Tuning a GP/NP gun/what to lube?

[SoCalZac]

As I understand it there's not much to tune with a GP gun other than removing some burrs and getting a nice smooth trigger. I have a Crosman NP that I tore apart and deburred. I was wondering if i put the moly paste inside the compression chamber or just on the back of the piston and a little smear on the seal?

I noticed the GP itself has a metal o-ring/clip in the rear that looks like it helps center the ram in the piston. Would making a sleeve for the rest of the piston be a good idea and if so do you leave a slot for the cocking mechanism or just sleeve the whole piston?

I already pulled the trigger apart and removed all the anodizing from where the trigger seats together/the sear. (sorry total gun newbie) should I put any moly on the trigger itself or lube it with anything? If you have any other tips for rebuilding a NP or tuning ideas I would greatly appreciate it. TIA

[UlteriorModem]

I will be watching for responses...

I dont think there would be much to gain by 'sleeving' the gas ram.

One thing of note, the Crossman drawings show the gas spring kinda backwards, the thicker part goes up into the piston. Or at least that is what has worked best for me.

[SoCalZac]

Thanks for the heads up. That is how mine came with the thick gas strut part inside the piston. Yeah I didnt think anything would be gained by sleeving by sleeving but i am a total noob when it comes to guns but am very mechanical. I was surprised at how simple the NP gun really is.

[UlteriorModem]

Yea there was another user that his gun came the same way. I took mine apart and forgot to make note of the gas spring orientation and went by the drawing. I got really bad crunchy scraping while cocking.

Frankly I think Crosman/Benjamin exploded view drawings are wrong

[SoCalZac]

That’s funny I just looked at the exploded parts view. It is backwards for sure 😂😂😂

[SoCalZac]

Giving this bump. Does anyone have any input on where I should put the moly paste or any other tips would be greatly appreciated.

[Roadworthy]

I don't believe piston orientation makes a great deal of difference.  The idea is to reduce moving mass and hence recoil.  I think if you find a midpoint and balance the strut at this point the halves work out pretty close to the same.  As far as lube, I clean my compression tube with carb cleaner or brake cleaner.  I size the piston seal for a proper fit (2-3 pounds of resistance) then  I like to burnish some moly powder into the walls of the compression tube and the piston seal.  I'll then put a bit of Krytox on the lip and sides of the piston seal as well as the sides of the piston.  I'll do the moly and Krytox thing on the cocking slot as well.  If you don't have Krytox, moly lube works almost as well.  Finally, if I have removed the barrel, I'll use moly powder and/or moly lube on the pivot and latch mechanism.  I put a drop of oil into pivot points on the cocking linkage. 

[SoCalZac]

I don't believe piston orientation makes a great deal of difference.  The idea is to reduce moving mass and hence recoil.  I think if you find a midpoint and balance the strut at this point the halves work out pretty close to the same.  As far as lube, I clean my compression tube with carb cleaner or brake cleaner.  I size the piston seal for a proper fit (2-3 pounds of resistance) then  I like to burnish some moly powder into the walls of the compression tube and the piston seal.  I'll then put a bit of Krytox on the lip and sides of the piston seal as well as the sides of the piston.  I'll do the moly and Krytox thing on the cocking slot as well.  If you don't have Krytox, moly lube works almost as well.  Finally, if I have removed the barrel, I'll use moly powder and/or moly lube on the pivot and latch mechanism.  I put a drop of oil into pivot points on the cocking linkage.

Thank you for that!! I don’t have moly powder should I put a light coating of moly paste in the compression tube of do you think just the piston will be good enough?

[UlteriorModem]

I don't believe piston orientation makes a great deal of difference.  The idea is to reduce moving mass and hence recoil.

I found out the hard way that it does make a difference. If you put the gas spring in the way the drawings show, that is the thinner metal rod into the piston, when being cocked the heavier outside part of the gas spring has to negotiate it's way into the piston.

If everything is perfectly lined up its not an issue, but... if it is not you will start scraping and grinding the thicker part of the gas spring as it moves in and out of the piston.

If the thicker part of the gas spring is put into the piston there is NO movement inside of the piston.

Sure it makes a difference in the moving mass but frankly I cant tell much of any difference, it still acts like a springer / jumper.