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PostPosted: Tue Jan 26, 2016 5:30 pm 
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hi colleagues,

one of my friends has received his PAL so we've recently done the mod for his Crosman Optimus .177 495 fps - the one which everybody who is 18+y.o. can buy at Canadian Tire.

Before doing so, we've tested the gun by shooting few pellets (Crosman Pointed) from ~6 ft into a piece of dry wood, then mesured the depth - it was 8...10mm. After the upgrade the same rifle did 24..28 mm (!). We've also tested it by shooting at a paper target - the accuracy is great, the recoil is uniform and no metal noise. I was afraid that the gun might went supersonic, but all the tests (10, 15, 25 yds) have shown the improved accuracy. The guy has also ordered better pellets such as JSB Exact Monster (0.670 g) which must improve the accuracy even more. I'll see the result when the pellets arrive.
Here you can see the mod/upgrade documented in pictures .

If you're interested to have the Nitro Piston mod/upgrade - please check this topic in the "Buy, Sell, Trade" for more info. I have 8x pistons more to sell and the guy who supplied them to me (he is a gunsmith also) says that those fit even more air rifles, such as Gamo 440, etc, not only Crosman Optimus, since many air guns share identical mechanical design.

Feel free to PM me for questions.

Thanks.


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PostPosted: Tue Jan 26, 2016 6:00 pm 
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PLEASE? Really!!


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PostPosted: Thu Jan 28, 2016 8:05 pm 
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What about that long piston? You gunna cut that down or replace it? Imo that's more important than the gas spring.
Or are you just here to unload the items? If so then some important questions would be; what is the brand, stroke and force of the spring? I do like that machined steel disc very much, but they can be made for free: http://airgunforum.ca/forums/topic69513 ... ilit=nitro


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PostPosted: Thu Jan 28, 2016 11:14 pm 
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Chevota wrote:
What about that long piston? You gunna cut that down or replace it? Imo that's more important than the gas spring.
Or are you just here to unload the items? If so then some important questions would be; what is the brand, stroke and force of the spring? I do like that machined steel disc very much, but they can be made for free: http://airgunforum.ca/forums/topic69513 ... ilit=nitro

Hi Chevota,

There was no need to cut anything.
The only simple and quick operation was a bit of gently hammering in order to pull the rear end terminator off the spring pipe guide assembly, please see '20160124_103344.jpg' - the 3rd image, as you can see the thing is already hammered off. There was no welding, etc.
To give you better idea how to hammer it off pls check this video https://youtu.be/Pec-5crEtb0?t=7m17s
- watch it until 7:38 -- no need to see the rest. Well, you can )) but do NOT use the adhesive tape like that guy does, because it can cause some misalignement which is not good for the gas spring and can shorten its life. Btw, my gas springs are of higher quality than the ones on that video, so no tape needed. :) The metal disk which goes together with my gas springs is working the way so the spring gets perfectly aligned itself forced by the preload. This gas spring is a perfect fit. You insert it inside the piston the thick end forward and its diameter is just perfect, it doesn't play inside the piston body. There is a little machined cavity in the center of that steel disk to match the other end of the spring.
Then look at the 4th pic "20160124_103625.jpg" -- all you need from the original assembly is the piston, the terminator and the plastic stub (the tube cover) - you see they are all placed in right order. Next you join all the mentioned parts together - see pic. 5 - similar way like it used to be. Then you will see that terminator and the plastic stub (tube cover) will be outstanding off the tube for about 1/2 inch or a bit more - it is time to put the whole tube assembly into the compress gadget - see starting form the pic '20160124_105046.jpg' pic.8 to "20160124_105235.jpg" - pic 10. Then you compress it and insert the fixed pin, install your trigger back, etc, etc
Look through the whole picture sequence once again, the Crosman diagram can be of help as well.

I can guarantee at least for Crosman Optimus .177, there is no cutting, drilling or welding involved. I did all these upgrade steps myself. The compress gadget is very easy to build too. Now it is completely new improved gun, my friend is more then happy with it.
The brand, well, I can quarantee that it is made in Russia, Izhevsk - the city of gun smiths, the fatherland of AK-47 as well as many other Russian guns :) I'm unable to measure the stroke, I don't suggest you to try to compress it anywhere outside the tube assembly.
These springs already have good history on the Russian market and well tested by many people. I receive them directly from the maker.
I can also ask to provide more information, but I don't know how does it help you.
All I know there is 82..85% of nitrogene in it, the rest is (18..15%) the dehumidified air. The internal pressure is 120atm ( =1763psi) which delivers near 1050... maximum 1100 fps when using .177 Crosman Pointed or Hollow Point pellets. This is perfect yet subsonic speed which lets you have best ratio accuracy/velocity. For the best result, the producer recommends to use 0.67gram pellets (i.e JSP Exact Heavy), some heavier pellets (i.e JSB Exact Monster 0.87 gramm) will also work very well.

