what is firing from an open vs. closed bolt?

H

hologon

New member
Not sure if this is in the right forum, but I see this a lot about subguns (and a post by Oleg...)

What is firing from an "open" vs. a "closed" bolt? What are the advantages/disadvantages of each?

Unfortunately, I've never had a chance to play with a rifle or shotgun, just handguns -- so my experience with bolts is limited to the bolt on my 22/45 or the slide on a 9mm (which I assume is equivalent to a bolt?)

Thanks!

-Jon
 
Let me see if I can make a fool of myself here. A closed bolt is just that - the firing sequence starts with the action closed, like you'd expect. The gun will have a hammer or striker held back by spring pressure that, when released by the trigger, results in the firing pin hitting the primer. This includes the double action, where the hammer/striker is retracted by the trigger stroke, then released.

On an open bolt system, the firing sequence starts with the bolt open. The trigger acts more like a bolt release - pressing the trigger allows the bolt to snap shut, stripping a cartridge from the magazine in the process. It's intentionally designed to "slam fire" - where the firing pin keeps moving forward on its momentum after the bolt closes. Closed-bolt semiautomatics (maybe autos too) have a spring that holds the firing pin to the rear to prevent this. When it gets weak, you can get unintentional slam fires - bad juju.

Advantages? Don't know - it would seem to be a simple way to acheive full auto fire.

Disadvantages - slow lock time (time from trigger breaking to bullet leaving). Not a big deal on a subgun.
 
Basically, the difference is that after the case is ejected, an open bolt gun will lock back. Pulling the trigger releases the bolt (w/fixed firing pin) and picks up the cartridge, chambers it, and then bascially "slam fires" which cycles and locks the bolt back again.

With a closed bolt gun, the round is chambered, and the bolt is locked in the closed position, with the firing pin in ready...pulling the trigger releases the hammer, thus striking the firing pin, thereby firing the gun. The bolt then cycles through and chambers another round, and away you go again.

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Shoot straight regards, Richard at The Shottist's Center
 
Yeah, what Jeff and 45King said. A closed bolt is backwards... or is the open bolt backwards? Depends on your point of view.

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Schmit
GySgt, USMC(Ret)
NRA Life, Lodge 1201-UOSSS
"Si vis Pacem Para Bellum"
 
Firing from a closed bolt is what you
are probably used to.

Which is to say that when the weapon is in
battery, the bolt is home, or closed. A hammer is cocked and ready to strike a firing pin.

Firing from an open bolt, the weapon is in battery with the bolt open. Pulling the trigger lets the bolt fly foward, chambering
a round, and locking, the hammer falls and
the so reality becomes more crystaline.
smile.gif


An open bolt weapon needs no "slide release" or bolt release, so changing magazines/belts is somewhat simplified. With a belt fed weapon a lot more comes into play regarding efficient machine design and function.
 
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by hologon:
Not sure if this is in the right forum, but I see this a lot about subguns (and a post by Oleg...)[/quote]

Hey, what did I do!?
biggrin.gif
 
Open bolt is for machinegun or subguns. Open bolt is a sure way to interupt the firing in the event the gun gets too hot and starts to cook off rounds. Release trigger, bolt holds open, no more fuel for the fire
wink.gif

That is about all the advantage it has besides being a very simple, inexpensive way to go.
The disadvantage is as someone else stated the extreme locktime which makes for very poor accuracy compared to a closed bolt design.
They are not always a "slam-fire". Some will have the bolt hit a trip lever just as it closes, releasing the hammer to strike the firing pin. This helps to prevent out-of-battery discharges.
 
With a full-auto weapon it is said to also aid in cooling the gun and preventing "cook-offs." An open bolt gun is a detriment to pinpoint accuracy.
 
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