GTA
PCP - HPA - C02 Gate => QB-7X Gate -W/Co2 & HPA => : tonaka September 16, 2008, 07:11:50 AM
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... that I have are; where would one buy 9oz bottle for QB79 so that it could fit it? I heard that some are too big around to go under the barrel. My first QB 79 rifle is coming in couple of days and I am excited about it.
The second question is about tuning QB. I have read CDT tune guide and Ribbonstones tunes, mikeiniowa and I really would like to tune it on my own. I know that it would be safer to send it over to experienced person to do it but I really am the person who like to do it on my own and that way I learn a lot about the gun. BUT as you can notice ,by reading my posts, I am not native English speaker and I understand most of what I read. I have been in America for a while but some terminology or some words I have hard time to understand. So I would like to humbly ask you guys if some of you could explain in detail how to tune and power tune these guns. For example I have hard time to understand what is " PORTING the valve" is or what is a " BOLT PROBE"
I do understand a lot by reading but I am more visual guy and some pix would help me greatly.
I know some things could go wrong while tuning this gun but I still would like to do it on my own and learn from you, so please don't talk me out of it:)
Besides it can also help others members who are not native English speakers as well.
Thank you for your understanding.
AFTER ALL IT IS GREAT PLACE TO BE!!!!!!!!!!
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These are urls are for crosmans but it'll give you a good idea on what they are...
Porting a Valve:
http://www.network54.com/Realm/CFTech/Biovalveupdate.htm
To port a valve means to open up the holes a little so air/gas can escape quicker, resulting in an increase in velocity.
Bolt Probe (the probe is the tip of the bolt in front of the o-ring - it helps push and seat the pellet in):
http://www.network54.com/Forum/275684/message/1197870382/Here+are+several+++%26lt%3Bpics%26gt%3B
Extending a probe helps seat a pellet deeper so the skirt of a pellet has less of a chance of blocking the barrel port (the port on the barrel that accepts the gas from the valve).
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Thank you for the links and clarifications.
Thank you
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Yes, you can cut the stock probe off, drill a hole and insert/attach a custom longer probe. Some with access to a lathe would just make a whole new bolt with a longer probe on it.
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thank you again!! You are very fast to answer!
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Before you do anything, search around a bit more. Plus, someone may eventually chime in here as well. You'll need to know what size to open your ports up to as well as the length your bolt probe should be.
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I second what everyone else said!
Other things to take into account are tools, seals & lubricants. So far I've tuned 3 QB variant rifles. VERY Easy is you have the right tools. Namely the valve tool. I used a BIG flat bladed screw driver on the first one and scored the inside of the main tube. So, the 7/16 deep socket cut into a bi-pin spanner works REALLY well! Another nice tool to have is a Dremmel or similar rotary tool with a hard, cone shaped polishing bit and some jewelers rouge. After you open up & deburr the air passages, polish them with the felt bit and a bit of rouge. It may seem trivial, but even the slightest bit of smoothing helps flow & keeps turbulence down. Then there's the seals. You can't reuse the seals and have a reliable, leak free gun. I found this out the hard way! So it's best to order off for a seal kit from Archer Airguns or Best Airgun. The kits come with extra breach & transfer port seals and everything else needed to completely reseal your rifle.
Just take your time & pay LOTS attention to detail then you should be fine. I know how it feels when you're half way there and just want to get it done as fast as you can to see the results of your handywork. But as they say, slow & steady wins the race!
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Thank you Sam! I do have Dremel and some other tools accept for the lathe. But I think for simple tune I will be fine without the lathe.
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Going to give some hard-won advice.
Is impossible to keep the gun too clean. The grit and metal shavings created in doing a tune are DEATH TO TH VALVE....keep it clean, then clean it all again.
You can get to the 11.5 to 13 foot pound level without doing major valve mods. If that is enough for you (in .22, would be in the 600-630FPS area), can get there with the following:
1. Poly-port change (chaging the existing transfer port to one made of ice-maker tubing).
2. Smooth and polish the friction points (mostly where the hammer runs in the tube).
3. Bolt probe. Can drill/enlarge the existing bolt probe and enlarge the transfer hole if you like, it works out to be about the same.
4. Shim the main spring...not too much or it will be very hard to cock,,,just a little bit (like a 1/16" to 1/8" washer).
That should get you close to 12 foot pounds...which is a very nice balance of power and gas use.
Do understand, it's not REQUIRED. have 5 QB's, one of which is kept nearly like it came out of the box. Shoots about 600fps/11foot pounds, and has had very little down in the way of modifications....runs on 12gr. cartridges. Gets used often as it's often so much easier to just toss a few 12gr. cartridges in your pocket and go for a nice woods -walk.
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I can send you a valve tool and seals if you want some for free,.........
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Thank you for your help guys! I really appreciate it so much. By the way, do I buy ice-making tubing in any hardwear store?
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Yes you can :)
If you read around here and the crosman group there are some good ideas how to cut it square to. I like to push the back end of a tight fitting drill bit in the tube and chuck the drill with the cutting end in the chuck ( backwards of normal ) then you can turn the chuck by hand and cut with a razor knife. After a few you can get some pretty good seals. The length of the seal is important so will take a few tries.
The best idea I have seen so far was on a Canadian group. He drilled a hole in a small piece of steel and once the depth was right he pressed the tube to the bottom of the hole and pressed the blade flat to the surface to get a good seal every time. Have not tried this yet but it looks much easier than the way I have been doing it.
Have fun
Dave
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I'm not sure what size is used for a QB but I've got a whole coil of 1/4" tubing I used for my crosmans. If that's the size for the QB as well I can send you some - just let me know. I do the same thing Dave does but I secure a piece of the tubing (a little longer than needed) with the bit into the chuck. I then use a fresh exacto blade and hold it against the chuck and on the tubing as I run the drill very slowly. It has always cut a square piece for me within about 10 seconds. I then use some sand paper and sand the ends to fit snug.
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No need for you to buy any tubing....I'll be sending some already cut to fit and a chunk to play with.....
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Hay Anatoliy, when you get ready to tune your QB gimme a shout. We live in the same city. We can shoot the bull and do some test & tune! I'll bring over my 79 that I recently did up!
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you can use a smaller one , RAP4 has some also can use an Avanti, see Archers.......
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Okee Dokee Sam!!! It will be nice to meet you!
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Thank you very much Mike!! You have been such a help to me. That's amaizing!!