Closed Bolts

 

 


The most common configurations that people see on UZI's are open bolts on full autos and closed bolts on semi autos, but it doesn't have to be that way. Full auto Mini UZI's and Micro UZI's can be found in either open bolt or closed bolt configurations. However, a closed bolt for a full auto is not the same as a closed bolt for a semi auto. Here's a comparison of two original IMI bolts - a full auto closed bolt and a semi auto closed bolt for the Mini Uzi. Converted closed bolts are also available.


Here is a picture of the right side of both a semi and full auto closed bolt for the Mini UZI. Note how the ejection port on the full auto is smaller. Also note that there is no need for sear relief on the right side of the bolt since there is no sear pad on the right side of a full auto Mini closed bolt sear. It's strange that there is a sear relief on the semi bolt since the semi sears in the Mini UZI also had no right side sear pad.


There are a number of differences around the bolt face of the semi and full auto bolts:

1. The full auto bolt has the lower rim at the bottom of the bolt (fully supported) while the semi does not (partially supported.) Trying to use the semi bolt without the lower rim in a full auto will usually result in light primer strikes.

2. The semi extractor's claw is not symmetrical. The full auto extractor has a larger gripping surface.

3. The semi bolt is relieved above the bolt face to accept the barrel restrictor ring that is part of the semi feed ramp.

 


Another angle showing the fully supported bolt face on the full auto vs. the partially supported bolt face on the semi. The lower rim of the bolt face is milled off of the semi bolt.


Looking at the left side of the bolts shows that the firing pin safety trip is slightly different. They are so slightly different that they are probably interchangeable.


Looking from the rear, there is not much difference. You can again see the sear relief on the right side of the semi bolt.

 


The full auto firing pin carrier/recoil springs are the same as the semi.


The full auto open and closed bolt assemblies side by side. Note the difference in ejection ports, the difference in sear cut outs and the "feet" that the open bolt has on the front of the bolt..


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