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PostPosted: Mon Jan 14, 2019 11:03 pm 
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Joined: Sat Nov 05, 2016 10:52 am
Posts: 2693
Location: Caronport, Saskatchewan
Nice =). I never had luck with daisy wadcutters. That looks pretty good!

Sent from my EML-L09 using Tapatalk


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PostPosted: Thu Jan 17, 2019 9:14 pm 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2647
Location: Somewheres near the Atlantic
Got the slide extender on. Ordered a 1pc mount with a rail. So I can mount a flash light to the side.

Still like to get a muzzle device, buddy was hinting.

Image

Hit the grenade solider hand..

https://youtu.be/u9brJaJ9vcQ?list=UUlDa ... vwz6OcEKHQ


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PostPosted: Mon Jan 28, 2019 2:42 pm 
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Joined: Wed Dec 05, 2012 6:52 pm
Posts: 78
The key is not piston packing but a piston resevoir ...
Heres the results of a labourious weeks work packed into a few lines here ..
I found the clearance (dead space) of the cocked piston and bulkhead wall to be just shy of 1.5mm...Adding a machined disk of 1mm i went from 385 fps JSB Exact to 407 fps.
Increasing with a new Disk of 1.4mm (virtually dead heading) i got 395 fps and lost over 10 fps?...
The opposite of what one might think, a tiny clearance is required as power dropped off ..
Figuring some clearance is required around the transfer port, i machined another disk of 1.4mm...dead heading, but with a spot face where the transfer port is of 8 mm in diameter through the disk to the piston front face...
This time i got 415 fps.....
Dont like barrel extensions, they spoil the look and pocketability of the pistol but went with one of barely 3/4 inch longer...running through the pointless void to the true muzzle...I got 15 fps...Happy with the 425 fps with reasonable weight pellet then ..


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PostPosted: Mon Jan 28, 2019 6:27 pm 
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Joined: Mon Feb 11, 2013 12:46 am
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really check this very old post....topic58676.html
extra tap mod with the RWS super H 6.9gr 427fps and after second mod 451.3fps

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PostPosted: Mon Jan 28, 2019 6:59 pm 
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Joined: Wed Dec 05, 2012 6:52 pm
Posts: 78
Yes...my work this time on a P17 but your using a very light pellet there...i would expect similar or even more ...trust me...a slight void in your front packing with will give u more ..


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PostPosted: Mon Jan 28, 2019 7:31 pm 
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Joined: Thu May 07, 2015 8:30 pm
Posts: 1162
Location: Eastern Townships, P.Q.
clarky wrote:
The key is not piston packing but a piston resevoir ...
Heres the results of a labourious weeks work packed into a few lines here ..
I found the clearance (dead space) of the cocked piston and bulkhead wall to be just shy of 1.5mm...Adding a machined disk of 1mm i went from 385 fps JSB Exact to 407 fps.
Increasing with a new Disk of 1.4mm (virtually dead heading) i got 395 fps and lost over 10 fps?...
The opposite of what one might think, a tiny clearance is required as power dropped off ..
Figuring some clearance is required around the transfer port, i machined another disk of 1.4mm...dead heading, but with a spot face where the transfer port is of 8 mm in diameter through the disk to the piston front face...
This time i got 415 fps.....
Dont like barrel extensions, they spoil the look and pocketability of the pistol but went with one of barely 3/4 inch longer...running through the pointless void to the true muzzle...I got 15 fps...Happy with the 425 fps with reasonable weight pellet then ..


Hmmm... I went from 381 to 422fps with 7 gr. RWS hobby, with only an adjustable piston, no other mods yet, with my Stoeger XP4, which is mechanically identical to the P17. Could be interesting to try a longer barrel and some other mods... 8)


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XP4_pistons.jpg
XP4_pistons.jpg [ 260.5 KiB | Viewed 214 times ]

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PostPosted: Mon Jan 28, 2019 7:36 pm 
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Location: Eastern Townships, P.Q.
Ace wrote:
really check this very old post....topic58676.html
extra tap mod with the RWS super H 6.9gr 427fps and after second mod 451.3fps


THAT is interesting :)

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PostPosted: Thu Jan 31, 2019 11:58 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1241
Location: United States
Fyi here's what I did. Cheap, easy, it helps.


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PostPosted: Fri Feb 01, 2019 7:40 am 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2647
Location: Somewheres near the Atlantic
Unfortunately now it's only shooting around 387 with 7.9s

Might need to re o ring it.


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PostPosted: Mon Feb 04, 2019 7:14 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1241
Location: United States
Did you smooth the little intake hole? And toss the orig chinese O-ring? Not that I've shot mine a lot but the O-ring still holds 5yrs after install and I'd assume it would be good for a few more. If still using the the chinese O-rings inside the valve then I'd swap those too. I also smooth the surfaces they contact in use and during install to minimize any damage or wear. Just a thought if you haven't :)


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PostPosted: Mon Feb 04, 2019 7:40 pm 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2647
Location: Somewheres near the Atlantic
Chevota wrote:
Did you smooth the little intake hole? And toss the orig chinese O-ring? Not that I've shot mine a lot but the O-ring still holds 5yrs after install and I'd assume it would be good for a few more. If still using the the chinese O-rings inside the valve then I'd swap those too. I also smooth the surfaces they contact in use and during install to minimize any damage or wear. Just a thought if you haven't :)


I never touched the piston or internals, gun been sitting on the bench for year. Till I decided to get to fitting a new barrel on another upper..


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PostPosted: Tue Feb 12, 2019 11:47 am 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2647
Location: Somewheres near the Atlantic
Today I was walking past the dollar store, so I picked up some alumfoil tape and new blades.

I Chrony the gun before and after. Was getting around 390 with 8.2grn, I shimmed the breech seal a bit with some floss. Since I don't think my barrel face is true squared ( it was turned without a lathe ) Then I added 7 layers of alum foil tape and carefully cut off the access.

Giving me around avg of 421 FPS. With the 8.2s and 412 avg with 8.6 grn. My goal was to break 400.


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