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PostPosted: Sun May 12, 2019 11:13 am 
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Joined: Fri Nov 23, 2007 3:51 pm
Posts: 37
Location: Montreal
Hi. on my new Beeman QB78 synthetic, the trigger is only fair.... I am wondering if I can polish the sear ?( hopefully I have the right name...I mean the 2 parts touching and preventing firing,, the parts showing through the small viewing window(hole) ) have you ever done it ? one question...I read somewhere some trigger and make of compressed powder steel and should not be played with.... also I would like to know: can I expect parts to fly all over the place if I remove the 2 screws and open it ? what can be done to make it better please ? do you have pictures of your work ? thanks for your help.

Image

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stef


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PostPosted: Sun May 12, 2019 11:31 am 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8972
Location: Coalmont BC
Yep, you can polish the trigger and sear.... The yellow circled areas are what needs the work....

Image

Don't change the angles, start with 220 until you remove any machining marks or pits.... then progress to 400, 600, even 800 if you have it.... I also replaced the overtravel screw with a spring plunger "2" and used a lighter trigger spring "S"....

Image

Screw "1" adjusts the amount of sear engagement (large circle in the second photo)…. Don't make that too small, or the trigger will be unsafe.... The gap between the spring plunger and the back of the trigger give you a "1st stage", where only the trigger spring is loaded against your pull.... Once the trigger contacts the pin in the spring plunger, you have the added force of that to give you a "2nd stage"....

You can polish the surfaces without adding the spring plunger, of course.... and also adjust the tension on the trigger spring.... There is a screw on the back of the trigger for that, under the letter "S"....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun May 12, 2019 2:08 pm 
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Joined: Fri Nov 23, 2007 3:51 pm
Posts: 37
Location: Montreal
Thank you so much for your help Bob.

what king of trigger weight do you get with the mod you did ? I'm looking for a 1.5 to 2 pound crisp trigger ?

have you ever tried to cut the trigger spring instead of replacing it with a weaker one . Is cutting a common practice with this trigger

thank you

stef.


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PostPosted: Sun May 12, 2019 3:21 pm 
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Joined: Fri Jan 22, 2010 1:17 pm
Posts: 1812
Location: Kingston, ON
I have always used lighter springs rather than cutting the stock spring.

Some useful links:
https://www.youtube.com/watch?v=lWICuLBHYvA
https://www.youtube.com/watch?v=1hF9sLAHb2U

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PostPosted: Sun May 12, 2019 4:29 pm 
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Joined: Fri Nov 23, 2007 3:51 pm
Posts: 37
Location: Montreal
job done ! :D

the worst was the rust on the 3 shafts rotating the parts...
those guns are assembled in a flash and they don't put oil where it's needed.....

now it's all polished, oiled and a bit of grease where it's needed.

for now I like the pull on the trigger. maybe in the future I will change the spring...

Anyways thank you for having given me the courage to do it. Thank you for sharing your knowledge.

happy shooting.
stef.


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PostPosted: Sun May 12, 2019 5:56 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8972
Location: Coalmont BC
Cutting a spring reduces the preload (but that is adjustable anyway), but it increases the spring rate.... That means if you set it to minimum preload the trigger will get harder to pull the more it moves.... A lighter spring does the opposite the increase in force required as the trigger moves increases less.... You can start with more preload and end up with a lighter pull at the release point.... Best to use a lighter spring and more preload....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun May 12, 2019 6:20 pm 
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Joined: Fri Nov 23, 2007 3:51 pm
Posts: 37
Location: Montreal
I understand. thank you
Stef.


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