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 Post subject: Low muzzle velicity
PostPosted: Wed Feb 22, 2012 9:17 pm 
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Joined: Wed Feb 22, 2012 8:50 pm
Posts: 5
Location: Toronto Canada
I recently bought a late friends Crosman Phantom 500 .22 with a 4x32 scope. I decided to test it out at a couple of empty cans at a range if about 45 feet.

First thing I noticed was that it had a odd sound when fired (spring like noise, though no real shock as it is a spring fire after it all)

The other thing is every shot, 20 in total, either hit the backstop 2 - 3 feet below the target, or further, into tbe ground, 3 inches infront of the backstop.

I talked to his widow who told me that it had only been fired aprox 20 times prior and that it had been stored in a hard case for a while, though she did not say how long.

Any suggestions on what the problem(s) is/are?


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 Post subject: Re: Low muzzle velicity
PostPosted: Wed Feb 22, 2012 9:25 pm 
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Joined: Fri Jan 22, 2010 1:17 pm
Posts: 4146
Location: Kingston, ON
Sounds like a broken spring. You should tear it down and see whats going on inside.
here are some video tutorials
http://www.youtube.com/watch?v=TTr0jfVb ... ature=plcp
http://www.youtube.com/watch?v=AFThRvTI ... re=related
http://www.youtube.com/watch?v=J0Drq6hD ... re=related
http://www.youtube.com/watch?v=tHd44bXU ... re=related

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 Post subject: Re: Low muzzle velicity
PostPosted: Mon Feb 27, 2012 4:33 pm 
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Joined: Wed Feb 22, 2012 8:50 pm
Posts: 5
Location: Toronto Canada
Ok, I was able to strip the phantom down and thankfully, the spring was NOT broken.

There was however, a fair amount of debris. Looks to me like metal fragments. I cleaned everything I could, inside and out verifying there was nothing left in the chamber, filed down any rough spots I found and sanded the piston lightly.

I however forgotten to make sure I had everything I needed. In this case, Moly Grease. As my local Canadian Tiress stores did not have any in stock, I decided to go with what I though was an acceptable substitution. MotoMaster Moly Extreme Pressure Grease.

So after cleaning everything again to be sure there was no dust or debris, I greased up the appropriate pars, making sure not to over do it.

After a brief struggle to get the spring and the other internal parts back into the chamber (and having to take the cap off again as I forgot to replace the trigger block BEFORE I closed it up) I reassembled the rifle and fired off a couple of test shots.

No more TWANG or rattling spring noises, though I have yet to be able to get a proper test in.

All I need to do now is find someone local with a chronie so I can perform a proper test shoot.

Thanks for your assistance.


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 Post subject: Re: Low muzzle velicity
PostPosted: Thu Mar 01, 2012 6:59 pm 
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Joined: Wed Feb 22, 2012 8:50 pm
Posts: 5
Location: Toronto Canada
Ok, seems I may have ahem jumped the gun when I said things were working alright. the rattling spring noise is gone, but velocity is still in the crapper, pellet dropping after perhaps 30 ft or so. I am thinking of striping her down again reclean, lube and reassemble, but I am not sure if it will help any.


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 Post subject: Re: Low muzzle velicity
PostPosted: Thu Mar 01, 2012 7:26 pm 
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Joined: Thu Sep 22, 2005 2:40 pm
Posts: 6371
Location: Eastern Passage N.S.
Mine did the same after about 200 shots and it was a bad piston seal in mine .
It was ok for a while with a new piston seal then failed again after about 100 shots,
now I am on my 3rd seal .

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 Post subject: Re: Low muzzle velicity
PostPosted: Thu Mar 01, 2012 8:30 pm 
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Joined: Wed Feb 22, 2012 8:50 pm
Posts: 5
Location: Toronto Canada
under500fps wrote:
Mine did the same after about 200 shots and it was a bad piston seal in mine .
It was ok for a while with a new piston seal then failed again after about 100 shots,
now I am on my 3rd seal .


Hmmm I didn't see any wear on it when I had it open before. Looks like I am going to have to strip it down again after all and make sure I get a really good look at the seals..


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 Post subject: Re: Low muzzle velicity
PostPosted: Thu Mar 01, 2012 8:37 pm 
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Joined: Sun Oct 04, 2009 7:44 pm
Posts: 1279
Location: Longueuil
Jester1969 wrote:
under500fps wrote:
Mine did the same after about 200 shots and it was a bad piston seal in mine .
It was ok for a while with a new piston seal then failed again after about 100 shots,
now I am on my 3rd seal .


Hmmm I didn't see any wear on it when I had it open before. Looks like I am going to have to strip it down again after all and make sure I get a really good look at the seals..

problem with those guns is the finish of slots and holes in the main tube, i would debur all the holes and slots just to be sure i dont break the new seal .

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qb78 .177
crosman phantom .177 , Rex 2-6x28 (thank to lauchlin)this scope has died 02-02-2012
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crosman mk1
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