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 Post subject: New air rifle woes.
PostPosted: Fri Dec 30, 2016 8:01 am 
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Joined: Tue Nov 01, 2016 5:59 pm
Posts: 88
Location: Dryden,Ontario
Hi everyone new here.I just thought iI would let people know of my issues involving a new gun.I really wanted a Shockey Steel Eagle in .22.I could not find a full power version of this gun in Canada.I am not a fan of the thumbhole stock but wanted the NP2 platform.After searching various forums on Canadian detuning methods I was confident in my abilities to correct the detune.ie longer piston I have access to metal working tools so accurate cutting and drilling not an issue.hole in piston have been welding for over 30 yrs so plugging hole was a 10 second fix.weaker gas spring a simple new replacement part.It all seemed like it would be easy.Got new gun took apart had short piston with hole drilled in it.plugged the hole only gained 30 fps around 480.took gun apart changed the seal even though oem looked good put in a NP214-012 full power gas spring.bumped fps to 600.I checked every thing several times same results.Discovered transfer port seems larger than normal.In my searching I read that .125-.135 is optimal size for transfer ports on guns in this class,mine measures at .160.Moral of story buy a full power gun and buy different stock would have been easier with better results.


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 Post subject: Re: New air rifle woes.
PostPosted: Fri Dec 30, 2016 1:32 pm 
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Joined: Tue Nov 01, 2016 5:59 pm
Posts: 88
Location: Dryden,Ontario
Well I just put another 100 pellets through.Ten 10 shot groups @ 35 ft.Smallest group was dime size,largest was 3/4" if you discount a couple flyers.It has settled to 560 fps.thinking about putting weaker gas spring back in.The extra cocking effort does not seem worth only 80 fps


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 Post subject: Re: New air rifle woes.
PostPosted: Fri Dec 30, 2016 1:48 pm 
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Joined: Sun Jan 09, 2011 8:07 am
Posts: 3320
Location: Central West River Nova Scotia
The dia of the TP is one of the biggest factors for air gun power. I made a thin washer and drilled the hole smaller than oem and it gave me 60 fps increase in a Qb 57. A thin washer inside the compression tube of a springer, does not impede performance. Start small and slowly increase dia, till you find the sweet spot. The problem is tearing everything apart everytime you want to enlarge the hole.

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 Post subject: Re: New air rifle woes.
PostPosted: Fri Dec 30, 2016 1:55 pm 
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Joined: Fri Dec 30, 2016 1:45 pm
Posts: 31
Location: Muskoka
Sorry to hear that!

I am re-tuning a boxing day MTR 77 NP myself, have yet to fire it in any condition, basically just plugged the hole and de-burred everything I could reach (crazy burrs!!!! How do they get a piston seal in there intact?) and gave it a smidge of silicone grease.

The stock NP on this thing is crazy; can't budge it by hand... extreme cocking effort with the short barrel.

The hole in piston seems like the worst detune method. Seems like it would invite piston slam.

There are some fixes for an oversize transfer port. Joe's sounds simple (new to me- I was going to suggest drilling, tapping , insert) but doesn't deal with dead volume... still, he has data.

I wonder if this should be in mods/repair...


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 Post subject: Re: New air rifle woes.
PostPosted: Fri Dec 30, 2016 3:17 pm 
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Joined: Tue Feb 18, 2014 7:24 pm
Posts: 684
Location: Dowling ,ontario
Is it possible crosman /Benjamin is using an oversize transfer port to detune now? That would be a new one . At least not that I've heard of .

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 Post subject: Re: New air rifle woes.
PostPosted: Fri Dec 30, 2016 6:15 pm 
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Joined: Sat Dec 17, 2011 10:04 pm
Posts: 538
Location: Komoka Ont.
One method of reducing the transfer port is to use thin wall brass tube with 1/8" inside diameter which apparently can be found at modeling and hobby supply shops. Then the TP can be drilled out to fit the tube and secured with JBweld.

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 Post subject: Re: New air rifle woes.
PostPosted: Fri Dec 30, 2016 9:34 pm 
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Joined: Tue Nov 01, 2016 5:59 pm
Posts: 88
Location: Dryden,Ontario
Thanks for the ideas.I do really like this gun.i put about 700 pellets through since dec.25 and if i get my hold right it is a tack driver at 35ft.Was dissappointed with the fps but is probably ok for small pest control.i think i will try the small washer idea though sounds easy enough without major drilling or tapping.


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 Post subject: Re: New air rifle woes.
PostPosted: Fri Dec 30, 2016 9:55 pm 
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Joined: Tue Nov 01, 2016 5:59 pm
Posts: 88
Location: Dryden,Ontario
Hobbyman2007 wrote:
Is it possible crosman /Benjamin is using an oversize transfer port to detune now? That would be a new one . At least not that I've heard of .

I have not heard of this either but transfer port did not get .030 larger by itself.Mostly put this on to help others avoid same problems.


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 Post subject: Re: New air rifle woes.
PostPosted: Fri Dec 30, 2016 10:11 pm 
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Joined: Tue Nov 01, 2016 5:59 pm
Posts: 88
Location: Dryden,Ontario
I have removed the fake suppressor and shortened shroud to end of barrel much harder to cock now that the barrel is 6 inches shorter


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