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PostPosted: Fri Apr 21, 2017 10:22 pm 
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Joined: Thu May 07, 2015 8:30 pm
Posts: 1184
Location: Eastern Townships
Anyone ever tried it? I saw on the net that some peoples use this setup with good results, and Vortec manufacture replacement kits for some models of air rifles: http://vortekproducts.com/ourstore/Airg ... ing%20Seal

It seems to give better consistency from shot-to-shot, especially in colder temp., and give a slight boost in fps (maybe 5%?) due to lower friction.


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PostPosted: Fri Apr 21, 2017 10:49 pm 
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Joined: Wed Jul 01, 2015 2:14 pm
Posts: 305
Location: Manitoba
Tried one, worked ok except for it having no material in front of the seal to cushion the piston during shot cycle so I had a metal to metal contact when I took a shot. I went back to a parachute style seal that has more seal material in front to cushion the piston during shot cycle.


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PostPosted: Sat Apr 22, 2017 6:36 am 
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Location: Eastern Townships
robertr wrote:
Tried one, worked ok except for it having no material in front of the seal to cushion the piston during shot cycle so I had a metal to metal contact when I took a shot. I went back to a parachute style seal that has more seal material in front to cushion the piston during shot cycle.


Good to know! I may stick with a commonly available seal then.


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PostPosted: Sat Apr 22, 2017 9:32 am 
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Joined: Thu Oct 04, 2012 10:27 am
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Location: Thunder Bay,On.
Superb seals......try using heavier pellets to eliminate or reduce piston slam.…not TOO heavy of course because you may invite piston bounce instead....but this is the same for stock seals also.....Way too light or way too heavy is bad☺

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PostPosted: Sun Apr 23, 2017 6:41 am 
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Joined: Thu Feb 02, 2006 11:35 pm
Posts: 3099
Location: Alberta Canada
BSA was one of the founders to use oring upon their piston versus the general parachute seal back in the late 60's early 70's.
It all plays a part upon clearances that the oring and cylinder have together. The use if an oring does open up a couple cc's of cylinder volume which translates into more air being at the pellet. And yes you do require some form of bounce absorbsion from the piston. That could be nothing more then an oring in behind the oring button head or that of an oring slot machined into the face of the button head for that piston slap at the end of the cylinder. People have even experimented with piston rings from small engines ie chainsaws. But without something to absorb the piston slap the result is it does create a very harsh firing cycle upon a piston airgun.

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PostPosted: Sun Apr 23, 2017 8:05 pm 
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Location: Eastern Townships
Thanks for the info, MyCrosman!

Whitewolf, you just gave me the parameters I needed for a prototype, thanks for that :)

I understand I'll have to carefully de-burr, hone and polish the tube, and size it precisely, and make a piston head accordingly. I'm guessing 0.003'' of clearance should be good. I can use the dial bore gauges and mics where I work, that will help.

Just not sure yet about the o-ring material, and lube to use :?:


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PostPosted: Sat Apr 29, 2017 6:59 pm 
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Location: Eastern Townships
Yesterday I bought some virgin teflon round stock and nitrile o-rings in 018 size, and today I made a first piston head prototype. I was amazed at how easy teflon is to machine. Sharp tool bits help a lot but it's nonetheless easy to cut a clean finish :)

ID of the spring tube is 0.991'' once de-burred, honed and mirror polished. The piston head is 0.981'' in diam. for the rear portion and 0.963 in front, and 0.275'' thick (about the same as the stock seal). The o-ring is compressed 0.004'' on its section. I'll soon put the parts back together and be able to do a first test. 8)


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PostPosted: Sat Apr 29, 2017 7:24 pm 
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Joined: Sun Apr 23, 2017 4:10 am
Posts: 61
Not sure this piston head will last for long.

BTW, original piston seals for Mp-60/61 (and all other baikal springers, the seal are the same for all models) are very inexpensive. At least in Russia :roll: :rolleyes:

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Rifles: Horhe Jager .22 (LW barrel, 4500psi tube), Mp-512, Mp-60
Pistols: 46M, Zoraki HP-01 ultra, 2240, baikal drozd.


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PostPosted: Sun May 14, 2017 6:18 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1271
Location: United States
I think the O-ring setup is cool but, only if it actually seals. The pressure almost certainly exceeds 1kpsi so who's to say it's actually sealing when it counts? Imo the only way to verify is with a crony. Anyone who knows me knows I like to eliminate dead air space at the seal end which involves sanding the seal down so it's dangerously close to allowing the dovetail to hit breech block. That particular Vorkek O-ring seal (28mm) is a pretty good fit on a Diana and should never hit, but in chinese or whatever mfg 28mm gun who knows.
As robertr mentioned his hit did, which can be devastating to the gun and scope. If the clearance is good and you don't have leakage then it's no doubt leakage. If the dove is too high then it needs a shim under the seal, which may not be possible, or sand the dove down until it is clear. If clearance is good then either the breech or O-ring is leaking, maybe both.
In order for the O-ring to hold that kind of pressure it'll need to be a tight fit, and a tight fit will cost some power via friction. A parachute seal only gets tighter as needed, and the material and especially the cut of the groove will determine if the seal is sealing too little (unlikely) or sealing too hard (almost certainly). To hard wastes power but that's another can of worms, but the point is the O-ring has to seal with 100% force the whole time so it's too hard 95% of the time. The receiver could be made or modded to avoid this but too much work. Many receiver tubes are tighter at the aft end so it may seem like a good fit, but where it counts it could be too loose and leak. So the O-ring it needs may seem way too tight and people probably won't use it.
Parachute seals design from a performance standpoint can vary drastically, so one may be outstanding while another is killing performance. Eg; the oem Trail XL seal sux, as does the Vortek 28mm Diana parachute seals I've seen, reason being they have too much dead space in the groove. Not the end of the world, just totally unsat for me and a waste of performance that can be avoided.
To check an O-ring I'd simply eyeball it and feel it's fit, then verify it makes full power compared to the parachute. I'd make extra effort to minimize friction by sanding the receiver tube with say 320, then 600 so it'll hold lube yet be very smooth, then I'd dry lube the O-ring and the tube, then a coat of thin grease so friction will be minimal. I do this for parachute seals too, but it would be more important for O-rings since they're tight all the way down. If prepped and lubed well enough the friction should have very little effect on power. If there was any concern it might be leaking I'd try one size up O-ring and crony it. If it gained power then it was leaking and I might try one more size to verify.
I think the orig O-ring or one size up will cover most guns, but guns and even O-rings vary so who knows. This is no doubt why mfg's like parachute b/c it only has to be close and it'll work, so sloppy mfg tolerances don't matter.
Btw the seal they sell for the Air Arms 200 will fit a std Crosman B18 if anyone wants to try, but it's pretty hard to beat the oem Crosman B18 seal, specifically if it's been sanded to fit.
Something else to think about is dry firing b/c the O-ring seal will be harsher on the gun and especially the scope if dry fired.
Another thing is I won't use silicone in my springers and O-rings are more sensitive to motor oil than the oem seal. Just something to keep in mind, so if an O-ring is used I'd only use top quality, preferably Viton, and I'd be aware it has a lifespan. I suppose you could use pellgun oil instead which is easier on rubber, but they still have a shorter life than a typical parachute seal. Not a big deal to swap out, but remember they shouldn't be stored either, only bought fresh when needed b/c they do degrade on the shelf.


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