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 Post subject: Beeman P17 Mods
PostPosted: Tue May 19, 2020 12:45 pm 
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Posts: 192
Location: Guelph, Ontario
I bought a Beeman P17 from WesB two months ago, based on the advice of my friend YepYep and others.

I made some modifications that improved the power, accuracy and reliability of this great pistol. I thought I should share them with everyone here.

The Beeman P17 being a Chinese copy of the German HW40, had some great features. It is one of the best values in air pistols on the market. However, due to the typical problems in China with perhaps lack of attention to details, the copy is not even close to the original in terms of performance and reliability.

With these mods, hopefully, the P17 can give HW40 a good run for the money. At least my P17 after the mods, shot way better and had no reliability issues so far.

So, let's get to the mods I made:

1. First and for most, the air intake hole under the main cylinder tube. It needs to be polished with very fine grid sandpaper or steelwool. The sharp edges are known to cut into the piston o-ring leaving you with a leaking air gun unable to pump up properly.
2. The elevation adjustment screw tends to loosen with use after you pump the pistol for a few times. Some people use Locktite on the screw, some people stuff paper under the rear sight. I believe my solution works better. I replaced the metal m3 nut with a spare plastic one from my RC days. The rear sight has not moved unwantedly since.
3.Rear cocking latch pivot pin movement fix. The pivot pin tends to move to the left after some cocking. I screwed in a 3mm set screw (be careful not to overtighten, the hole is only plastic) in one of the holes running vertically on the rear of the gun. This locked the pivot pin in place. It had never moved since the mod.
4. To improve the power, I added a thin layer of aluminum tape onto the tip of the piston. This mod added about 10 fps to the pistol.
5.To lighten the trigger pull, I slightly stretched the trigger spring, also shortened It slightly by cutting off the straight end and recurve the hook to retain the original length. This reduced the trigger pull.
6. Rear sight horizontal free play. The factory rear sight had too much free play horizontally at the pivot pin. I added a small shim made from cutting a small shim and going it with Crazy glue onto the inner side of the rear sight so it takes up the free horizontal space on the rear sight.
7. Recrowning the barrel. I used brass screws and valve lapping compound. There are many videos are on the Youtube, so I won't show you how it is done.

After all these mods, my P17 can now do 3/4" group at 10m benched. Way better than 1 1/2" groups before. It is still not a HW40, but getting close, really close. At 1/5 of the price, I will take it anyday.ImageImageImageImageImageImageImageImage

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 Post subject: Re: Beeman P17 Mods
PostPosted: Tue May 19, 2020 1:00 pm 
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Location: GTA, ON
NICE~ The most surprised result is the greatly improved reliability IMO as I never heard your P17 got any problem since you started shooting it after the first tuning... Not like mine which I had to open it up and checked every or less hundreds shots until I gave up...

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 Post subject: Re: Beeman P17 Mods
PostPosted: Tue May 19, 2020 1:32 pm 
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Joined: Mon Aug 05, 2013 4:35 pm
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Location: Fredericton, NB
nice job :D

wondering about the aluminium on the piston and how that adds fps, haven't seen the piston of a P-17, i assume this seals blow by of some kind ?

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 Post subject: Re: Beeman P17 Mods
PostPosted: Tue May 19, 2020 1:58 pm 
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Location: Guelph, Ontario
Actually, the aluminum sheet take up some space to increase compression. Word of caution, There is only limited spacing between the piston head and the end of the pressure tube. Over doing it may cause damage to your gun.

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 Post subject: Re: Beeman P17 Mods
PostPosted: Tue May 19, 2020 2:00 pm 
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Location: Guelph, Ontario
YepYep wrote:
NICE~ The most surprised result is the greatly improved reliability IMO as I never heard your P17 got any problem since you started shooting it after the first tuning... Not like mine which I had to open it up and checked every or less hundreds shots until I gave up...
YepYep, you sacrificed your P17 for others not to have the same problems. I thank you for my smooth P17 ownership.

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 Post subject: Re: Beeman P17 Mods
PostPosted: Tue May 19, 2020 6:54 pm 
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Joined: Sat Mar 16, 2013 5:15 am
Posts: 3699
Location: Edmonton
Great post!


