QB78 Deluxe trigger group question
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QB78 Deluxe trigger group question
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Topic: QB78 Deluxe trigger group question (Read 1910 times))
RickOlson
Shooter
Posts: 12
yes
Real Name: Rick
QB78 Deluxe trigger group question
«
on:
July 21, 2016, 11:06:30 PM »
Hey Everyone,
I purchased a QB78 Deluxe a few months back and just started shooting it straight out of the box. I've put about 150 pellets through it just to get to know how it shoots. So far I'm very happy with it, and after searching around the internet and this forum I've decided to strip it down, open up the valve, polish and lube it, etc. including replacing the breach seal, and the bolt.
When I disassembled the trigger assembly to clean, de-burr, and polish the components, I noticed that the sear is wobbly on the pin and sits canted off to one side. When I released the spring I noticed it seems very loose on the pin. Is this something to be concerned about or not? I have been very pleasantly surprised at how nice the trigger seemed while shooting it, but seeing how loosely that fits I'm wondering if it would be even better if it sat squarely on the pin and contacted the trigger evenly.
I've thought about getting a piece of small brass tube to go over the pin, and drill out the sear to fit on the brass to create a bushing.
Am I wasting time with this little issue, or am I on the right track? Has anybody else noticed this with their guns, and if so, how did you fix it?
Thanks,
Rick Olson
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Hastings, MI
nervoustrigger
GTA Senior Contributor
Posts: 8701
The Grin Reaper
Real Name: Jason
Re: QB78 Deluxe trigger group question
«
Reply #1 on:
July 22, 2016, 12:59:55 AM »
Both the sear and trigger blade have always been a very precise slip fit on QB triggers that I've worked on.
I would be tempted to do just what you described to bring the contact surfaces into parallel with each other.
They can be very nice triggers when polished and adjusted properly. The way you write and convey your thoughts, I bet you would have a successful and rewarding result.
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MS
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RickOlson
Shooter
Posts: 12
yes
Real Name: Rick
Re: QB78 Deluxe trigger group question
«
Reply #2 on:
July 22, 2016, 06:48:22 PM »
Thanks Jason for the reply and kind words. I'm thinking I will look for for the brass tube to make the bushing at the local hardware store over the weekend. I have access to some very fine drill bits to drill out the sear to match the O.D. of the brass tube.
If I remember to photograph this before I get started I will post some pics later.
Thanks,
Rick
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Hastings, MI
Genolution
Shooter
Posts: 57
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Real Name: Chris
Re: QB78 Deluxe trigger group question
«
Reply #3 on:
July 23, 2016, 03:57:29 AM »
I had a similar idea to fix a clock. This is what I used
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Battle Creek, MI
RickOlson
Shooter
Posts: 12
yes
Real Name: Rick
Re: QB78 Deluxe trigger group question
«
Reply #4 on:
July 23, 2016, 11:19:30 PM »
Thanks Chris,
That's exactly what I was looking for. I found a piece of 5/32" x 12" tube at Ace in Hastings for $1.49. The same piece from Amazon was $13.90.
I brought it home, but had to work today. Hopefully I will get it finished tomorrow. I tried it on the 1/8" pin in the trigger, and it slides on the pin easily but not as sloppily as the current sear flops around on it. 0.156" (5/32" OD) - 0.028" (0.014" wall thickness x2) =0.128" ID to slide nicely over the 0.125" pin. Should be perfect with a little lube in there.
I'm planning to drill the sear just a little on the small side, then put my brass tube bushing in liquid nitrogen and then press it in. Should be about perfect. My son works in a shop where they manufacture vacuum pumps and use that process all of the time to press very tight parts together. Freeze the internal one with liquid Nitrogen and press it in. Works every time if the machining is done right and within the tolerances required.
Rick
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Hastings, MI
nervoustrigger
GTA Senior Contributor
Posts: 8701
The Grin Reaper
Real Name: Jason
Re: QB78 Deluxe trigger group question
«
Reply #5 on:
July 24, 2016, 09:46:17 AM »
Interesting thought regarding the liquid nitrogen to achieve a press fit. Sounds like a real challenge considering both the tube's small dimensions and its minuscule thermal mass. I would recommend just a slip fit and a little threadlocker.
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MS
Conduct yourself so that when a man accuses you of something dishonorable, no one will believe him.
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RickOlson
Shooter
Posts: 12
yes
Real Name: Rick
Re: QB78 Deluxe trigger group question
«
Reply #6 on:
July 24, 2016, 08:22:24 PM »
Jason,
Thanks for your idea. I haven't had time to do anything with it yet. Busy weekend with work, and wife getting ready to visit her daughters for a week.
Now that she's gone I will have some time to kill and need projects to keep my mind off missing her. She's a gem. Already looking forward to her return. :-)
I've not done the liquid nitrogen process before, but my son uses it daily at work in his machine shop. I have access to it through my work on the dairy farm so I thought I would give it a try. If it doesn't work I can always drill it out for a slip fit with the threadlocker as you suggested. I have that on hand too.
Thanks again for your input. I will let you all know how it turns out in a day or two.
Rick
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Hastings, MI
RickOlson
Shooter
Posts: 12
yes
Real Name: Rick
Re: QB78 Deluxe trigger group question
«
Reply #7 on:
July 30, 2016, 10:47:51 PM »
Well it took longer than I hoped, and way more complicated than I originally thought, but it's done, and I'm very happy with the results!
