Author Topic: Back Under The Hood Of The NPSS + Pictures  (Read 14946 times)

Offline Gene_SC

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Back Under The Hood Of The NPSS + Pictures
« on: March 16, 2010, 10:10:46 AM »


Every day when I am tuning air guns I generally shoot about 20 shots betweentuneswith the new NPSS. Yesterday after my last gun I picked up the NPSS .177 and took a few shots. Was tired but noticed she was a bit rough at bottom of cocking stroke. Felt like something rubbing. Was to tired to mess with it last night but tonight I took her down to investigate and I found something I want to share with everyone. Inside the piston of the NPSS it is machine very nicely butapparently I missed the burrs on the seer slots of the piston first time around. After my initial lube the gas ram outer housing which slides inside to main piston started to get small scratches attributing to the slight drag I was feeling. So Ichucked up the piston in the lathe and debured the slots once again and this time getting all the high spots...:) Then I run a home made hone through the whole piston to polish it up even more. Still leaving the machine grooves in place so lube would not wipe itself away.



While I was at the lathe I decided to re- machine the seal retaining nipple on end of piston. I chose the seal I wanted to use from the many JM seals I keep in stock and proceeded to machine piston to accept the seal. Worked perfect and now I had to size the seal for the compression chamber. I was able to get it right the first fit..:) Slid in like it was made for it.. Anyway I put everything back together and shot a dozen or so shots and then run her across the chrony just for curiosity sake. She was pushing 7.9 gn lead pellets out the tube at an average of 970 fps which works out to be around 16.7 fpe. That is a bit to high for what I shoot so I can just step up to a 10.5 Crosman CP and it should slow it down in the mid to high 800 fps range. As most of you know I took my air gun tuning lessons from CDT and I learned one thing and that was that you tune a springer for performance and not for FPS. A smooth cycling shooter is always a pleasure to shoot...:) End results on the NPSS is that it is by far one of the nicest shooting mid range and price range shooters I have shot so far..



Here are some pictures with some descriptions. A picture is worth a thousand words...:)

THE ONES I SLEEP WITH: BSA Lightning XL, AA TX-200, AA ProSport, BSA Ultra, HW-97K, Crosman NPSS .177, FX Cyclone, HW-30 Nicle Plated, AA-S200, Crosman Marauder, CZ-634, R-9 DG, Webley/Scott UK Tomahawk, Benji Kantana, Benji Marauder, Benji Discovery.....
....

Gene\'s Tunz n Toyz
Springer Tunin

Offline airiscool

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RE: Back Under The Hood Of The NPSS + Pictures
« Reply #1 on: March 16, 2010, 11:11:30 AM »
Gene,
Why the preferance for the seal that needed machining the piston as opposed to a seal that would match the original piston fit ?

Wasn't the NPSS originally a 1 inch seal ?

Paul.
Benji Trail NPXL 1100, Gamo .22 Whisper, Crosman 760 Pumpmaster, Crosman 66 Powermaster, Crosman .22 revolver, Daisy model 102, Daisy early Model 25.

Offline Gene_SC

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Re: Back Under The Hood Of The NPSS + Pictures
« Reply #2 on: March 16, 2010, 11:27:24 AM »
Paul, the seal inside diameter was smaller than the piston retaining nipple. Most all of JM Apex and Tesla poly seals have the same inside diameter as the seal I chose. Jim probably will not make a specific seal for the NPSS. Just not enough call for them. The only seals available for the short stroke piston are from Crosman and they are hard nylon. Nylon seals are the preference for high production air guns. They do not get damaged as bad as a poly seal would get during assembly. Since the poly seals are softer they will conform to any small irregularities in the tube. I did not mention it in my post but I cross hatched the tube as well for proper wear and lubing of polyseal.
THE ONES I SLEEP WITH: BSA Lightning XL, AA TX-200, AA ProSport, BSA Ultra, HW-97K, Crosman NPSS .177, FX Cyclone, HW-30 Nicle Plated, AA-S200, Crosman Marauder, CZ-634, R-9 DG, Webley/Scott UK Tomahawk, Benji Kantana, Benji Marauder, Benji Discovery.....
....

Gene\'s Tunz n Toyz
Springer Tunin

Offline airiscool

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RE: Back Under The Hood Of The NPSS + Pictures
« Reply #3 on: March 16, 2010, 12:40:09 PM »
Gene,
Is the NPSS bore larger than 1 inch ? Is that why you used the larger 1.150 seal of a Walter Talon ?

