Open Bolt vs Closed Bolt firing...explain?
Bob
closed bolt position. Would somone please explain the differences?
How would the cartridge stay in the chamber if the bolt was open?
Please give examples also. I heard this at a shop and asked what it
meant, they didn't know so I'm tossing it out in 'puter land.
Thanks, Bob (ncl...@exis.net)
Gunfreak
#
#Some weapons are said to fire from the open bolt and some from the
#closed bolt position. Would somone please explain the differences?
#How would the cartridge stay in the chamber if the bolt was open?
#Please give examples also. I heard this at a shop and asked what it
#meant, they didn't know so I'm tossing it out in 'puter land.
Okay, Bob. I'll assume you're familiar with the operation of a
"normal" semi-automatic firearm. To load it, you pull back the bolt,
then release it, letting the recoil spring drive the bolt forward,
stripping a live round out of the magazine and shoving it into the
chamber. To fire the round you pull the trigger, which causes the
hammer to strike the firing pin (or releases the striker).
Now... here's how an open bolt gun works: To load it, you pull back
the bolt and.....woah! It sticks there! You'll notice a fixed firing
pin on the face of the bolt, and note that there's no hammer. When you
pull the trigger, the bolt flies forward, being propelled by the recoil
spring, strips a round out of the magazine, chambers it, and fires it.
The round is not fired prematurely because the ejector claw holds the
round forward of the fixed firing pin until the act of chambering
provides enough force to overcome the ejector claw spring.
So... on an open bolt gun, firing is done with the bolt literally open.
The cartridge can't fall out of the chamber because it isn't there yet!
Open bolt actions are pretty much used exclusively on submachine guns,
as they are simple, fast, and detrimental to accuracy (which usually
isn't that critical when you're spraying lead).
Various "assault" pistols have been made in the past which use an open
bolt action, but the BATF has put and end to that. If you find one,
it's usually many times more expensive than the gun's closed bolt
counterpart. Why? Think about it... An open bolt action's default mode
is full-auto fire. If the trigger sear wears off or the disconnector
fails (accidentally or otherwise) and doesn't catch the bolt in recoil,
the gun will fire full-auto.
Hope this clears the issue up for you.
Take care,
Mark Serbu
FSquid
#Some weapons are said to fire from the open bolt and some from the
#closed bolt position. Would somone please explain the differences?
#How would the cartridge stay in the chamber if the bolt was open?
#Please give examples also. I heard this at a shop and asked what it
#meant, they didn't know so I'm tossing it out in 'puter land.
Currently there are no semi-auto guns made in the USA that fire from an
open bolt ( BATF stoped that years ago due to there ease of conversion to
full auto). Although for some time there were semi-automatic guns made to
fire from an open bolt, almost all guns that use this system are fully
automatic. The action consists of a triger that holds the bolt fully to
the rear. When pressed the bolt moves forward stripping a round from the
magazine and forcing it into the chamber where it is fired by a fixed
firing pin (the pin doesn't move in relation to the bolt, but rather
always sticks out). Then the recoil moves the bolt back ejecting the
spent brass. This system was used in a great deal of Sub-machine guns for
two major reasons: 1) it allows the barel to cool more between bursts of
fire and 2) if the barel does get to hot ( some like the ingram SMG's
fire up to 20 bullets a second ) the rounds are not fired from the heat of
the chamber (called cook off). The big draw back is that with a half
pound of bolt slaming forward on each shot accuracy stinks, but at 1200
rpm who needs to be exact.
Hope this helps,
Navy Salt
James F Johnson
#Some weapons are said to fire from the open bolt and some from the
#closed bolt position. Would somone please explain the differences?
On closed bolt guns, the "ready" position has the bolt closed with a
round in the chamber. Pulling the trigger releases the hammer or striker
to fire the round. Subsequent to the shot, the bolt opens, extracts the
empty, and chambers a fresh round on closing.
On open bolt guns, the "ready" position has the bolt held open against
spring pressure, no round in the chamber. Pulling the trigger releases
the bolt, which chambers a round on closing, fires it (open bolt guns
often have no separate hammer or striker, just a firing pin permanently
affixed to the face of the bolt) and then returns to the held open position.
#How would the cartridge stay in the chamber if the bolt was open?
It doesn't. It stays in the feeding device until the weapon is fired.
#Please give examples also.
The military UZI, typical of a lot of submachine guns, fires from an open
bolt. The semi-auto civilian version fires from a closed bolt.
# I heard this at a shop and asked what it meant, they didn't know
Not surprised that they were talking about something they didn't know
anything about, pretty surprised they admitted it.
