GTA
PCP - HPA - C02 Gate => QB-7X Gate -W/Co2 & HPA => : jonny1o1 January 14, 2007, 03:22:03 AM
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ive read alot on qb mods and im getting one from sniper airguns in march or apri.ive read this
lhttp://www.gatewaytoairguns.com/library/Charlie’s%20QB-78%20Tune.htm http://charliedatuna.com/CO2TuneByCharlie.htm
thanks charlie
i think they are basicly the same and with doing the mods on one of these sites on a stock .22 qb 78 wht would the expected velocity be?
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I did some, but not all of the mods in the CDT QB78 tune guide. I was getting mid - high 600's from mine, but never got to chrony it on a day that wasn't either way too hot for CO2 or way too cold. It does shoot pretty danged hard though, and as I said I didn't do every mod listed. Here's a review of what I did,
http://www.gatewaytoairguns.com/airguns/forums/thread-view.asp?tid=763&mid=3789#M3789
You can also check Mike Melicks website. Look in the "tips" section, he has some good ideas there,
http://www.airgunartisans.com/flyingdragon/
As with all mods, be safe, CO2 is up around 850psi, it could put a serious wallop on ya!
Dan
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how many shots per charge do you get? i want alot of shots per cart along with good power maybe 550 600 fps
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shots per charge and fps go hand in hand. You make it faster, it eats more gas. Can't have both. I can't recall how many shots I get with mine, but it's not many. Too cold at the moment to try it out to tell you:)
Dan
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i know thats true but a balance of shots and power would be nice. like 575 fps and 50 shots or 650 with 40 shots. at the end of the working link lol my bad. it say from 680 to 725 fps. charlie or anyone else who did this mod , if you see this can you tell me how many shots you got per charge
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Hi, this is more than basic mods in my book but involved opening out the transfer port and polishing everything that moves and a few things that do n't!. also had the cocking block machined to reduce the hammer spring load. Gives 50+ full power shots then a few more as the gas runs out. 11.7 ish fpe but could go much higher.
http://www.gatewaytoairguns.com/airguns/forums/thread-view.asp?tid=947&posts=18&start=1
Ian
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not really alot on the mods.would i expect 50+ shots with charlie da tunas mod
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It depends how far you go with modding. The further you go with radical mods, the hungrier it gets.
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Aint dat da truth!
I say let it eat as much as it wants, then pick up the scraps later!
Dan
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Basic bone stock out of the box in .22 (velocity will vary from gun to gun but will give a starting point) RWS hobbie 11.9 gr. 481fps (some go as high as 550 out of the box)
Cleaned and lubed with barrel port and receiver port matched .170 transfer port seal installed 493fps
Bolt probe inlet drilled to .111 573fps shot count approx. 60
probe inlet and outlet drilled to 1/8 inch, 605fps shot count approx. 55
probe inlet drilled to .180 outlet drilled to .154 649fps shot count app. 50
the above numbers are with one cylinder shot count is for two cylinders
same as last with two cylinders 658fps ( using one cylinder seems to lower fps by 10 fps in most cases.)
wire bolt probe installed and two cylinders 689fps shot count approx. 40
open inlet of valve, taper head of valve, enlarge opening around head of valve in brass cap, taper end of pin and reduce head diameter of pin with bolt probe 705fps at 66 degrees shot count 35
as they say your results may vary
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so i think 50 is how many shots id want. i do all the mods above the mod with 50?
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yup, mike
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great
compared to a 2289 how hard is taking aprt a qb 78?
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Just as easy or easier, can't break anything when you do tear it down. I have a quick how to sheet if you want to send me mail........
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what about getting it back together? lol
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reassembly notes are there also.
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im kinda reviving this post but looking at this site in the theory of operation pages it looks the same as a 22xx with the valve and bolt and hammer with just slightly more peices. i have a 2289 so it looks the axact same with out the pump arm and stuff.
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same idea with the knock open valve, so many of the same mods apply. It's all about giving the air a clean unrestricted path to to pellet. The cocking on a QB compared to the Crosman 13XX and 22XX guns is backwards though, the hammer spring is compressed on bolt closing instead of when you pull the bolt back. I like it better actually, no chance of firing while loading, even if the safety is off.
Dan
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when you fire and the hammer hits the stem and so on when you said about the port that the port from the tube enters the bolt and out through the end right? thats why you drill it out?
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Sorry Jonny, I don't follow what you are saying. There's a tune guide here:
http://www.gatewaytoairguns.com/library/Charlie’s%20QB-78%20Tune.htm
maybe that will give you some of the answers you are after. Sorry I couldn't answer better, but I don't understand what you're asking.
Dan
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I think I have it, I think Jonny is talking about drilling out the bolt probe to increase the gas flow. Yup that works but the best results are gained by probing the bot, cutting the hollow end off and replacing it with a slightly longer, much thinnerand solid shaft.
Does that cover it?
Ian
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yupp, i dont think id want to cut it but i would drill it out.
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especially those of you I've made commitments to.
Due to a family illness I'll be very scarce and out of the UK until w/c 18/02/07
Appologies to anyone I'll be letting down
Ian