Thanks DJ ! You are correct about the coils for the trigger and bolt. The old combo spring is indeed used as the keeper and that is a bolt block taking up all the " leftover " space in the frame! Lol
The extra holes you see in the side of the frame are for pins that rest on flats ground on the trig/bolt screws to keep them locked in place as long as the T.G. and B.S. are in place. As for the left arm being longer I'll post a few pics to show how that happens.
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The bolt on the left is brand new the right one has been massaged a little. The left arm (to your right) of the bolt is some thinner that the new one. I should point out that even the new bolt has a thin left arm but they haven't always been that way. All of the reproduction parts had thick arms on both sides until maybe 10 yes ago when Uberti started making them just like the originals- thin on the working side.
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In this image you can see the left arm has been cut /clearanced to give it more length (where it meets the body of the bolt). It has also been clearanced for the working arm of the spring to lay "within" the bolt.
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Here the bolt head has been clearanced at the body junction and it gets back to full width right at the top (shiny area). This protects the edge of the notch since the "fitted " section of the bolt head is in the bottom of the notch . . . no contact of the edge with the bolt head.
There is also clearancing under the bolt arms for the trigger spring located on the trigger screwpin.
The extra length and thinness of the arm allows much more flexibility which translates to lifetimes of service. The necessary strength (in the vertical) remains basically unchanged.
Hope this helps some.
Mike