Shadow breech pivot screw

Shadow breech pivot screw

Joined: March 24th, 2008, 10:27 pm

November 7th, 2008, 3:39 pm #1

What is the secret to getting the pivot screw loose?
I want to tighten up the breech, but the screw will not break loose. It won't move in either direction.
I applied as much force as I could, but it does not budge.
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Joined: December 23rd, 2007, 1:28 am

November 8th, 2008, 12:40 am #2

Have reported success with an impact driver(the kind you hit with a hammer). I have not had to do it yet, but I have an impact driver for when the time comes.
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Joined: June 8th, 2008, 2:06 am

November 10th, 2008, 3:17 am #3

What is the secret to getting the pivot screw loose?
I want to tighten up the breech, but the screw will not break loose. It won't move in either direction.
I applied as much force as I could, but it does not budge.
has a rather hokey pivot bolt arrangement where the bolt screws tightly into the "far receiver fork" but only slips through a hole in the "near receiver fork". In other words, the bolt is only retained by the threaded end of the bolt and it's held with pretty strong thread locker compound.



For my Gamo440 I used a rather large screw driver with a square shank that fit the bolt slot perfectly, then I clamped a vise grip onto the screw driver shank to gain a lot of leverage. It took a LOT of carefully applied pressure but the bolt was indeed removed without damage.
Last edited by nced on November 10th, 2008, 3:18 am, edited 1 time in total.
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Joined: October 10th, 2003, 5:24 am

November 10th, 2008, 6:20 pm #4

You may be able to loosen it with a drop or two of acetone or fingernail polish remover applied to the threaded end.

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Joined: September 1st, 2005, 3:33 pm

November 11th, 2008, 6:05 am #5

has a rather hokey pivot bolt arrangement where the bolt screws tightly into the "far receiver fork" but only slips through a hole in the "near receiver fork". In other words, the bolt is only retained by the threaded end of the bolt and it's held with pretty strong thread locker compound.



For my Gamo440 I used a rather large screw driver with a square shank that fit the bolt slot perfectly, then I clamped a vise grip onto the screw driver shank to gain a lot of leverage. It took a LOT of carefully applied pressure but the bolt was indeed removed without damage.
After finally breaking the bolt on mine loose I got the feeling that the head of the bolt may be slightly tapered and locks into a tapered bore. I didn't think to grab my calipers and measure it until I'd already gotten it back together.

I ended up mushing out the slot in the screw pretty bad before it came loose, I'd sure like to know if the bolt can be replaced with a socket head shoulder bolt, that would make things a lot easier to get apart and would look a lot nicer than the beat up screw head I've got now.
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Joined: June 8th, 2008, 2:06 am

November 11th, 2008, 2:13 pm #6

fit of my Gamo 440 tonight but I thought the bolt head simply sliped through the hole in the near side fork when I removed the bolt. My main point was that the shoulder of the Gamo pivot bolt "bottoms out" on the threaded side receiver fork so there is no provision for barrel pivot tension adjustment.
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Joined: June 8th, 2008, 2:06 am

November 11th, 2008, 2:17 pm #7

You may be able to loosen it with a drop or two of acetone or fingernail polish remover applied to the threaded end.
once the bolt was loosened it screwed out normally. Perhaps heat applied to the bolt with a soldering iron would soften the thread locker but I just used a large close fitting square shanked screw driver and a Vise Grip clamped to the screw driver shank to remove the bolt.
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Joined: June 8th, 2008, 2:06 am

November 12th, 2008, 10:11 am #8

After finally breaking the bolt on mine loose I got the feeling that the head of the bolt may be slightly tapered and locks into a tapered bore. I didn't think to grab my calipers and measure it until I'd already gotten it back together.

I ended up mushing out the slot in the screw pretty bad before it came loose, I'd sure like to know if the bolt can be replaced with a socket head shoulder bolt, that would make things a lot easier to get apart and would look a lot nicer than the beat up screw head I've got now.
pivot bolt and indeed the head of the pivot bolt is tapered about .008 and fits into a tapered hole in the "near side receiver fork".

Anywhoo......after removing the barrel assembly I did find that the pivot bolt head will bind into the receiver fork ear before the threaded shoulder of the bolt bottoms out on the far fork.

Realizing this perhaps the barrel pivot geometry of the Gamo isn't as bad as I thought which makes me wonder why the accuracy is so mediocre. I've always blamed the pivot bolt geometry but I appear to be in error unless the "plastic" barrel shims used by Gamo are part of the problem.
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Joined: September 1st, 2005, 3:33 pm

November 15th, 2008, 3:49 pm #9

After fighting with the pivot bolt so long to remove it I was pretty sure it wasn't just tight threads and loctite. So the idea of using a common shoulder bolt won't work then. At some point I'll yank the screw out again and reverse engineer it. My thought is to have something like a 1/4-20 socket head cap screw turned down to have the same dimensions but with a more friendly hex head. I might make a couple with slightly shorter shoulders to squeeze the forks together a little more and if possible take out some slop.
Last edited by kornphlake on November 16th, 2008, 12:27 am, edited 1 time in total.
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Joined: June 8th, 2008, 2:06 am

November 17th, 2008, 11:48 am #10

<p><img alt="Picture008.jpg parts picture by wved" src="http://img.photobucket.com/albums/v734/ ... ></p><p>To get an adjustable pivot bolt with lock nut similar to my R9s. Notice that I used a socket head cap screw to fabricate the new pivot bolt and lock nut (see the factory pivot bolt below the home made one and the cap screw used for the bolt). I also c-bored the near side receiver fork for supporting the lock washer. I also needed to inlet the stock around the new pivot bolt head and lock nut.</p><p><img alt="Picture014.jpg picture by wved" src="http://img.photobucket.com/albums/v734/ ... "></p><p>I also turned some brass pivot washers to replace the hokey plastic ones.</p><p>Anywhoo.........all these mods to the Quest (similar geometry as my Gamo 440) did help the accuracy some (30 yard accuracy improved from about 1 1/4" ctc to 1" ctc), but not enough to justify all the effort. </p>
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