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Reloading Gun

What happens when the last round in an open-bolt gun (ie Uzi) is expended? Will the bolt lock back or forward?

I know that in a closed-bolt weapon, the magazine will usually cause the bolt to lock back, making it slightly quicker to reload (since the gun will not have to be charged again). But with an open-bolt gun, will the bolt stay backwards, or is it nessesary to pull the slide backwards after reloading? Or does it vary depending the magazine used? I know that some magazines in closed-bolt weapons will not lock the bolt backwards.

In most open bolt weapons (I.E Uzi, mac-X, M249, Etc) the bolt will travel forward and close on an empty chamber if the trigger is held.

In most closed bolt automatic weapons the bolt will either lock to the rear as in the M16 (sorry JD all versions of the M16 are closed bolt designs and all lock open after the last round)

Or close on an empty chamber Ala 9mm HK MP5

Yes it depends on the design of the magazine, specifically if the magazine follower has a tab or shelf to actuate a bolt catch.

The M16 does, as do most automatic rifles.

The .40S&W, and 10mm MP5s do and the new HK UMPs do

But the classic 9mm MP5 does not have a last round bolt
hold open, even though it fires from a closed bolt.

There are exceptions to both examples, but yes, you are right, the overall design of the weapon and especially the magazine matters most.

A weak magazine spring will sometimes allow the bolt to close on an empty chamber even in weapons with a last round hold open design.

First generation Glock mags are frequently guilty.

Also Uzi mags that have been notched for use in 9mm ARs or M16s usually do not lock open the bolt unless the follower has also been modifed.

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