GTA
PCP - HPA - C02 Gate => QB-7X Gate -W/Co2 & HPA => : Wallis June 15, 2006, 03:59:03 PM
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Hey guys,
I am in the process of changing a qb78 in 22 to 20 caliber. So far everything is going good. I did some valve work on the gun. Right now Im waiting on my barrel blank to come in, I have order a walther match barrel 19 3/4 in length. if anyone has done this before me. what should I change/ check out. Once the barrel comes in I will start the milling process of the breech. Hopefully this will work out fine for me. if not it's only money :p
BTW great looking site.
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If you plan on making a new bolt let me know, I have some 1/2 inch stainless steel that is soft enough to machine. I'll be glad to send you a chunk to use.
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I will let you know about the spare piece of stainless .
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Getting closer to doing my conversion. So far the barrel is in route to me as we speak. The valve is all ready to go, so is a scope I'm planing to use. I had to order another chrony, mine died. A mixture of water and live voltage going to the unit. Once i get everything together, I will post some pics of the progress. TTYL
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A Mike Melick tuned 177cal. But he spoiled me with the 22cal I also bought from him. So I got me a 22cal barrel for it and done some machine work on the bolt and some on the barrel. Now Im good to go. I have two QB 78 22cal that I just love to shoot. Good luck on you project.
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got my barrel in today. I'm having a hard time figuring out which end is the muzzle. The barrel is choked, both ends are tight. Any ideas on finding out how. I tried the pellet test both ends area tight fit.
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I have a Walther barrel blank and the end with the saw marks isn't the muzzle, check yours and see if it could be that easy. I am sending the bolt in the AM. Thanks, Mike
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Thanks mike, I e-mail the gentleman that I got the barrel from, right after I posted on here. He told it's the end the is flat.
Thank you for the bolt, I sure hope this conversion works like I want it to. If not I can always try again, at least I will have a spare 177 bolt if I ever need one.
One other thing I have a new chrony coming so I can see how my tunes are actually working. :)
One more thing Mike..... What do you use for the breech sela on the qb guns ?
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I've been using the 1/4 inch OD hard poly tube, the ID is .170. It's the same stuff they use for ice makers in the fridge, nothing fancy, cut it between 1/10 and 1/8 inch, to long and it will restrict the flow, to short and it will leak. At 9 cents a foot you can make a few screwup's and still not be out anything.
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On the subject of breech seals I have a full PCP converted QB which will produce over 38fpe, my emergency breech seal was the outer sheath from 3 core mains cable. Please dont laugh, it hasn't failed yet!
IJL
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thanks guys. I'm going tomorrow to get someof the poly tubing.
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The conversion is on hold for a little while. My father hasnt been able to find his small cutting tools for the lathe . So for now I have a barrel blank wihtout anything else.
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OK, the barrel is finished... the results as follows.....
610.2
588.3
605.3
606.2
608.1
603.1
604.1
598.9
599.8
601.2
average 602.5
spread 21.9
SD 5.862
max 610.2
Min. 588.3
This is with a standard valve, bolt drilled out, and hammer spring shimmed up. This weekend I'm going to change the valve to a modified valve and shim the spring up more. I will post the results later this weekend.
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What did you use for testing pellet wise, sounds good. For that last bit of ooph try an extended probe. It will use more gas but.......
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The pellet I used was benji sherdian .20 cylindrical 14.3 gr. I was thinking about do that, but I only get 20 shots per fill now. :)
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My testing of the .22 QB's gives about 30 to 40 more fps with the probe, could be alittle more with the .20.
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Mike,
How would I go about probing the bolt. any tips on this.
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First, have got a drill press? you can use a hand drill but it's nerve wracking. Look around the hood until you find one of those little flags that the lawn spraying companys use to warn you to stay off the lawn, sneak back late at night and get it. Or you can by one at the local farm supply store. If I remenber right they are just a bit over 1/16 inch in diameter so a 5/64th inch bit will work. Center the bit in the open end of the probe and drill in about 3/16. Cut the probe off just behind the hole and smooth the out side with sand paper. Stick the wire in the hole until it bottoms out and then measure from the shoulder of the bolt out 1 and 3/8 inch, mark and cut off, pull the wire out and mix a 2 part epoxey glue up and glue it in place. After you reassemble the receiver, bolt and barrel tweek it probe up/down side to side until it pushes a pellet smoothly into the barrel. Good to go.
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Thank you Mike. I just did the probe mod. it turned good fro my first :)
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OK, I haven't had the chance to do a chrony on the gun after the probe. To many honey do's going on :)
I will try to do some testing and give the results tomorrow. The gun shoots flatter than before, so I might have gained some FPS. We will see..
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Got some number for you.
1 670.40
2 682.70
3 694.00
4 700.00
5 682.60
6 682.50
7 706.90
8 717.60
9 707.80
10 738.10
min 670.40
Max 738.10
Average 698.26
Median 697.00
Spread 67.70
SD 20.17
FPE 15.49
The gun did a lot of fluxing between shots. After I ran these numbers my Co 2 tank was running low. SO I guess that's why.
any way The mod's are.
Bolt probed
Valve modified
This thing is loud :) , I have to find someway to quiet this thing down. I think a shroud is in order for this gun. I will probably get one from Larry R
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Hi Mike, Do you reckon tha the probe gives that much extra over the standard bolt or a re-drilled and relieved bolt?
Ian
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Wallis, I dont know if your local laws allow but the Webley Pro System sliencer helped enormously with my noisy QB but I do have to shim the orifice where the barell enters it to keep it on the straight and narrow :) BTW that "emergency seal" is still lasting!
Ian
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IJL - 7/18/2006 11:28 AM
Wallis, I dont know if your local laws allow but the Webley Pro System sliencer helped enormously with my noisy QB but I do have to shim the orifice where the barell enters it to keep it on the straight and narrow :) BTW that "emergency seal" is still lasting!
Ian
Unfortunately the laws here will not allow silencers on the gun. Glad the emergency seal still working out for you. I have to look into that.
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Here a pics of the gun. it's a carbine, accurate but loud :)
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Just got to thinking, how large is your port in the barrel, drilled to about .165 should help,
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Mike in iowa - 7/18/2006 8:41 PM
Just got to thinking, how large is your port in the barrel, drilled to about .165 should help,
I think my dad drilled it to 9/64 I will double check it.