Very long story short, I ended up using a 3/16" nylon bushing that slid on the sear pin smoothly. Drilled out the sear to 3/16". Cut a piece of the nylon to the same length as the thickness of the sear and pressed it in the hole. That was a very tight fit, and caused the ID to be reduced. So I took a very small diamond bit on my Dremel and worked it very slowly until the sear slid smoothly onto the pin again. Lubed it with Lithium grease and it's a beautiful thing.
While I had it apart, I polished up the rough edges the sear and the trigger. Shoots smooth as silk now. Also lightened the spring tension on the trigger a little too. I had liked it before, I love it now.
Since I went this far I decided to do several other mods while it was apart. I ordered an XP Tune Kit from AAG. De-burred and polished the breech. Polished the new bolt also. Very smooth cycling of the bolt now. Was pretty stiff and catchy before.
Totally modded the valve. Milled some slots down two sides of the body, tapered the brass head on the valve, and reduced the diameter of the head on the piercing pin to match. Opened up the throat in the brass valve head. De-burred the set screw opening and opening from the breech seal inside the breech, and polished them with 600 grit paper. Very carefully drilled out the port into the barrel. When I put the barrel inside the breech to check if it was a smooth fit yet I happened to notice the hole in the barrel behind the pellet was very small compared to the hole in the breech. I thought it makes no sense to open up every other part of the valve, porting, larger breech seal and the new XP bolt and choke it down where it finally almost gets behind the pellet. So I very carefully drilled out the CO2 port into the barrel and de-burred and polished that as well to match the diameter of the port on the breech side.
I took it out and shot it this evening. WOW! It has a much louder crack than before. I do not have a Chrony yet so I can't give specifics on fps, but I'm thrilled with the performance. Only problem I have, which was a problem before I started this is that I have no more downward adjustment on the rear sight and at 15 yards it now shoots 3" high. Previously it shot 2" high. I got the poi figured out and in a few minutes I shot a 5 shot group with 3 of the pellets making a jagged hole on the lower left side in the bullseye. The other two were slightly above the bullseye. I was tickled.
The obvious solution is to put a scope on it, but the reason I purchased this gun was to shoot pigeons and starlings in our dairy barns. Most of the time it is low light conditions in there and it's difficult to quickly acquire the target and get a shot before they fly away. With these Tru-Glo open sights I popped about 14 pigeons and ten starlings very quickly when I first purchased this gun.
Since I can't lower the rear sight any more, my other option as I see it is to raise the front sight somehow. Anybody have any ideas on how to accomplish that?
I'm all ears.
Thanks.
P.S. I do have some pics of the trigger and sear issues, but I need to log in from my phone to load them. I don't have a way to download them from my phone to my computer.
Rick
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Hastings, MI
nervoustrigger
GTA Senior Contributor
Posts: 8701
The Grin Reaper
Real Name: Jason
Re: QB78 Deluxe trigger group question
«
Reply #8 on:
July 31, 2016, 10:12:51 AM »
Nice job! It sounds like you went all out. Smoothing things out will make it much more enjoyable to operate.
Opening up the passages will have made it shoot harder but be advised it will waste CO2 big time unless you do something to reduce hammer strike. The anemic passages of the stock parts make that less of a problem.
What you can do is clip the hammer spring one coil at a time until the velocity just begins to fall. Or you can make a rear velocity adjuster and dial it in. That will also make the bolt work as a cock-on-open which I prefer anyway.
Regarding running out of adjustment on the open sights, a few options are to shim the front sight, or epoxy a small piece of material to the blade, or file off the blade and drill to accept a post (segment of drill bit shank).
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MS
Conduct yourself so that when a man accuses you of something dishonorable, no one will believe him.
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Gipper
Sharp Shooter
Posts: 519
Real Name: Brian
Re: QB78 Deluxe trigger group question
«
Reply #9 on:
July 31, 2016, 10:38:31 AM »
It seems odd for the rifle to be so far of to me, so lets check the obvious....did you clean the barrel?....how does the crown look?...a small buu may be affecting POI. ...does it load smoothly? ...something in the lead could be nicking up the pelltes....Is the barrel bent?
Just a few simple things to look at before you start modifying.
Brian
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Belleville, IL.
Curernt airgun fetish..Low serial numer RAW HM1000 - .22
RickOlson
Shooter
Posts: 12
yes
Real Name: Rick
Re: QB78 Deluxe trigger group question
«
Reply #10 on:
August 01, 2016, 12:04:11 AM »
Hey Guys,
Regarding the CO2 usage, from what I've read 35-40 shots is what I should expect from this gun after the mods that were completed, and at 40 shots last night at about an even 70 degrees I finally noticed a drop in the poi, so I'm not sure I see any reason to add a power adjuster yet.
I'm wondering if I put a TKO or similar silencer on it, and remount the front sight to that if I might gain the adjustment I want for the rear sight, and dial it right in to bullseye. Would be like adding a shim I think.
Gipper, I have checked the items you suggested other than I have not cleaned the barrel. Everything checks out smooth. The gun is very consistent in its poi if I don't pull it. But it has shot high ever since I opened the box. But I have to say that I expected it to shoot even higher/ flatter with the increased velocity from the mods and it did that.
The crown is smooth, the pellets load easily and I don't see anything else that is obvious. The sights are very well aligned as the pellets are vertically consistent. If I shoot from a rest there is almost no side to side movement. Just shoots 3-3.5" high at 15-20 yards.
I have not practiced with it at longer ranges yet, but it might be right on the money at 30, 40, or 50 yards, but most of my shooting with this gun will be in the barn from 10-20 yards maximum.
Thanks for helping me think this through and sort this out guys.
Have a great night.
Rick
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Hastings, MI
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QB78 Deluxe trigger group question