Got a new Mag. ReTro Valve sputters and double shoots

I purchased from a local baller a very nice Minimag with a reverse-ported, level 7 Retro valve. It also came with a 3K Flatline.

When gassed, the valve either sputters or double shoots like those old Proline autoresponse frames, and shoots on trigger pull and on release. The valve has an on/off with a filed-down pin and the valve is one of the newer ones which accepts the ULT.

What I've done so far:
-I've cleaned the valve internals, cleaned and lubed the o-rings.
-I've tried the gun with the Flatline reg (set at 1000psi) and with a Ninja 68/4500 @ 850psi
-I replaced the on/off with short pin with an unmodified one I had in my parts box
-I tried a different sear/sear pin
-I tired the valve on a different rail/body/frame
-There's a leak when holding the trigger down, so I checked the o-ring and cleaned the cavity. No improvements.

Then I decided to check my on/off's pin length and that's when I saw something odd. It looks awfully short, it's .710 instead of the usual .750. The spare on/off I has an even shorter pin, so I dunno. Think that might be part of the issue?

I would say the on/off pin is a good place to start. Too bad you didnt post this up a couple of days ago, as I have an extra .750 pin sitting here that I could have put in the box along with the bike grip...lol.

LOL! Oh well, I PM'ed you over at BEO ;)

That short pin should be the source of the fire-on-release. You might be able to tighten the field strip screw down to help it. You can also try a thin brass washer on top of the top on/off o-rings to reverse-shim it. A quad o-ring will also make up the difference.

All of those are not as good a regular on/off with the right pin.

Interesting, will give that a try!

Otherwise, I've contacted Tuna for a replacement pin and an o-ring kit. Should be good as new after that.

*EDIT*

Tightened the thumb screw with an Allen key and that solved it. On/off pin is the culprit.

Tightening the thumbscrew would have squeezed the valve down a little tighter to the rail allowing the sear to push the pin farther into the oring.

It sounds like you have an emag on-off pin rather than a standard on-off pin. I think once you get a proper pin in there it will work fine without problems and won't need extra tight thumbscrew tightening.