Here you can see the way I receive it:
Image

the supplier can also provide the other sizes for several other brands
Image

there are also replacement piston seals made of hi-quality german polyurethane
Image
as well as the breach seals, but I didn't order those - not sure, if anybody interested then I think I could also order then supply it for ~5$ per seal.


Oh, almost forgot, there is also a nice feature - a micro valve at the thick end of the spring - it let's you drop the pressure using an allen key if you decide you need it some reason. I.e. you put both hands and the piston into the water then turn the allen key very slowly until you start seeing gas bubbles. Then if you stop and wait 2sec - it will drop approximately 20atm (15%), then you turn the key back in fast motion, etc.

p.s. If you gonna be the first customer, then I can make the gas spring price $5 less for you in hope that you test, get happy then spread a good word. :)
PM me if you're really interested.



Thanks for your interest.

_________________
.177 Crosman Optimus + Vado Performance Kit
.177 HW97k + JM Hornet Mk6 Kit


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PostPosted: Sat Jan 30, 2016 5:14 pm 
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You don't "need" to cut the piston, but you do if you want power. Cut the existing or buy a short one that is. No way in hell you will get near 1050fps using the longer piston in your pix. I can barely squeeze that kind of power from my best Crosman which is tuned and of course has the short piston. Point being you should offer a short piston as well.
The stroke of the spring is just that, how far it can compress. Put that cool little steel adapter on the end and measure the distance between it and the springs black body. The stroke of oem Crosman spring is ~109mm. Your looks about that, but if less than 100 it may not work in a gun with a short piston which is my concern. The body length is also a concern because if too long then again it won't fit a short piston.
The springs strength can be estimated by the pressure and diameter of the shaft. We have the pressure, now we just need the shaft dia... Crosman has at least two gas springs that will fit that gun perfectly, the most common is used in their advertised 1000/1200fps guns. There is also a weaker one which may be in some/many CA guns but I just don't know. Then there are two more springs that will fit that are imo too strong for the gun. By that I mean they will no doubt make more power but the drawbacks will certainly outweigh that. Maybe one day I'll try one just to see how much more power they make.
You should get the details on the other size springs this place has so people can make better decisions on what to buy, plus there are other guns people want a gas springs for. Without details on all dimensions and strength it's a gamble. As mentioned, price may be an issue too. Why buy an unknown spring from an unknown mfg when a guy can get a known spring for the same or less $.

Btw, to get the spring guide tube out I don't use any tools, I simply use the spring spacer as a slide hammer. If that doesn't make sense to anyone it will you when you have it in hand.
You should also consider offering a main seal since the oem seal is usually damaged at the factory and imo needs to be replaced. If people have to go to Gravel Agency for the seal then they might as well buy a Crosman spring there too. I hear Gravel will also sell the short piston....
I would be interested in the main seal for a std 28mm Diana which I have yet to find one better than the oem.


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PostPosted: Sat Jan 30, 2016 9:24 pm 
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Chevota wrote:
You don't "need" to cut the piston, but you do if you want power. Cut the existing or buy a short one that is. No way in hell you will get near 1050fps using the longer piston in your pix. I can barely squeeze that kind of power from my best Crosman which is tuned and of course has the short piston.

from one side you may have a point. Mechanically, lighter piston would probably also result in less recoil which is good thing. But I doubt if it would also deliver significant power increase. When gas spring extends, the pressure inside its camera drops linear, so heavier piston would probably accumulate inertia to transfer good amount of energy toward the front end. This will work better for heavier pellets, i.e. 0.67 ... 1gram. Btw, today we were shooting JSB Exact Heavy (0.67gram) and Monster (0.86gram). While there was no significant accuracy improvement for 10...15m range against Crosman Pointed (0.5gram) pellets, these JSB pellets worked much better accuracy for 25...30m targets.
From my point of view anything delivering 800..1000fps if fairly enough and works good for most of pellets. So, the speed alone must not be the ultimate goal. I.e. if you want the speed then it is not a big deal to pump more pressure into the gas spring, so there would be even no need to cut the piston - I can ask the master to make more pressure, but it would result in locking you into heavier and more expensive pellets, but the light ones would get useless because of breaking the sound barrier.

Quote:
Point being you should offer a short piston as well.

honestly, so far I don't feel like this would be good business for me. I have day work and family. Near days, maybe even tomorrow I'll put these springs (8 pcs left) on Amazon and see. If I'll have to drop the price below $45 US then I give it up. I.e. I see there is a metal repair spring which costs $50 + tax + shipping, still the gas spring is better... If it will be selling well then I'll probably also consider offering pistons, seals, etc.

