After conducting a full teardown cleaning and reassembly of my Sigg 228, my hammer no longer stays in the fully cocked position with the slide off or on. The gun will fire and double action with no problem but will not let me cock the hammer to the rear. If I physically hold the hammer to the rear and use it a Cocker I can feel it positively engaging but it’s just not walking to the rear. I watched several YouTube videos and use my former military armors manuals to check everything but I don’t know what I missed. Any help would be appreciated

Also, the pistol worked perfectly fine in both moods prior to this is the first time I’ve taken apart in years.

Your hammer strut is positioned wrong.

The strut has two notches at the top.

If I am remembering correctly when you insert the strut against the hammer, while pushing up slightly the hammer will push forward when inserted correctly.

If inserted improperly the hammer will move to the rear.

Thanks in advance. I will take a look when I get home

Also one has a tendency to put the strut up into the frame and kinda hold it in place against the frame. This will be the wrong position.
You will need to hold the strut back away from the frame in the inserted position.
Then apply my as you push up on the strut it should move the hammer forward.

You can play with it with only using the strut if you have the 3 piece strut assembly ( metal strut, spring and plastic base). You can play around with its two different positions. With it forward towards the frame hit will push the hammer rearward..With the strut rearward it will push the hammer forward which is desired.

If your is the older all metal strut assembly thats one captured piece you can still do the same thing.

of course all of this is with the hammer in the de-cocked position

Yeah, a common mistake when reassembling. Even knowing this, I'll sometimes position it incorrectly. However, I always check the functioning before fully reassembling.

I double checked what everyone is saying and still no-go. Without the hammer spring in place (just the strut only) I can feel the seat engaging but by looking at it there doesn’t appear to be very much bite on the hammer if that makes sense. I will figure out how to post pics and see if that helps

I am just gonna admit that maybe I put something together wrong, strip it all down, and build it back up again.

Final solution.

I replaced both the hammer and the sear, good to go. When I put the new sear with the old hammer, hammer would not lock back. Old sear with new hammer, would not lock back. So, I replaced both and it runs like a champ now. FYI, I used a "lower" parts kit from Matrix Precision, so I figure maybe just used parts recoated. Anyway, no harm no would, it works now.