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 Post subject: Re: Beeman P17 Mods
PostPosted: Tue May 19, 2020 10:05 pm 
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Location: Guelph, Ontario
Edmonton<500 wrote:
Great post!
Thanks

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 Post subject: Re: Beeman P17 Mods
PostPosted: Wed May 20, 2020 12:35 am 
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Joined: Sat Nov 05, 2016 10:52 am
Posts: 3369
Location: Caronport, Saskatchewan
Very nice work and great layout of what you did!

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 Post subject: Re: Beeman P17 Mods
PostPosted: Wed May 20, 2020 6:56 am 
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Location: Guelph, Ontario
wesb2007 wrote:
Very nice work and great layout of what you did!

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Thank you Wes

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 Post subject: Re: Beeman P17 Mods
PostPosted: Wed May 20, 2020 3:07 pm 
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did this stuff many moons ago.... :wink:
topic58676.html

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 Post subject: Re: Beeman P17 Mods
PostPosted: Wed May 20, 2020 3:58 pm 
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Location: Guelph, Ontario
Ace wrote:
did this stuff many moons ago.... :wink:
topic58676.html
Those who tread water before me deserve all the credits. I just followed with little risk. Getting freebies felt great! Thank you Ace!

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 Post subject: Re: Beeman P17 Mods
PostPosted: Wed May 20, 2020 8:06 pm 
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not looking for credit at all just pointing it out that is has bean done before,
you did a nice job well done, there are a couple other things if you want to attempt
as i said in that thread....cheers :wink:

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 Post subject: Re: Beeman P17 Mods
PostPosted: Thu May 21, 2020 9:20 pm 
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Posts: 192
Location: Guelph, Ontario
Just added 2 more layers of aluminum tape onto the piston head (total 3, about 0.18mm). Speed with 8.44gr JSB Exact is 380 fps now. Do not recommend more layers, as is the tape already made light contact with the end of the tube.

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 Post subject: Re: Beeman P17 Mods
PostPosted: Wed May 27, 2020 2:48 pm 
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Posts: 84
The key with piston packing...FAS 6004, HW75, HW40 etc is to leave a small hole in the packing head.
If you piston pack until you smother the air intake it loses most of the gains you make by the packing in the first place.
This was arrived at after much testing by myself and a leading tuner on GTA forum
This is why your packing of 0.2mm has given you almost nothing.
You have in effect gained (or should have) about 35 fps with your 0.2 to 0.3mm packing effort here but lost 20 fps of it by smothering the air inlet hole.
What you need is a channel 3mm wide down to the stock piston face...or a 10mm hole.
This gives you your extra compression but allows efficient evacuation of this extra pressure..
However, there is only approx 35 fps to be had by such a mod in any of these models....they are what they are..
But you can do something more with the HW75

FAS 6004 with smallest cylinder but longest barrel can be modded to 400 fps with 0.4mm of packing.
(It is under too low compression stock at 330 fps and can have the biggest gain from this mod)
HW40/P17 with biggest cylinder but shortest barrel can take 0.2mm for 400 fps.
HW75 medium size cylinder and barrel can take 0.3mm for 400 fps
HW75 can be modded further if interested to 440 fps.
All JSB 8.4


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 Post subject: Re: Beeman P17 Mods
PostPosted: Thu May 28, 2020 2:13 am 
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Joined: Sun Jul 01, 2018 10:37 pm
Posts: 192
Location: Guelph, Ontario
clarky wrote:
The key with piston packing...FAS 6004, HW75, HW40 etc is to leave a small hole in the packing head.
If you piston pack until you smother the air intake it loses most of the gains you make by the packing in the first place.
This was arrived at after much testing by myself and a leading tuner on GTA forum
This is why your packing of 0.2mm has given you almost nothing.
You have in effect gained (or should have) about 35 fps with your 0.2 to 0.3mm packing effort here but lost 20 fps of it by smothering the air inlet hole.
What you need is a channel 3mm wide down to the stock piston face...or a 10mm hole.
This gives you your extra compression but allows efficient evacuation of this extra pressure..
However, there is only approx 35 fps to be had by such a mod in any of these models....they are what they are..
But you can do something more with the HW75

FAS 6004 with smallest cylinder but longest barrel can be modded to 400 fps with 0.4mm of packing.
(It is under too low compression stock at 330 fps and can have the biggest gain from this mod)
HW40/P17 with biggest cylinder but shortest barrel can take 0.2mm for 400 fps.
HW75 medium size cylinder and barrel can take 0.3mm for 400 fps
HW75 can be modded further if interested to 440 fps.
All JSB 8.4
Thanks, I will give it a try! [emoji12]

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