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PostPosted: Sat Mar 27, 2021 10:52 pm 
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Joined: Thu Oct 13, 2005 4:20 pm
Posts: 1843
Location: Spruce Grove AB
Hey I figured out how to upload pictures! :lol:

Anyway here's the second piston finished and ready for installation.

Had to use the rod from the first build, my lighter rod idea was too much hassle and didn't do what I wanted.

So now, working with a 261 gram piston, with 0.35" longer stroke than the 330 gram one i built earlier.


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PostPosted: Sat Mar 27, 2021 10:53 pm 
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Location: Spruce Grove AB
...


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PostPosted: Sun Mar 28, 2021 1:23 am 
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Joined: Thu Oct 13, 2005 4:20 pm
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Location: Spruce Grove AB
Ended up at 20 ft/lbs, or 600 fps with the jsb.
A lot tamer to shoot than the heavy piston. Going to add a 23g brass spacer to the piston, also adding .45" to preload so the spring will be near coil bind...


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PostPosted: Sun Mar 28, 2021 9:28 am 
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Joined: Tue Jun 03, 2008 5:46 pm
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Location: Canada
Looking good! I like the new "pictures included" thing too. :wink:

Al


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PostPosted: Sun Mar 28, 2021 12:55 pm 
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Location: Kingston, ON
killercrow wrote:
Ended up at 20 ft/lbs, or 600 fps with the jsb.
A lot tamer to shoot than the heavy piston. Going to add a 23g brass spacer to the piston, also adding .45" to preload so the spring will be near coil bind...

Awesome machining going on there, it's bound to be a sweet shooter.
It's awesome you could achieve 20 ft lb and tame this magnum. I wonder if there is a market for your custom tune piston? Hmmmmm.
:drinkers:

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PostPosted: Sun Mar 28, 2021 1:19 pm 
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Location: Spruce Grove AB
Yeah pictures help! I'm sure following a link to see them isn't very popular. Had to download a file compressing app... It works.

I guess I'm at a crossroads now... do I sacrifice velocity for shootability? At 24 ft lbs it was a total beast... Borderline unshootable. my guess would be that it needed heavier pellets to be more efficient.

I put that brass slug in the piston Last night and I reached coil bind... Measurements were off somewhere. So I gave up and went to bed :lol:

I would be ok with finding a market for these pistons. Curious to see how many people would actually be interested.


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PostPosted: Sun Mar 28, 2021 1:24 pm 
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Location: Kingston, ON
killercrow wrote:

I would be ok with finding a market for these pistons. Curious to see how many people would actually be interested.

Well, almost everyone that has a xs28 or D350 (or similar) complain they eat scopes and are a bitch to group. So if you could sell a tune kit that kept the power up and tamed the shot cycle, I imagine there would be a world wide market for such a thing - but I'm not a businessman so don't quit your day job. :drinkers:

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PostPosted: Sun Mar 28, 2021 3:08 pm 
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Location: Spruce Grove AB
There's Mike melick in the states, he sells tuned versions of this gun. Everyone loves it. Wonder what the legalities of that would be. Buy bulk, set them up and flip them. :idea:


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PostPosted: Sun Mar 28, 2021 7:06 pm 
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Location: Alvinston, Ontario
I would consider one for my Diana 350.

Sent from my LG-H873 using Tapatalk


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PostPosted: Mon Mar 29, 2021 7:27 am 
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Location: Spruce Grove AB
cwild1971 wrote:
I would consider one for my Diana 350.

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Well you know... I think it would be logical to have someone who does a lot of shooting, take one of these kits and test it out. Then give feedback. :wink:


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PostPosted: Thu Apr 01, 2021 4:54 pm 
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Location: Spruce Grove AB
Well, I haven't given up yet. Just been busy with work and life stuff... But my fancy delrin piston head with the steel nipple worked fine until I messed with the seal tolerance, or I guess call it the chamfer that the seal is held against. (Does it have a name?) I marred it taking it apart so I touched it up on the lathe and that caused the seal to lose its seal :lol:
I took 3 shots.
1- 600 fps
2-540 fps
3- 400 fps

Redesigned piston head is in progress. Using aluminum. Nothing too fancy but I want to keep it light.

I have actually been doing a lot of research on the Google, found an old thread by a guy who started making rotating and skirtless pistons, reducing compression chamber diameters, changing stroke lengths. Good read. https://www.airgunforum.co.uk/community ... 071/page-7

Looks like I'm going in that direction. I remember seeing a picture of a skirtless piston, realized it would only work in a side or under lever... Or wouldn't it? I don't think it would be too difficult to put a sliding compression chamber into a break barrel. Might try it one day.

Anyway, long weekend, got time to play :lol:


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PostPosted: Thu Apr 01, 2021 9:10 pm 
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Joined: Mon Mar 28, 2016 1:32 pm
Posts: 160
Location: Edmonton
Nuts. Do you have a spare seal? I've got a spare 28mm Aussie seal, the moly impregnated one. Although... I did mess it up a bit. Saw a video online where you install the seal by placing it flat on a table and pushing the piston down into it in a twisting motion. Well.... turns out the Oz seal is softer than the factory seal and I perforated mine a bit. Zoom in and you'll see it. Found the best way to install the Oz seal was to get a portion on the dovetail first and using a small screwdriver, stretch it out over the dovetail until it falls in. It's yours if you want it. Even with the perforation, the dovetail should hold it fine on cocking back and the perforation shouldn't matter when the piston's launched forward.

Hah! You just discovered Tony Leach's work. Bigtoe is Tony. Yeah his very light, skirtless pistons are fantastic. Got it on my TX. It's almost practically just a seal on a tophat with bearings (see 2nd pic here: topic81159.html ) just a heads up if you want to go there.. the biggest issue with smaller diameter pistons is the heat. The generated heat will eat up thin-lipped seals like nothing. 22mm is definitely optimized for sub12fpe.

Anyway, let me know if you want the seal. Might even have a Diana seal here somewhere. Just have to find it.


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PostPosted: Fri Apr 02, 2021 12:14 am 
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Joined: Mon Mar 28, 2016 1:32 pm
Posts: 160
Location: Edmonton
NVM, I think I misunderstood. You modified the dovetail on the piston head altering the fit of the seal. The seal itself is fine.


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PostPosted: Fri Apr 02, 2021 12:15 am 
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Location: Spruce Grove AB
Yeah Tony leach! He came up with some pretty cool ideas, and very thorough testing. It's been a pretty exciting discovery for me, I had no idea the actual extent guys go to with tuning springers.
Like a whole nother animal. :lol:

I don't remember where i discovered it, but someone posted a technique for seating seals on dovetails. He uses a small 1/4" drive socket slightly larger in outer diameter than the dovetail, lightly lube the seal and slip it over the socket, butt the socket up to the dovetail with the seal near the end then put in a vise, or clamp, I just brace it with my hip against the work bench. Slip the seal on. It pops right on. Wish I had known that years ago!

I get the power levels they were working with are pretty low with the smaller chambers and all. All the reading I've been doing, I really want a hw77 now. Been eyeing them up for years. Bought a hw80 Instead a few years back and ended up hating it. I also wasn't set up for tinkering at the time either. Was all caught up with gun powder burning.

Spare seal? Hmmm.


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PostPosted: Fri Apr 02, 2021 12:16 am 
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Joined: Thu Oct 13, 2005 4:20 pm
Posts: 1843
Location: Spruce Grove AB
Ah just saw your last post.
Yes you are correct.


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