Paul
Benji Trail NPXL 1100, Gamo .22 Whisper, Crosman 760 Pumpmaster, Crosman 66 Powermaster, Crosman .22 revolver, Daisy model 102, Daisy early Model 25.

Offline Gene_SC

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Re: Back Under The Hood Of The NPSS + Pictures
« Reply #4 on: March 16, 2010, 04:12:58 PM »
Yes Paul, if you look at the pictures you will see that the NPSS is  1.150 " in diameter where the gamo and crosman pistons are 1". And also the Trail NP is 1" also.
THE ONES I SLEEP WITH: BSA Lightning XL, AA TX-200, AA ProSport, BSA Ultra, HW-97K, Crosman NPSS .177, FX Cyclone, HW-30 Nicle Plated, AA-S200, Crosman Marauder, CZ-634, R-9 DG, Webley/Scott UK Tomahawk, Benji Kantana, Benji Marauder, Benji Discovery.....
....

Gene\'s Tunz n Toyz
Springer Tunin

Offline Big_Bill

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Re: Back Under The Hood Of The NPSS + Pictures
« Reply #5 on: March 16, 2010, 05:14:49 PM »


Great review Gene !



It's reviews like yours and Jeff's' that keep me on the edge of my telephone seat. :-)



The more I read, the more I like :O



Whats an air gunner to do ? So many new babies, so few hands !



Bill

Life Member of The United States of America
Life Member of the National Rifle Association
Member Air Guns Addicted Anonymous
SHOOT SAFE ! - SHOOT WELL ! - SHOOT OFTEN !
Always Use A Spring Compressor ! and Buy the GREAT GRT-III & CBR Triggers, cause they are GRRRREAT !

Offline airiscool

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RE: Back Under The Hood Of The NPSS + Pictures
« Reply #6 on: March 17, 2010, 12:07:41 AM »
Gene,
Thanks.  Don't know why I thought the NPSS was a 1 incher too.  

That's the same seal I just put in the Trail XL. Good to know that after a few minutes at the lathe the extra seals I bought can be used if I get an NPSS in the future.

Paul.
Benji Trail NPXL 1100, Gamo .22 Whisper, Crosman 760 Pumpmaster, Crosman 66 Powermaster, Crosman .22 revolver, Daisy model 102, Daisy early Model 25.

Offline CaptZippy

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Re: Back Under The Hood Of The NPSS + Pictures
« Reply #7 on: March 17, 2010, 01:25:31 AM »
I had the same scoring on the gas tube in my NPSS in just about the same place.  I think this was one of the causes of the grinding I felt when cocking.  I lightly filed the inside of the rectangular slot at the end of the piston with a small diamond encrusted file (that's pretty tough steel) continuously checking to the point where you couldn't feel any drag on your finger.  Also, in my case, the cocking shoe face was mangled up (meaning the face which should be flat was not flat). The cocking arm shoe took some pretty heavy filing to get the face flat, then 340 grit emery cloth to get it smooth, then polishing with jewelers rouge. I spent some time with the round file on the concave surfaces of the cocking shoe also as they were gurred up a little also.  Lastly, I spent quite a bit of time on the cocking slot just south of the compression chamber.  The edges of the slot were sharp and the slot itself (not the edges) was really rough....looked like the surface of the moon with bumps and valleys.  I spent several minutes with a small wood sanding block (the size of a tongue depressor) and 340 grit emery cloth sanding it smooth. While it was all apart, I polished the trigger sear that snags the piston as well.  After all that sanding and polishing, I cleaned everything with de-natured alcohol.  I lubed with silicone and moly per CDT's guidance paying attention to the gas piston where the scoring was and re-assembled. I didn't sand/polish the compression chamber or the inside of the piston like Gene because they looked pretty smooth already.  After re-assembly and now after about 200 shots, I can profess that I am really happy that I took it apart and worked it over.  This is a truely fine rifle and being motivated by Gene and educated what to look for and how to fix minor problems, it's even better than it was before.  So if you're sitting on the fence debating about doing a Lube Tune on your NPSS....debate no more, tear it down and work it over.  When you put it all back together with the right lubes in the right places, you will be extremely pleased...not only that the shooting cycle is smoother and now more accurate, but that you know more about how your rifle works and what makes it work better.  Oooooh RahhHHH! Semper Fi Tom
If you\'re going to be a bear...be a Grizzly Bear

