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PostPosted: Sat Nov 20, 2021 12:24 pm 
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Location: Ingersoll, Ontario
Does anyone know where I can get a spring plunger to do the 2 stage trigger mod to a qb78? I looked on amazon but can only find the ball style spring plungers. #2 in the picture, Thanks.


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PostPosted: Sat Nov 20, 2021 12:41 pm 
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Location: Spruce Grove AB
Is that a 4mm screw?


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PostPosted: Sat Nov 20, 2021 12:47 pm 
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Location: Ingersoll, Ontario
killercrow wrote:
Is that a 4mm screw?

From what I can find people are using a M5

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PostPosted: Sat Nov 20, 2021 12:52 pm 
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Location: Kingston, ON
I bought a whole bunch of those some time ago, and when i started back on QBs last year.. I can't find them anywhere. Anyhow, I bought them from somewhere like McMaster Carr or Graingers. I just googles and searched on e-bay I think the key words are precision pin set screw. Here is a starting point anyhow.
https://www.ebay.ca/itm/282584271689?ha ... Sw8TBZdW7d

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PostPosted: Sat Nov 20, 2021 3:50 pm 
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Location: Canada
Bought mine at Fastenal...been a few years now.

Al


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PostPosted: Sat Nov 20, 2021 4:33 pm 
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Location: Ontario
Not sure where you are, I got all the screws and plungers from Bolts Plus in Guelph ON. they ordered them in and I had them in 2 days. That was pre covid!

I sent you a PM. If you contact me I think I can help you out.

Kevin

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PostPosted: Sat Nov 20, 2021 7:18 pm 
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Location: Any Town ONTARIO
https://www.aliexpress.com/wholesale?ca ... Point+Grub

https://www.aliexpress.com/item/1005003 ... 5209%22%7D


Last edited by pelsby on Sat Nov 20, 2021 7:32 pm, edited 1 time in total.

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PostPosted: Sat Nov 20, 2021 7:26 pm 
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pelsby wrote:
https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20211120161751&SearchText=+Screw+with+Dog+Point+Grub

Those ones are solid so no good for this purpose, but you did uncover another source..I guess "spring plunger" are THE key words
https://www.aliexpress.com/item/3286475 ... 2401%22%7D

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PostPosted: Sat Nov 20, 2021 7:32 pm 
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Dukemeister wrote:
pelsby wrote:
https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20211120161751&SearchText=+Screw+with+Dog+Point+Grub

Those ones are solid so no good for this purpose, but you did uncover another source..I guess "spring plunger" are THE key words
https://www.aliexpress.com/item/3286475 ... 2401%22%7D



https://www.aliexpress.com/item/1005003 ... 5209%22%7D

are you sure it's a spring plunger it does not look like one

it looks like a dog point


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PostPosted: Sat Nov 20, 2021 8:13 pm 
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okay I read the mod site it is ball plunger I think that you need but I still believe the screw in the pic is just a dog point . This screw is replaced with a ball plunger . Maybe rsterne can clear this up ?

This is the exact screw according to Bob's pt#

https://www.kbctools.ca/products/search/1-903-52001


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PostPosted: Sat Nov 20, 2021 8:28 pm 
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Location: Canada
Spring plunger...

viewtopic.php?f=1&t=16273&hilit=trigger+plunger


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PostPosted: Sat Nov 20, 2021 8:36 pm 
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Post subject: Re: Non-PAL QB 79 on HPAPostPosted: Wed Nov 23, 2011 2:42 pm
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Location: Coalmont BC
Here are the modifications I did to the trigger.... The instructions below detail what I did.... but you can do any or all (or none) of these....

1. Polished the sear/trigger contact surfaces
2. Installed spring loaded plunger to provide a second stage
3. Replaced trigger spring with lighter one
4. Adjusted the trigger to my preferences

Note how the parts are installed and make a diagram, photo, or refer to the photo in the post above for orientation.... Start by backing off the spring adjustment screw and then pop out the trigger and spring.... Carefully lift the top half of the sear spring out of the way and remove the sear.... Polish the surfaces where the trigger and sear meet, starting with 220 grit and finishing with 600 grit.... Small pits are not important but you want the surfaces to be smooth so that they will slide over each other easily and not drag.... All edges should have any burrs removed, but do NOT change the shape or angle of anything or you may make the trigger dangerous.... The areas to be polished are circled in yellow in the photo below....

Image

I replaced the adjustment screw which was in the middle (location 2) with a small spring-loaded plunger (circled in red).... I purchased it from KBC Tools, and the part number is 1-903-52001 on page 793 in their current online catalogue.... https://www.kbctools.ca/products/search/1-903-52001


This was not my idea, I borrowed it from a CAF member from a couple of years ago (sorry I don't remember who, but thanks).... The plunger is 6-32 thread, so the hole in the trigger frame will need to be drilled 7/64" (or #36) and tapped to 6-32.... Make sure you remove all shavings from the drilling and tapping and insure there is no dirt or grit inside the trigger frame or on any moving parts.... The travel on the plunger is small, and the force to move the pin is relatively large, but because of the leverage, it provides an nice second stage providing the spring tension on the lower adjustment is not set too high.... That is why I recommend using a lighter trigger spring.... The plunger is difficult to install for two reasons.... It has a hardened drop of loctite on it to provide drag.... and there is no slot in the outside end for a screwdriver.... I scraped the loctite off with an X-acto blade and I ground a slot in the end with a Dremel cut-off wheel.... This destroys the tiny adjustment screw, but I never used it anyway.... Once you get your final adjustment, you may need a tiny drop of blue loctite to hold that adjustment (I didn't).... The numbers in the above photo indicate the stage adjustment screws and the spring tension adjusment.... The lighter spring is shown installed above.... It is 3/16" OD x 5/8" long and made from 0.020" wire, Trakar part # C0457-051-0158, but any similar spring will do as there is an adjustment screw to set the tension....

When reassembling the trigger, I used Honda Moly 60 for the pivot holes and pivot pins, the ends of the springs, and the sear/trigger contact points.... You don't need much, just a thin film will do.... Here is a photo of the reassembled trigger showing it adjusted the way I liked it....

Image

Note that the sear overlaps the trigger by about 2mm.... You adjust the upper (first stage) screw to achieve this.... Backing out the screw will provide a longer first stage travel and vice-versa.... Note that there is a small gap between the back of the trigger and the tip of the spring plunger.... As you pull the trigger, the sear overlap decreases, and the object is to have the trigger contact the second stage adjuster (the plunger) just before the sear releases.... Don't go crazy trying for a hair trigger, I set mine up for about 2/3 of the sear travel on the first stage and the last 1/3 on the second stage.... If you don't install the plunger (and therefore only have a single stage) I would reduce the sear overlap to about 1.5mm (1/16") or so.... For safety, you should not reduce the trigger spring tension too much.... Ideally, if you pull through the first stage and release the trigger with the hammer cocked, the trigger should return to the original location.... If you reduce the spring tension too far, that won't happen and the gun could fire when bumped.... not a good idea.... Replace the side plate, and you're done with the trigger mods....

More to come....

Bob

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