Who has added an SRT kit to their Norinco NP22? Double action problems.

[Grizzlypeg]

I put a Sig srt kit in my NP22 and now it won't reliably shoot double action. What I observe is that the trigger bar is pulled downward so far when the hammer is at the peak of cocking in double action (which can't be a change, because the SRT kit would not have changed that), that the trigger bar rides under the sear, just like it would if it was being pushed down by the disconnect. The falling hammer is caught by the sear but not released by the trigger bar's forward movement. As a result it lands on the sear and doesn't fall forward.

In single action, the SRT kit works just like it should. But in double action, 4/5 times it won't go bang. The hammer drops onto the sear, and sear isn't triggered by the trigger bar's tab. The tab on the trigger bar instead goes beneath the sear's projection. This happens whether the slide is on or not.

The difference might be the Norinco trigger bar spring isn't the same, not strong enough to hold it upwards as the hammer comes over the peak of rearward draw, or it might be that the Norinco trigger bar itself is slightly different on the real sig. There can't have been any change in the double action itself from adding the SRT kit, as only the hammer and trigger bar come into play initially. Only change by adding the SRT is the sear itself, and the safety lever. One thought is that the srt sear and safety bar are slightly wider and that might cause some binding, but I can't see how that could affect the position of the trigger bar. If I apply slight upward pressure on the trigger bar as I pull the trigger double action, the problem does not occur.

I'll pull the parts and mike the width of the SRT sear and safety bar and compare that with the OEM Norinco sear and safety lever. Maybe the sig one is wider and there is a clearance problem? I'll also observe how the old one works and why it doesn't ride under the sear.

 

[Grizzlypeg]

Having re-installed the original norinco sear and safety lever and watched its operation, and then re-installed the sig SRT sear and safety lever, the problem is something very subtle. If I apply slight upwards pressure on the trigger bar as I pull back the trigger in double action, the problem does not occur. So, either its the trigger spring on the norinco is too weak to hold the trigger bar upwards, or their is some slight difference between a Sig trigger bar and Norinco trigger bar that makes the difference.

So, the dilemma, is it worth buying a Sig trigger bar and spring to possibly have the SRT kit operate in double action? I can either reinstall the norinco parts and have double action, or leave in the Sig SRT and have better reset, but no double action. Personally, I can't see using the double action much, but having it function right, just seems, right.

 

[Grizzlypeg]

I made a discovery. When I reassemble the gun using the oem sear pin, it fails to fire double action using the SRT kit 9/10 times. However, if I replace the sear pin with a pin punch, and try it, it works 50/50 times. It's clearly some problem to do with subtle tolerances of the parts. I'm going to make up a replacement sear pin, that fits tight in the frame at the ends, but is slightly reduced diameter in the centre, and see if that solves the problem.

Edit: Made up a pin with the right diameters at the outer ends where it passes through the receiver, and .025" smaller in the middle where the sear rides on it, and the problem is fixed. Now that I know what the fix is, another solution would have been to open up the hole in the sear slightly, but its always better to modify the cheapest part. It now works 100% of the time in double action. No idea what is actually wrong, but it must have something to do with minor differences in the dimensions between a real Sig and an NP22. Having reduced the diameter of the pin, its impossible to say whether its the SRT sear itself, or the new srt safety lever, both of which ride on this pin, that are causing the problem.

 

[toxic]

Glad we could help you solve your problem.

Good to hear you got it sorted out.

 

[Grizzlypeg]

The replacement pin I made up eventually bent, resulting in a light hammer strike and failure to fire 2/10 times. I swapped back to the original pin and original np22 sear and safety lever, and the problem stopped. So, unless you can fashion a hardened pin, I don't recommend narrowing the pin. Perhaps enlarging the hole in the safety lever would be preferable, but I hesitate to, as that will permanently alter the part.

 

[call2arms]

The replacement pin I made up eventually bent, resulting in a light hammer strike and failure to fire 2/10 times. I swapped back to the original pin and original np22 sear and safety lever, and the problem stopped. So, unless you can fashion a hardened pin, I don't recommend narrowing the pin. Perhaps enlarging the hole in the safety lever would be preferable, but I hesitate to, as that will permanently alter the part.

Can a replacement pin be made from a cut off drill bit? They are hard and available in many sizes

 

[Grizzlypeg]

Can a replacement pin be made from a cut off drill bit? They are hard and available in many sizes

It was made from the shank of a drill bit. Seems they don't harden the shanks. You can bend one quite easily. Or mark one up from slippage in a chuck. It must be intentional, to preserve the chuck.

 

[Meroh]

It was made from the shank of a drill bit. Seems they don't harden the shanks. You can bend one quite easily. Or mark one up from slippage in a chuck. It must be intentional, to preserve the chuck.

Drill shanks are always softer. I would suggest a replacement spring. Increasing the tolerance is a band-aid remedy, especially when there was no interference fit from the original. A spring should be cheap enough, and available.

 

[Grizzlypeg]

Drill shanks are always softer. I would suggest a replacement spring. Increasing the tolerance is a band-aid remedy, especially when there was no interference fit from the original. A spring should be cheap enough, and available.

If a change in the trigger bar spring fixes it. Maybe, maybe not. I'm still not sure what causes the trigger bar to miss the sear in double action when the SRT kit is installed.