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PostPosted: Sun Apr 22, 2012 10:06 am 
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Joined: Fri Mar 23, 2012 7:58 pm
Posts: 154
Hi guys! I just finished converting my Benjamin Sheridan Classic .22 to a nitro piston kit. The 4 parts required came directly from Crosman (Gravel Agency, Quebec) Excellent service, cost effective and 2 days shipping. I used a very simple, very cheap spring compressor that just do wonder, solid and no strenght required. 15$

The NPSS parts are shorter, assembled, in lenght then the original spring parts. The installation is strait forward and very easy, you only need to dremel the back hole on the cylinder since the treading in the new guide "spring" is 1/8 inchs backward, so it's no aligned. The same goes for the tube cover. I also cleaned the inside of the cylinder and lubed everything with moly grease.

The result is very satisfying: the gun cocking force is the same but everything is smooth as silk when it fires. Less noise and recoil. Power is at least the same as the spring set-up, since I don't have a chrono I can't pull out numbers.

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PostPosted: Sun Apr 22, 2012 10:55 am 
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Joined: Fri Oct 29, 2010 12:32 pm
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Location: Ontario
Excellent, and it was not all that hard was it? Enjoy the Gas Ram...

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PostPosted: Sun Apr 22, 2012 11:00 am 
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Joined: Fri Mar 23, 2012 7:58 pm
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Once you aligned the screws (also the 2 front screws that hold the cylinder to the stock) it's as easy as a spring/piston swap :)


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PostPosted: Sun Apr 22, 2012 11:19 am 
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Joined: Fri Jan 22, 2010 1:17 pm
Posts: 1840
Location: Kingston, ON
Very good pictorial guide to the NP conversion. :drinkers:
And it is that easy...

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PostPosted: Sun Apr 22, 2012 1:25 pm 
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Joined: Sat Sep 25, 2010 7:49 pm
Posts: 1248
Location: Southern Ontario
Thanks for adding the pics. I'll really like to do the same mod to mine, but for the PAL aspect...

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PostPosted: Sun Apr 22, 2012 3:07 pm 
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Location: Komoka Ont.
They probably sell a non PAL kit.

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PostPosted: Sun Apr 22, 2012 4:46 pm 
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Joined: Fri Mar 23, 2012 7:58 pm
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Well in regard of the law you can buy any parts you want, you just can't assemble them to make a working airgun over 500fps without a valid PAL. This is why I'm not putting the technical numbers of the parts I bought in this thread. I didn't use the plastic tube cover either, you can by cutting it but my dog ate it so it will be in my next Gravel order ^^ And yes it's that easy. Thx guys for the feedback! Go on the Crosman.com website and on the manuals/diagram page, you can find any Crosman/Benjamin Sheridan part that exist and order them with a credit card. If they don't have them in stock they will order it from Crosman.


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PostPosted: Mon Apr 23, 2012 10:38 am 
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Location: Near London Ontario
I was worried putting gas rams into my springers, but low and behold, it really isn't hard. So glad it went well for you!

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PostPosted: Mon Apr 23, 2012 11:55 am 
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Thx very much! I ordered a chrono from D&L and will pull out numbers as soon as I have ^^


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PostPosted: Thu Sep 10, 2015 1:34 pm 
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Joined: Fri Sep 09, 2011 11:30 pm
Posts: 190
Location: Edmonton
Old post I know but if Sim123456 is still around,
I like to know how to get the nitro piston for the classic.

I already called Gravel but they were not able to help me.

My spring broke in 3 and I need a new one but if it was possible
to convert it to NP, i'd take that route.

Can anyone help?

thanks in advance.

Max.


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PostPosted: Thu Sep 10, 2015 1:48 pm 
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Joined: Fri Sep 23, 2005 2:29 pm
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Location: Okanagan,BC
Quote:
Last visited: Thu Oct 24, 2013 9:55 pm


:(


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PostPosted: Thu Sep 10, 2015 4:11 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1277
Location: United States
altashot: It is possible to convert it, and there are several ways to do it. Cheaper ways require more work, the more you spend on parts the easier the conversion. In the US with US $ it can be done for as little $26 +$4 shipping, but buying all the parts to make it a simple bolt together deal is more like $70. Since we can buy a complete referb nitro gun for that it's kinda pointless. I'd imagine your prices are at least double that, but I'd imagine the ratio is similar.
Dropping a nitro in may cause the gun to break the 500fps mark. There are two springs I know of that will work, the std full power and one that's ~2/3 as strong. Even the light one can exceed 500, it just depends on the other parts in the gun.


