GTA
All Springer/NP/PCP Air Gun Discussion General => European/Asian Air Gun Gates => China/Asian AirGun Gate => Topic started by: sr1sws on May 27, 2015, 10:08:47 PM
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I've looked around and it appears that the 'typical' QB7x RVA is drilled off-center to miss the bolt/screw tying the trigger group, air tube and breech together. I saw one that was described as drilled on center with bolts/screws entering from top through receiver and below - unfortunately there were no photos.
So, is there a 'how to' documented that I simply failed to find? If not, suggestions are greatly welcomed.
Oh... I did install a cock on opening mod that uses a tight fitting plastic (possibly Delrin) spacer behind the cocking block/spring guide. As it is very tight, it would seem that it should not cant under the off-center pressure from the typical RVA.
Thanks for any suggestions or tips!
Steve
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Hi Steve,
I am accustomed to the off-center RVA approach and have applied it to several QBs. If you prefer to do an on-center RVA, I will not attempt to talk you out of it. However, if you are looking into it on the basis that the off-center type causes the spring guide to cant and produces erratic velocity...well, that is not borne out in my experience. Just as an example, the 30-shot string that UCChris posted a few weeks ago was produced with just such an RVA:
30 shots
High: 857fps
Low: 853fps
ES: 4fps
SD: 1.38
That is consistency a $1500 rifle would be proud to deliver.
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Hi Steve,
I am accustomed to the off-center RVA approach and have applied it to several QBs. If you prefer to do an on-center RVA, I will not attempt to talk you out of it. However, if you are looking into it on the basis that the off-center type causes the spring guide to cant and produces erratic velocity...well, that is not borne out in my experience. Just as an example, the 30-shot string that UCChris posted a few weeks ago was produced with just such an RVA:
30 shots
High: 857fps
Low: 853fps
ES: 4fps
SD: 1.38
That is consistency a $1500 rifle would be proud to deliver.
Thanks Jason. Obviously the off-center version is much easier to pull off. I believe that's the route I'll go. ;)
Thanks!
Steve
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do you need the cock on opening mod for the RVA to work right?
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do you need the cock on opening mod for the RVA to work right?
I *think* so... maybe someone with definite knowledge can chime in. The native cock on close setup of the QB7x series seems weird - I'm not sure I fully understood it or why it would have been designed that way. Cock on open (the version I have anyway) would have only added 1 spacer but eliminated at least one machining operation and a pin.
In retrospect, it appears easy enough to do yourself, other than drilling the striker, which is surface hardened. Supposedly you can grind a flat through the case hardening and then drill it. I wanted a 2nd hammer anyway - as I flat-sided the new one and wanted to be able to go back to stock if it didn't work the way I wanted it to.
Steve
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You can use the helicoil setup as described here for a centered RVA. This makes a nice modification that I use on all my QB78 and 79 models.
http://www.gatewaytoairguns.org/GTA/index.php?topic=75939.msg722511#msg722511 (http://www.gatewaytoairguns.org/GTA/index.php?topic=75939.msg722511#msg722511)
Roger
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Sweet Roger, I'll check it out.
Thanks!!
Steve