Help: Can't stop Full Auto/Rapid Fire

[gunangel]

Hey guys,

A few of the vets on PBN were helping me out, but I thought I should ask this problem to a greater community for more feedback.
So...I just assembled a mag with an X-valved with ULT.

I had a Modded Sear, 9 shims, and a 950psi output tank and I was going full auto with my finger essentially resting on the trigger. I backed down to a normal sear, 2 shims in the ULT, and an 850psi output tank and I am still going full auto with a slight bit of pressure. I would like to have one ball per trigger pull, not two or three.

I tried an RT on/off and it still bounces, but I'd really like to get the ULT installed and working. As it stands I have inspected the sear a few times for defects, replaced the sear axle, replaced all the o-rings in the ULT on/off, retuned the level 10, dumped copious amounts of oil in the asa, and oiled each individual o-ring in the on/off and the marker still seems like it's set on full auto.

Any help would be greatly appreciated,
Thanks,
Brian

[longi]

Don't oil the on/off it will just exacerbate the problem. If your tank is adjustable drop the pressure further. If your using an Emag on/off pin , change it for an RT on/off pin. It's longer so it doesn't operate so fast. When you changes to the Rt on/off did you have the quad oring and the power tube oring fitted in the on/off?

[gunangel]

Thanks for the reply,

ah i'll stop oiling the on/off. the RT on off has an RT length pin and all the o-rings. It works but it has the miniscule amount of bounce (1 in every 3 shots will bounce) and the trigger is really stiff. i'm using an ans adjustable so i can hit roughly 700ish or 850. I have a dxs which supposedly is preset at 800 and the marker still bounced a great deal with that. I'll try drying the on/off o-rings and getting some of the oil off of it. I'd really like to use the ULT setup though.

[secretweaponevan]

Full auto and trigger bounce are two different animals.

Full auto is an on/off leak/problem and bounce is just bounce.

Try this:
With ULT installed, hold the trigger while gassing up the marker. If marker goes full auto with trigger held back, your ULT is not sealing due to bad o-rings, damaged pin (the sealing surface against the o-rings) or your "Modded sear" might be the gremlin.

For your sear, with safety engaged and marker gassed up, you want a 1/16" gap between the back of the trigger and the trigger rod (about the thickness of a credit card).

Post back and good luck.

Edit: If you have modified any of the contact surfaces of the sear (the top part that contacts the bolt or the on/off pin), go back to a stock sear until we get this problem fixed.

[Spider-TW]

ah i'll stop oiling the on/off. the RT on off has an RT length pin and all the o-rings. It works but it has the miniscule amount of bounce (1 in every 3 shots will bounce) and the trigger is really stiff.

Without air and after you have pulled the trigger, can you tilt the marker up and down and see the trigger rod move, maybe with just a little shake? I had sear that was binding and seemed to cause extra shots from a classic valve, which really "ain't right".

[gunangel]

With the RT on off the marker will bounce, I have to actually find a sweet spot. With the ULT if I don't do a really fast trigger pull it will let off two or 3 shots, with a slight bit of pressure it will go full auto, but will stop the moment I let go of the trigger (not a run away).

I am using a completely stock sear at the moment to address this issue.

I just replaced all of the o-rings in the ULT on/off, the top clear/white one, the bottom one, and even the little black one in the center. I did use a bit of oil so I have it out at the moment to let some of the o-rings dry.

The mag has a Zgrip on it, so the trigger pull is ridonculously long. I probably can get roughly 1/8 or more of an inch of distance with the safety on, but I will go and check again, you never know right?

Thanks for the suggestions! I will be posting later tonight with the results.

[gunangel]

played around with the pressure some, it's doing something fairly strange. the marker will gas up, when I pull the trigger a little bit (like literally a tiny tiny amount of pressure) the sear will shoot backward, then shoot forward and bounce off the trigger and fire again. It's fairly violent so it's catching me by surprise.

[Spider-TW]

Did you check the gap on the trigger rod like secretweaponevan suggested?

Sounds like the trigger rod is too tight or your sear is ground at a weak angle.

Is the rear thumbscrew hand snug or a little more? Whatever it is, pay attention to the tension and keep it consistent when you take it in and out.

[gunangel]

with the safety on i have approximately 1/8 of an inch between the sear pin and the trigger.

not really sure what ground at a weak angle means

rear thumbscrew is fairly tight (hand tight with a quarter turn with an allen wrench), i am using a temporary spacer at the moment though (using some electric tape since I have an old RT style grip frame on a RT pro style rail and valve)...hmm maybe that's the problem...i'll go buy something more permanent tomorrow but as of now yea...it doesn't seem to work and i'm all out of air

[maniacmechanic]

with the safety on i have approximately 1/8 of an inch between the sear pin and the trigger.

not really sure what ground at a weak angle means

rear thumbscrew is fairly tight (hand tight with a quarter turn with an allen wrench), i am using a temporary spacer at the moment though (using some electric tape since I have an old RT style grip frame on a RT pro style rail and valve)...hmm maybe that's the problem...i'll go buy something more permanent tomorrow but as of now yea...it doesn't seem to work and i'm all out of air

[Spider-TW]

That means you're not likely to get things working correctly with tape holding things together and if you did, it won't mean much later. As an example, ULT shims are 0.005 inches thick and you will have some number of 2 to 6. If the shims are not being squeezed down, you can throw in 0.001 (+/-) between every side, so a stack of 4 will have around 0.005 inches of compression needed to get it back to a fixed size. The difference between reactive and full auto on a ULT can be one shim (0.005 inches). A 10-32 front frame screw moves 0.031 inches per turn, or more than 0.005 inches per 1/6 of a turn (one side of a hex).

So you can't tune a ULT with anything underneath that is not rigid and the tension from the field strip screw has to be stronger than the pressure in the on/off, the stack of shims that may be in there, and any warping of the rail that has to be overcome.

On the trigger rod gap, 1/8" is large, but if the marker shoots then the gap is not causing a problem.

Sorry about the "weak angle". I ASSumed that you had modded the sear and that it had been ground (filed, polished, etc.) to an angle that wouldn't hold the bolt as tight as designed, giving it a weak grip on the bolt and allowing the bolt to kick the sear down after the initial movement of the sear.

[gunangel]

ah, well i have the rail bushing in there stabilizing the whole thing and I had enough torque on so i ASSUMED (yea i made a butt out of myself) that the torque on the bolt would push down on the rail bushing instead of the grip frame. The modded sear won't go in until I know my setup is working. No point in throwing another variable in there until all the other problems are taken care of.

Thanks for the help guys. I'm going to take a trip to the hardware store and see what I can find. I'm not patient enough for mail . Will post back with results, but the spacing in the shim thing makes a good deal of sense.

[Spider-TW]

Yeah, the rail bushing handles alignment of the frame, rail and valve, front to back and side to side, but it is not normally compressed.