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Well I spent yesterday and last night working on my 9mm Semi Auto but need some help to get the most out of it.Im running=
1/4" QEV VALVE.
1/8" Poppet Valve( normally open, as pilot)
13" aluminium Barrel just over 9mm ID.
Spring Tensioned Ball Detent.
Plunger/Spring set up.
this is constructed as per diagram(first post,page 10) on Jacks " I has Full Auto" thread with ball detent and air coming in from (under) the bbs.
1)will my 1/4" QEV be good enough for this set up/ calibre?.
2) unsure of what size air chamber to run( 3/4" but how long?).
3) when I hook up the air to my gun the qev fires off!!??, can I stop this?.
I tested this at work today but forgot the qev fires upon hook up!, the bb chamber had 2 rounds in it and the plunger/spring with no endcap yet( was using a rag to plug the end earlier at home. I conected the air and it fired the spring/plunger and the second bb out the back,all of which I never found ,before all this id did seem to feed correctly though! . Current air chamber is tiny (3/4"ID X 5" long) as it was from a previous gun so using it to test feeder out,its just too unsafe with the qev firing after the air is conected so I must fix that somehow?? and make a much larger Air Chamber. pics soon
Last edited by django on Thu Apr 30, 2009 8:10 am, edited 3 times in total.
1)1/4" QEV is surely okay for that calibre.
2)With air chamber you mean the chamber attached to your QEV? It should be okay, chamber size doesnt matter that much.
3)This probably depends on your pilot valve. I guess that the chamber fills, and the poppet valve then pops open pilotting the gun. You need to hold the pilot valve closed in order not to fire.
What pressure are you running at and what are your perfomance expectations? If it's reasonably high, say around 200 psi, you should get fairly good performance from a 9mm calibre fed by a 1/4" QEV, even with such a short barrel.
As to the premature QEV firing are you filling from the chamber side or the pilot side? Have you added a spring to help it reset?
Damn this sucks!!!!!,I have it all together now and for some reason will fire one and the next round then rolls out the barrel!?. Ive tried adjusting the ball detent hard and soft but it keeps doing it, if you adjust the detent too hard the bbs dont come out even at 120psi this is the problem ive had for years with semi auto,it allways doube feeds .
The spring on the BB Plunger is pretty weak so I dont think its forcing the bbs to the barrel too hard, im only using 5 bbs too(can take 10) so should'nt be too much force on the spring.
JACK:only running 120 psi(compressor) until I fill my co2 bottle, but still trying to get it work correctly anyways,filling from the pilot side, no added spring in the QEV but a good idea I'll get onto.
I should think it would preform better power wise with a bigger chamber(its tiny!) and unsure if the 1/8 Poppet valve should be replaced with a bigger version perhaps?.Im buggered if I know why its double feeding ARGHHHHHHHH ,DAMNIT
EDIT: I just tried it out without the spring+Plunger and it works without it but struggles to fire the last 1 or 2, the bb plunger I made reasonably tight fit to take up dead space when bbs are being used up and to feed them in at all angles.Without this inplace I can notice a power drop though so unsure of where to go from here?, put a hole in the middle of the plunger?........
Yes, you could try leaking air through the magazine on purpose by making a hole or leak in the back. This leak will lose some air, but that air will push the bb's back.
I fitted a light spring to the Qev internals and it no longer goes off when connected to air( one prob fixed),id rather not lose any air at all and dont know if that hole in the mag cap will help anyways?.I think its because the second bb is so close to the first and the burst of air running through is not a short enough burst so the second bb follows the first when the ball detent is depressed.
if theres any pressure pushing the bbs to the detent(ie weak spring) the second bb rolls out,see I tried again a few times again with no spring and it works but as soon as theres pressure pushing the bbs forward the next rolls out. this is using a very loose plunger and weak spring,may need the plunger(bb pusher) even smaller and as weak a spring as I can find to fit?. I had an extremely weak spring at work for this purpose but it went flying and lost it, failing this it'll need a BB Interuptor firing upwards from the air inlet( as SPG posted on another thread).
The only reason Ive not done so is ,that bb interuptor will hard to get right and also will be slamming upwards against the roof of the bb chamber which is only aluminium.Man ive gotta get this thing to single feed!!
Maybe the position of your interrupter is wrong. Maybe it should be placed some more to the back so that the 2nd BB will not have room and thus stay back.
Can you post a diagram with the exact dimensions and components of your magazine and breech setup? There might a slight detail you're missing somewhere.
Sorry cant post a Diagram,I'm too computer illiterate to do so BB's are 9 mm,the ID of the barrel/mag is about 9.5m,the exact middle of the air inlet is right inline with between the first and second bb( air inlet is the same size 9.5mm tube as the rest of the gun.Mag is 115 mm long(4+ 1/2") the barrel and mag are all the one tube with the air inltet and ball detent tube stuck onto it and a threaded mag cap at the rear.
the Ball detent consists of a 6mm bb( lower bb,DETENT),small med strength spring then another bb ontop of the spring, above the top bb is a nut and a bolt that threads into the nut to adjust spring tension by pushing the top bb down these are housed in a small brass tube and steel puttied inplace as is the air inltet tube.Maybe the 6mm detent is not large enough to cope with stopping the second 9mm bb from rolling out??.
the best I can diagram wise is that this is made just as pictured in page 10 of your "I has Full Auto" Thread( first post,page 10) theres is no BB inertuptor in the air inlet as posted later on in page 10 by SPG. The reason I havent made one as yet is,im pretty sure the force of the bb interuptor flying upwards will hit (hard) against the top of the mag wich will wear away the top of the mag,bend up the interuptor and by damaging the top of the mag the bbs eventually wont roll forward to the detent, unless some sort of rubber one could be made but I dont it could be constructed to the required shape needed............
Last edited by django on Tue Apr 21, 2009 4:51 am, edited 1 time in total.
Maybe it is too far to the front, allowing the second bb to get sucked up and blown trhough.
A diagram or pictures would really help...
yeh as I said the middle of the Air Inlet is inbetween the first and second BB, maybe if it was set up so the BB Detent was further back enough so the first round was directly covering the air inlet instead?.I just tried something else and put a spring in the air inlet so when the qev fires it pushes the spring upwards and stops the second bb, it fired only one round as I wanted but on the second fireing nothing hapened?. I looked inside and found the spring had pushed right through and into the barrel( Spring forming an L) so it was no good= I think I'll have to alter the detent position and hope it works??..............
This can be an issue as air is free to move behind the BB in the mag and push it out.
Ive just stuffed it up and had to cut off the mag end of the gun, im starting over again but using the same length of tubing meaning the barrel will be small but just trying to get a semi operational for now anyways.
Am I better locating the Ball detent so that the 9mm BB is covering the Air inlet or further back than that even? so the first half or the first bb is covering the air inlet?.I'll finish it off tomorrow as it getting late now .
And Jack I see your point of my mag's ID size being an issue pushing bbs forwards from air behind the bbs and probably why I had the problems with it? but I'll try again tomorrow, sigh!.....................
EDIT: also the air inlet hole I drill into the main body going into the mag area is 8mm,large enough for flow and small enough to stop the 9mm bbs rolling down the air inlet,could this be causing probs too?,should I be drilling this hole smaller?.
I would point to this being the source of your problems. Barrel and magazine tightness in relation to the projectile is critical to the operation of a Tee type breech.
Well this has allways been a problem for me all these years making BB guns= ive never been able to get hold of suitable tube for a specific ammo size that fitted perfectly with no blowby....
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