Double fire with Colt 22 Conversion

[bigwagon]

A couple weeks ago a picked up a Colt 22 Conversion unit at a gun show. Judging from the box and instruction sheet, it was made around 1967 and is in virtually new condition. I doubt it's had 50 rounds fired through it, including the 20 I shot. The slide is essentially the same as a Gold Cup with the raised top rib, angled serrations and Accro rear sight, which makes it a perfect match for my 1966 National Match Gold Cup. Anyway, this week I fired it for the first time using my Series 70 Gov't Model receiver and it double fired twice on the first magazine, and then again on the second, which was all I fired it. There might have even been a triple in there! The Series 70 has never done this, so I am assuming the situation has something to do with the conversion unit. Any ideas?

[RickB]

I suspect something involving the disconnector and how it interacts with the slot cut for it in the slide. Try dropping the hammer (on an empty chamber, of course . . .), then while holding the trigger fully to the rear, rack the slide. Now, release the trigger, and listen for a distinct "click" as the disconnector pops up and the sear resets. If you don't hear it, or if it sounds/feels different each time, there's perhaps a problem with the location or depth of the slot in the slide.

[John]

RickB has it right. It's probably the disconnector.

[bigwagon]

Thanks for the tip. I checked it and the disconnector works normally when hand cycling, although I did notice that the notch in the slide is shallower at the front than the one of the 45 slide. Something I didn't mention is that I was firing low-velocity Federal Gold Medal target ammo, so I wonder if light recoil was somehow causing trouble with the disconnector. Shouldn't a shallow disconnector notch cause it to not release the hammer if the disconnector is not resetting when the slide cycles? If there is a problem with the sear or disconnector itself, it seems like I would have the same issue with the 45 top end.

[John]

Yeap, that's strange. If the notch is too shallow, it shouldn't create a double-fire problem. Unless the disconnector in its new position (more downwards than before) binds with the sear and does not allow it to cycle back enough to engage the hammer hooks. Take off your disconnector and make sure the area around its hole is free from scratches or burrs.

Also make sure that the disconnector cut is at the same position (length-wise) on both slides.

Since this is more of a gunsmithing question, I'll move it in the Gunsmithing forum, maybe 1911Tuner will see it and jump in.

[gbw]

I have a Day Arms .22 conversion unit that double fires. Weak FP spring, and roughness that prevents the FP from retracting all the way after firing.

[robot1911]

Using that light, SV ammo it's possible the slide isn't recoiling far enough to completely cock the hammer and it's following the slide forward...but not catching on the halfcock notch.
Does the slide lockback after the last mag round?

Bob