Quote:
The stroke of the spring is just that, how far it can compress. Put that cool little steel adapter on the end and measure the distance between it and the springs black body. The stroke of oem Crosman spring is ~109mm. Your looks about that, but if less than 100 it may not work in a gun with a short piston which is my concern. The body length is also a concern because if too long then again it won't fit a short piston.
The springs strength can be estimated by the pressure and diameter of the shaft. We have the pressure, now we just need the shaft dia... Crosman has at least two gas springs that will fit that gun perfectly, the most common is used in their advertised 1000/1200fps guns. There is also a weaker one which may be in some/many CA guns but I just don't know. Then there are two more springs that will fit that are imo too strong for the gun. By that I mean they will no doubt make more power but the drawbacks will certainly outweigh that. Maybe one day I'll try one just to see how much more power they make.

I will ask the maker/supplier about the stroke, etc, no problem.
Imagine, the education in exUSSR is way less expensive then in North America, there is enough good engineers and mechanics who knows how to design good guns and parts. ...I.e. think of the Cricket bulpup :)

Quote:
You should get the details on the other size springs this place has so people can make better decisions on what to buy, plus there are other guns people want a gas springs for. Without details on all dimensions and strength it's a gamble. As mentioned, price may be an issue too. Why buy an unknown spring from an unknown mfg when a guy can get a known spring for the same or less $.

Good point. For the beginning I decided to order the spring for most popular and non-expensive rifle to see, if it's worth at all to get into this business

Quote:
Btw, to get the spring guide tube out I don't use any tools, I simply use the spring spacer as a slide hammer. If that doesn't make sense to anyone it will you when you have it in hand.

I like the idea. I'll give it a try. Thanks!

Quote:
You should also consider offering a main seal since the oem seal is usually damaged at the factory and imo needs to be replaced. If people have to go to Gravel Agency for the seal then they might as well buy a Crosman spring there too. I hear Gravel will also sell the short piston....
I would be interested in the main seal for a std 28mm Diana which I have yet to find one better than the oem.

I can see right now there are seals for
DIANA 31
DIANA 34
DIANA 350
DIANA 46
DIANA 460
DIANA 470
DIANA 48
DIANA 52
DIANA 54
DIANA 56

- I can try to order those if it happens to sell this batch of gas springs. I doubt if it's economical to order/sell the seals separately. How much does a seal cost for your Diana gun?

I could probably order many things for various gun models, but it takes 30...45 days to ship - but I doubt if anyone could make a deposit and wait. Let me see how it will work for the springs for some of most popular air gun models.


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PostPosted: Sun Jan 31, 2016 7:19 am 
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The point of the cut or short piston is not weight reduction, it's stroke increase. Like a Chevy 302 vs 383, the only real difference is the stoke, guess which will make more power...
Compared to the piston in the pix you should get about 25% more stroke so at bare min that same % in power gain, but in reality it will be more due to a higher compression ratio. The short piston is about the ideal weight so the long piston is actually too heavy. So a short piston is a win in every way.
Crosman used that long piston to reduce power in CA guns and it is imo the biggest factor in the power loss. The other factor is a weaker spring which I'd imagine your example gun had too but I'd bet that using that weaker oem spring with a short piston will make more power than your gas spring with the long piston.
Btw, 1000fps is 56% more power than 800, so nothing to sneeze at. It isn't so much that people will want 1000, but it does mean they have the power to use a heavier pellet which as a general rule work better. So say yours makes 800fps with the std 7.9gr, a gun that also has a short piston could shoot a better and heavier 10.5gr pellet at say 850 for a net power increase of 50%, but also a flatter trajectory and >50% power down range. It also means hollow point pellets would work much better. Yours (assuming 800 w/7.9) would be closer to 730fps using a Crow Magnum pellet, and a short piston could likely hit 920 which at target distance can be the difference between zero and excellent expansion.
So in reality a person could simply cut their piston at no cost and make as much or more power than your example gun. Plus their cocking effort will be much less and it'll probably shoot nicer too. If they choose to install a full power oem coil spring, which is cheap, then power will certainly exceed your example gun. If they choose to use an oem Crosman nitro spring it'll be cheaper than yours and they know what they're getting.
Just sayin there's no real incentive to buy your setup. So far the only thing I really like I that metal disc, but as mentioned I can duplicate it fairly easily in a few minutes using nothing but a hacksaw and drill, or just a Dremel.
So I think with detailed specs on the spring, some before and after fps #'s using various pellet weights, plus more options (piston and seal) you may have something, but as is I don't see much in sales potential.
The springs stroke and shaft dia are easy to measure yourself....

