a good service life… but they’re never going to be fun to pump to high pressure… imho
I've gone down the power trip road too. But the best part of it was discovering how to make them very robust (for a long service life) and very efficient with the pump effort.

Wyo

[flaircraft]

But the best part of it was discovering how to make them very robust (for a long service life) and very efficient with the pump effort.

Wyo

I agree completely.  One of the major goals of my build is to minimize pumping effort..  I will be minimizing pump headspace and incorporating a HDD to conserve air.

Hopefully Crosman's update to the piston doesn't change what needs to be done to minimize headspace.

[photoshooter]

Interesting read. I’m new to the 13xx series having only shot 2240s. Could you please explain in a little more detail about “shimming” the hammer spring and pump cup?