crosman nitro venom 22, low velocity

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stang

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Was using this rifle last year on gophers and it was dropping them without any trouble. This year the gophers are laughing at me, I can hit them but it bounces off.
Checked the velocity and it's down to 350fps with a 15.74gr Stoeger X-hunt.
Any advice would be appreciated.
 
stang said:
Was using this rifle last year on gophers and it was dropping them without any trouble. This year the gophers are laughing at me, I can hit them but it bounces off.
Checked the velocity and it's down to 350fps with a 15.74gr Stoeger X-hunt.
Any advice would be appreciated.
Click to expand...

Sounds like the seals or maybe o-rings are pooched. You are going to have to dig around on the interweb and find info on how to disassemble your rifle, determine what is wrong, find parts to fix it, and do so. Sorry, but I have never owned a nitro, only TX-200 and PCP so I don't have a clue, but I am sure that with some diligent searching you can find the info. I would start with Airgun Nation and info in the forums there might point you in the right direction. Hopefully someone else has more pertinent info.
 
Load a pellet, put a piece of tissue paper over the breech and fire. If It blows off you got a leak from the breech seal you can lose a bit of FPS from that.

Does it sound like a goose when you #### it? Have you tried a couple drops of 100% silicon oil to lube the piston seal? Don't use petroleum products.

Is it a Sub 500 fps or the 700?

Crosman break barrels are easy to take apart. You'll need to make a spring compressor.
 
OkayShooter said:
Load a pellet, put a piece of tissue paper over the breech and fire. If It blows off you got a leak from the breech seal you can lose a bit of FPS from that.

Does it sound like a goose when you #### it? Have you tried a couple drops of 100% silicon oil to lube the piston seal? Don't use petroleum products.

Is it a Sub 500 fps or the 700?

Crosman break barrels are easy to take apart. You'll need to make a spring compressor.
Click to expand...

It's the 700
 
A friend of mine has a Nitro piston airgun. It uses a mostly pre-compressed sealed nitrogen filled piston which is then 'charged' to full compression when you #### it via the break barrel action. If the pre-charged piston has partially or fully failed and the nitrogen has leaked out, the entire piston assembly probably requires replacement. He said inexpensive versions of a nitro system basically use a 'disposable' assembly. Some higher end versions can be repaired and re-charged. So you can check to see if there are other leaks with OkayShooter's test. It is possible the piston isn't fully releasing and maybe the silicone oil will help out as he said. Another test is to #### the firearm, load a pellet, close the barrel, let it sit for 15 minutes, then fire to see if the pellet velocity drops even more. If the results are indeterminate then try the same thing with a half hour interval. This test may or may not indicate a problem with the remainder of the rifle as well. If the pellet does not exit the barrel during the test, then just re-#### the rifle and fire to get it out. His bottom line is that the nitro piston and sleeve has probably failed and will require replacement.

https://cros man.ca/cen/replacement-parts-oem/crosman.html
 
OkayShooter said:
Load a pellet, put a piece of tissue paper over the breech and fire. If It blows off you got a leak from the breech seal you can lose a bit of FPS from that.

Does it sound like a goose when you #### it? Have you tried a couple drops of 100% silicon oil to lube the piston seal? Don't use petroleum products.

Is it a Sub 500 fps or the 700?

Crosman break barrels are easy to take apart. You'll need to make a spring compressor.
Click to expand...

Sorry for the delay
I tried the tissue no sign of leakage the tissue didn't move.
tried a couple of drops of silicone oil it brought velocity up slightly to 395fps.
It doesn't make any sound on cocking
 
OkayShooter said:
Crosman break barrels are easy to take apart. You'll need to make a spring compressor.
Click to expand...

The air rifle in question is a gas ram or gas piston airgun. As such it has a gas (nitrogen) filled cylinder rather than a spring piston to compress the air. It's like the strut that operates the back door of a hatchback.

These can leak. Some can be recharged. Others must be replaced.
 
stang said:
Sorry for the delay
I tried the tissue no sign of leakage the tissue didn't move.
tried a couple of drops of silicone oil it brought velocity up slightly to 395fps.
It doesn't make any sound on cocking
Click to expand...

So that leaves needing to replace your gas piston. As it probably has a leak. Is it a NP1 or NP2?
 
If you are looking to replace, the part required is shown in the diagram below at the yellow circle.



The nitro piston is shown below.



It can be ordered online. Apparently it's available in Canada here h ttps://crosman.ca/cen/cvw1k77np-01-00-stock-assembly.html

Pyramyd Air in the US has it and the website says it ships to Canada.
 
Finally got a new piston and changed it out, easy to do with Okayshooter's disassembly guide. I am getting very inconsistent velocity now, from 780-1050fps though, did I miss something?
 
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