Offline Gene_SC

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Re: Back Under The Hood Of The NPSS + Pictures
« Reply #8 on: March 17, 2010, 01:49:27 AM »
One thing I must mention after reading your post back Tom. It is extremely important not to round the top edge of the seer slot. You can remove and burrs but do not put a chamfer on the slot. The trigger seer drops in that slot when gun is cocked and it needs to be square. So for you newer air gun DIY tuning please be careful in that area when de-burring the piston.
THE ONES I SLEEP WITH: BSA Lightning XL, AA TX-200, AA ProSport, BSA Ultra, HW-97K, Crosman NPSS .177, FX Cyclone, HW-30 Nicle Plated, AA-S200, Crosman Marauder, CZ-634, R-9 DG, Webley/Scott UK Tomahawk, Benji Kantana, Benji Marauder, Benji Discovery.....
....

Gene\'s Tunz n Toyz
Springer Tunin

Offline CaptZippy

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Re: Back Under The Hood Of The NPSS + Pictures
« Reply #9 on: March 17, 2010, 01:53:11 AM »
Gene, The top of the slot looked and felt good, so I didn't touch it.  I only did some filing on the inside where you could feel the sharpness of the edges.  Phewwww....glad I didn't screw something up!    Thanks for the insight!
If you\'re going to be a bear...be a Grizzly Bear

Offline Gene_SC

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Re: Back Under The Hood Of The NPSS + Pictures
« Reply #10 on: March 17, 2010, 02:18:04 AM »
Ya Tom, I just wanted to make it clear for the folks not to grind or file on that part of piston...:)
THE ONES I SLEEP WITH: BSA Lightning XL, AA TX-200, AA ProSport, BSA Ultra, HW-97K, Crosman NPSS .177, FX Cyclone, HW-30 Nicle Plated, AA-S200, Crosman Marauder, CZ-634, R-9 DG, Webley/Scott UK Tomahawk, Benji Kantana, Benji Marauder, Benji Discovery.....
....

Gene\'s Tunz n Toyz
Springer Tunin

Offline Gene_SC

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Re: Back Under The Hood Of The NPSS + Pictures
« Reply #11 on: March 17, 2010, 02:22:51 AM »
Tom you are right about how smooth the cycle is after cleaning and lubing everyting up.. And it is quieter than most springers and very solid shot cycle. One good point is that I find it not at all hold sensitive. I cannot wait till I have the time to just sit and shoot..:) This gun you could shoot all day without getting a sore arm..:)
THE ONES I SLEEP WITH: BSA Lightning XL, AA TX-200, AA ProSport, BSA Ultra, HW-97K, Crosman NPSS .177, FX Cyclone, HW-30 Nicle Plated, AA-S200, Crosman Marauder, CZ-634, R-9 DG, Webley/Scott UK Tomahawk, Benji Kantana, Benji Marauder, Benji Discovery.....
....

Gene\'s Tunz n Toyz
Springer Tunin

Offline jake

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RE: Back Under The Hood Of The NPSS + Pictures
« Reply #12 on: March 20, 2010, 05:17:45 PM »
great write-up gene!
if at first you dont succeed, re-load, kill count 2010.
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Offline LongIslandArcher

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Re: Back Under The Hood Of The NPSS + Pictures
« Reply #13 on: March 24, 2010, 08:15:04 PM »
Excellent write-up.  I got my .22 cal. NPSS apart right now because the gas ram was losing a lot of power after putting 3 tins of pellets through it, and I sent the gas ram back to Crosman for a replacement.  Yes, the gas ram was defective because cocking effort dropped down to about 10 lbs.  Normally, they wouldn't just do a gas ram swap, but the higher-up I am in contact with there, told me to send it to him and he'll take care of it.  He knows I worked over my NPSS till I was getting 1.5" groups at 65 yards, so I didn't want to chance that they'll replace my entire rifle should I send it back to them.  I'll be smoothing down the punch-outs in the piston sleeve before I reassemble the rifle.  The NPSS is an excellent rifle.  It shoots around 680 fps with 14.3 gr. pellets and is the quietest springer in my airgun arsenal.

Offline Schmidty25

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Re: Back Under The Hood Of The NPSS + Pictures
« Reply #14 on: July 21, 2010, 07:41:11 PM »
nice write up
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