Russia may have engineers, but it doesn't mean they can actually mfg a good product. Odds are your springs were originally designed for something else, but then someone realized that if they add the deals at each end it'll work in a Crosman. No way they'd prep and mfg a new spring that will only sell a few hundred or thousand units. So my question is what strength is it, because if it wasn't specifically for this type gun then odds are it's strength is not ideal.
Now if you really wanted to sell something cool, at least what I think is cool, is a small little hand pump with a gauge to charge these springs. You said they had a screw to vent pressure, which would be extremely tricky to get right, but with a little pump the user to could adj up and down as needed. I don't mean a bicycle size pump, just a little teeny thing maybe the size and movement of a hand exerciser. The tricky part would be the valve that can be disconnected w/o losing pressure. Just a thought....

The Diana 28mm seal is the most common by far, but I'd have to see some clear close up pix of it along with some specific measurements before I'd buy it. I have several different types sitting in a drawer but they're all usless imo because they were machined incorrectly. Some are made of the wrong material to boot, too soft. Very frustrating and I'm tempted to buy some raw material and borrow a lathe to finally make a good one. If the engineers in Russia are so good then maybe they did it, but I seriously doubt it.


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PostPosted: Sun Jan 31, 2016 10:18 am 
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Chevota wrote:
The point of the cut or short piston is not weight reduction, it's stroke increase. Like a Chevy 302 vs 383, the only real difference is the stoke, guess which will make more power...
Compared to the piston in the pix you should get about 25% more stroke so at bare min that same % in power gain, but in reality it will be more due to a higher compression ratio. The short piston is about the ideal weight so the long piston is actually too heavy. So a short piston is a win in every way.


I see.
I guess that there is no point to cut the original piston, only to replace it with a new one,
since the piston locking point (where the trigger latch engages) which limits the stroke will stay same anyways?

And yeah, I will definitely do the measurements and ask the guy about the stroke.
From the other side, the tuning kit must be cheap enough to justify the upgrade, otherwise it might look more economical for people to buy another brand new air gun.

Thanks for good write up, it all makes sense.

_________________
.177 Crosman Optimus + Vado Performance Kit
.177 HW97k + JM Hornet Mk6 Kit


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PostPosted: Sun Jan 31, 2016 2:49 pm 
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Example of cut piston which someone was kind enough to share with me. This one was a nitro piston which appears rather thick walled to me, but still not too hard to cut. The overall length isn't as critical as is the aft edge of the hole for the catch. If they want absolute peak power they could make the hole a bit further fwd to get max possible stroke. The gun will only cock so far but might as well squeeze the most out of it while you're in there.
So you could drill the hole and/or use a Dremel to make it, then adjust it if needed with a Dremel or larger drill bit. Sure a new short piston would be nice but apparently rather expensive in CA. I'm guessing they're $30+CA?
The coil and nitro pistons also have a different depth inside, which makes the dimensions of your spring more critical. I'd say it's better to use/buy a coil piston for this because it's deeper inside and can be shimmed if needed. The if the nitro version is too short inside to accept your spring then you'd be screwed.
Some people I know do nitro conversions, which in the US costs ~$30 (26 spring 4 ship). Easy to do imo but most are not willing or able to do the work in that link I gave you. Buying the parts to make it a bolt together deal is too expensive, closer to $70. A complete referb Titan is, or at least used to be $72-80 so why buy all the parts when you can get a whole gun. This basically that left the option to buy just the nitro spring and do all the work, or buy a complete gun. In the end it seems most just pass on the idea.
Also there's my push for people with coil guns to simply tune the gun as-is, or if needed just buy a new oem coil spring (~$7US) instead of converting to nitro. That's assuming the gun was a full power version to begin with, which most are. Gas springs are neat but harder to cock, harder on the scope, and prone to leak. Not sure about yours but with the standard Crosman nitro springs my friends and I have seen ~ a third leak some or all pressure within a year. I've had much better luck with their other springs which use a smaller 8mm shaft that is smoother. The standard/common spring has a 10mm shaft that is rather rough so I'm surprised any of them hold. The others with smoother shafts will no doubt fail down the road, but so far they have a much better track record. So yours may have the right strength, dimensions and hold air a long time, but so far people don't have a clue about that stuff. I think you'll really need to step up your game to sell very many, and to be honest I don't think there are enough buyers to make it worth your time. Just a guess based on the few people who ask me about it, and the much fewer that are actually willing to open the gun up and do it. For many the spring compressor is the deal breaker, they both don't want to make one and they fear the process. I don't use a compressor so no problem, and some people will try that, but the majority are unwilling to even try. So that's another obstacle you have to deal with; people and spring compressors....


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PostPosted: Mon Feb 01, 2016 10:17 pm 
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I've done some research on the net regarding gas spring prices. The cheapest one I was able to find on Ebay was $37 US - no metal disk though. The rest were like 42+
So I decided to lower the price, now it is 58 CAD or 40 USD.

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.177 Crosman Optimus + Vado Performance Kit
.177 HW97k + JM Hornet Mk6 Kit


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