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PostPosted: Sat Dec 16, 2017 1:59 pm 
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Joined: Mon Feb 06, 2017 8:13 am
Posts: 156
Title says it all. My NP .22 went from 720 ->680 fps (14.3g) over the last few tins of pellets. I'll give it a little more use to see if it keeps dropping, but I assume I'll need a new gas spring.

Ebay has options if I don't mind the wait for shipping, but still around $70 plus tax. Pyramid Air is $50 US, plus shipping, for an OEM crosman NP.

Any Canadian options that won't cost me almost $100 for a $40 spring?

Thanks!

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Stoeger X3 .177, UTG 3-9x40 - 5.5 fpe
Crosman Shockwave NP .22, Hawke Airmax 4-12x40 - 16 fpe
Pumper Project .22, Centrepoint 4-16x40 - 13 fpe


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PostPosted: Sat Dec 16, 2017 2:27 pm 
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Posts: 778
perhaps ebay?

https://www.ebay.ca/itm/Gamo-old-Crosma ... 0005.m1851

I think there is a seller on this forum as well, probably the same guy on ebay.

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PostPosted: Sat Dec 16, 2017 2:46 pm 
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Joined: Thu May 07, 2015 8:30 pm
Posts: 1184
Location: Eastern Townships
Maybe this? You get a new breech and piston seal with it:

topic76887.html


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PostPosted: Sat Dec 16, 2017 3:23 pm 
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Joined: Wed Jul 01, 2009 3:23 pm
Posts: 3067
Location: Northern Ontario
Scopesandammo.com

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PostPosted: Sat Dec 16, 2017 4:13 pm 
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Joined: Fri Jul 01, 2016 7:47 am
Posts: 711
Location: Bradford
D&L

https://www.dlairgun.com/Accessories/Crosman/

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When the 425-hp "street Hemi" version hit the street in 1965, it was akin to taking an M230 chain gun to an arcade shooting gallery
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PostPosted: Sat Dec 16, 2017 10:11 pm 
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Joined: Mon Aug 08, 2016 7:23 am
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Location: Somewheres near the Atlantic
Could be also seals going or change in temperature.


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PostPosted: Sun Dec 17, 2017 8:35 am 
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Joined: Mon Feb 06, 2017 8:13 am
Posts: 156
Thanks so much for the responses. D&L looks like the winner. I haven't taken it apart to see how the seal is doing. I assumed it was the spring and not the seal since it's still consistent shot to shot, and I THINK it feels easier to cock. ScopesandAmmo selling the whole assembly (gas spring + piston + seals) is tempting too, since the current piston was a home-made hack job.

Guess I've gotta spend some more time shooting to confirm it's still dropping.

_________________
Stoeger X3 .177, UTG 3-9x40 - 5.5 fpe
Crosman Shockwave NP .22, Hawke Airmax 4-12x40 - 16 fpe
Pumper Project .22, Centrepoint 4-16x40 - 13 fpe


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PostPosted: Sun Dec 17, 2017 9:15 am 
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Joined: Mon May 26, 2014 1:08 am
Posts: 480
Location: Thunder Bay
I think maybe leadslinger has it right. Gas pistons tend to just die. Pull it apart and check your piston seal before you order anything. Cold weather can slow your gun down that much too, depending what lubricants are in there.
If you are checking velocities outside, your first few shots from a warm gun should be ok. You don't have to suck -20C air into the compression chamber too many times to cool things off in there and slow everything down.

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12 springers and a couple of pumpers.
2 lathes and lots of scrap metal.

I'm not multitasking. I'm doing something else until I remember what I was doing.


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PostPosted: Sun Dec 17, 2017 10:39 am 
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Joined: Mon Feb 06, 2017 8:13 am
Posts: 156
Shot a bunch of targets then re-chronied... Up to around 685-690.
Unless the power drops again, I think I know my problem.

My original #'s (720ish fps with 14.3's) were measured long after I thought the rifle had finished dieseling. It wasn't making that "crack", but it was noticeably louder than it is now. I think those higher numbers were helped along by some trace lubricants.

Current output, about 15fpe, seems where the air gun SHOULD be. I think the Crosman NP's are usually in the 15-18fpe range, and my piston is just a hair longer than stock, so it's a slightly shorter stroke. 15fpe is perfect for my needs, it still gives me a 30 yard PBR in .22

Thanks again for the suggestions, I'll know where to go if/when it slows down again.

_________________
Stoeger X3 .177, UTG 3-9x40 - 5.5 fpe
Crosman Shockwave NP .22, Hawke Airmax 4-12x40 - 16 fpe
Pumper Project .22, Centrepoint 4-16x40 - 13 fpe


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PostPosted: Fri Dec 22, 2017 12:49 pm 
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Joined: Mon Feb 06, 2017 8:13 am
Posts: 156
Leadslinger and Ricksplace were on the right track. Clean, lube, and new piston seal have me back to 725fps with 14.3's.

_________________
Stoeger X3 .177, UTG 3-9x40 - 5.5 fpe
Crosman Shockwave NP .22, Hawke Airmax 4-12x40 - 16 fpe
Pumper Project .22, Centrepoint 4-16x40 - 13 fpe


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