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PostPosted: Thu Sep 10, 2015 4:42 pm 
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Joined: Fri Sep 09, 2011 11:30 pm
Posts: 190
Location: Edmonton
Well I can do quite a bit of work myself, I have a machine shop at work.
What other springs can I put in there? More power would be great but I intent
on keeping it as a plinker, so it is not a must, and yes, I do have a PAL, so velocity is not restricted for me.

I would still like to convert it to Nitro though. Any idea if there's a kit?
Maybe one for another platform that'll work in the Classic?

Max.


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PostPosted: Thu Sep 10, 2015 4:52 pm 
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Joined: Sat Apr 13, 2013 12:19 pm
Posts: 369
Location: Edmonton
Sim123456 wrote:
Hi guys! I just finished converting my Benjamin Sheridan Classic .22 to a nitro piston kit. The 4 parts required came directly from Crosman (Gravel Agency, Quebec) Excellent service, cost effective and 2 days shipping. I used a very simple, very cheap spring compressor that just do wonder, solid and no strenght required. 15$

The NPSS parts are shorter, assembled, in lenght then the original spring parts. The installation is strait forward and very easy, you only need to dremel the back hole on the cylinder since the treading in the new guide "spring" is 1/8 inchs backward, so it's no aligned. The same goes for the tube cover. I also cleaned the inside of the cylinder and lubed everything with moly grease.

The result is very satisfying: the gun cocking force is the same but everything is smooth as silk when it fires. Less noise and recoil. Power is at least the same as the spring set-up, since I don't have a chrono I can't pull out numbers.

Image

Image

May I know what was the spring compressor you used and where I can get one? Am planning to do a vortek kit upgrade in my Diana 48.

Thanks.

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PostPosted: Thu Sep 10, 2015 9:14 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1277
Location: United States
altashot: You can do it with only buying the nitro and making one or so simple parts. I suppose the easiest would be to remove the spring guide tube from its base and put a metal spacer on the base that will accept the shaft end of the nitro, which you will be installing backwards. Basically just a disc of steel like a thick coin to go over the spot where the guide tube was, with a shallow hole to center the nitro shaft. Then the body of the nitro would go in the piston, which is a loose fit so you'd need something to make it snug. I'd just glue three plastic discs to the sides of the nitro at the base, but however you want to do it. However it's setup you'll want some preload on the spring because if it fully extends in use it'll pound the nitros internals and damage it. So enough that it has preload but not so much that when cocked it bottoms out. I'd probably shoot for ~4mm preload but I think you can go to ~10.
As a cheap spacer/adapter for the aft end where you removed the guide tube you could use a bolt. Like a 10 or 12mm depending on if you cut the guide off or removed it. Then cut the shaft down to 5mm long. This will fit in there and act as your spacer. Drill the hole depth in the top of the bolts head at least a couple mm deep. You may need to add washers in the piston to shim up the butt end of the nitro to get your preload. The nitro piston is 1oz heavier than a coil version which helps with heavier pellets, so adding the washers or a solid piece of steel will help add that weight if that's what you want. The weight is not a big deal so you can use aluminum if it's easier, or lead if really want weight and/or to experiment with weight. Again it all depends on what spacing is needed for preload which you not need at all depending on the bolt heads thickness and the hold you drilled.
The standard Crosman nitro body is ~151 x 18mm. The shaft is ~109 x 10. They also make a lower strength nitro that's the same size except for an 8mm shaft. Strength is ~33% less but you won't lose 33% power, more like 15-20%. It will be 33% easier to cock, smoother shooting and quieter.
Full power is # BT9M22-00-5
Low power is BT5M22-00-1
There is no kit I'm aware of, except maybe those sold to convert Gamo's, but I think those are only factory installed and much more expensive.
Things to make the conversion easier would be buying associated oem nitro parts, like the piston, end cup and maybe receiver. The end cup is # BT9M22-00-2 and cheap, but changes the way you do the install which might be more difficult. The end cup and piston makes it pretty easy. Add the receiver and it's a simple bolt together deal. But the piston and receiver are both kinda expensive.
As an option to the bolt you could use the top hat, which is the short spring guide in the piston. It's "head" is shorter and would allow for more metal/weight spacing on the piston end.


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