Jim Johnson
------------------------------------------------------------------------------
HUD secretary Henry Cisneros on "protected" guns and "sporting purposes":
"I mean, a 30-06 deer rifle with a scope is the kind of weapon that's in
use [by gangs] and the kind of weapon that was confiscated the other night."
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Ken Ogawa
#Some weapons are said to fire from the open bolt and some from the
#closed bolt position. Would somone please explain the differences?
#meant, they didn't know so I'm tossing it out in 'puter land.
# Thanks, Bob (ncl...@exis.net)
#
#
"Open Bolt" as referred to in some sub machine guns is such that the bolt
remains open when not firing. When the trigger is pulled the bolt moves
forward stripping a round from the mag, chambering the round and firing
usually by means of a fixed firing pin (UZI,MAC10). the recoil extracts
the empty case and bolt stays open, unless in full auto, then the process
repeats itself. This allows the firearms' cyclic rate to be very high as
there is no delay involved with the bolt closing and locking, and a
hammer falling on a firing pin. Open bolts in SMGs also help prevent
cook offs when extensive full auto fire is used since a round is not
chambered until it is fired.
Closed bolt arms refer to the type of firearm that when not firing has
the bolt closed and a round chambered. Firing a round is usually
accompished by means of a hammer and firing pin operated via the trigger
(M16, M60 machine gun).
Cook offs can occur after long periods of full auto fire when a round is
loaded in a very hot chamber, since the firearm chambers a new round
after firing.
--
_________________________________________________________________________
Just an insignificant bump on the log of the universe.
Arthur Sprague
#Bob (ncl...@exis.net) wrote:
##
##Some weapons are said to fire from the open bolt and some from the
##closed bolt position. Would somone please explain the differences?
##How would the cartridge stay in the chamber if the bolt was open?
##Please give examples also. I heard this at a shop and asked what it
##meant, they didn't know so I'm tossing it out in 'puter land.
#
Lots of Old Timey guns, like the BAR of my era, fired from the open
bolt position. The simple reason was that, in periods of heavy firing
(and we saw lots of those,) the barrel would get hot enough that if
a round was chambered it would cook off, converting the BAR to
an inadvertent full auto weapon. It was dual purpose, and would
fire full auto with the selector switch in the full auto position, but
we really wanted full auto only when we selected it and only for
the period of time we held the trigger back.
James Keane
: Some weapons are said to fire from the open bolt and some from the
: closed bolt position. Would somone please explain the differences?
: How would the cartridge stay in the chamber if the bolt was open?
: Please give examples also. I heard this at a shop and asked what it
: meant, they didn't know so I'm tossing it out in 'puter land.
The other responses to this question have been excellent, so I'll forego
the explaination and go straight to some examples.
Open-bolt action is mostly seen in full-autos, particularly big ones, to
prevent "cookoff" of a chambered round and also to allow airflow through
the chamber for cooling. An interesting hybrid is the CETME rifles,
which fire from a closed bolt in semi-auto mode but from an open bolt in
full-auto. The Swiss Oerlikon 20mm cannon, like most guns of its size,
fires from an open bolt.
Regards,
J. Sean Keane
Mark Bilger
#Closed bolt arms refer to the type of firearm that when not firing has
#the bolt closed and a round chambered. Firing a round is usually
#accompished by means of a hammer and firing pin operated via the trigger
#(M16, M60 machine gun).
..snip...
#Ken
#k...@maui.net
#
#Just an insignificant bump on the log of the universe.
Unless my memory is relly going, I remember the M-60 fires from
an open bolt position, too. Other than that, the explanation is
correct.
Mark "the nit-picker" @H-P
Eric Kozowski
#Closed bolt arms refer to the type of firearm that when not firing has
#the bolt closed and a round chambered. Firing a round is usually
#accompished by means of a hammer and firing pin operated via the trigger
#(M16, M60 machine gun).
Actually an M60 is an open bolt weapon. Your post is potrntially
confusing. Just wanted to clear that up.
Eric
--
Eric Kozowski Structured Network Systems, Inc.
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Colonel I. F. K. Philpott
In a closed bolt system the slide (bolt) closes fully, and the firing
pin is retracted behind the bolt face throughout the recoil cycle. When
the bolt is closed the sear releases the hammer to drive the firing pin
forward. This means that the minimum time after the bolt closes for the
next shot to fire is the lock time of the sear mechanism. In addition
this system requires a fairly heavy slide and strong recoil springs,
slowing down the recoil cycle.
In the open bolt system the firing pin is forward of the bolt face
during the recoil cycle and fires the chambered round momentarily before
the bolt closes, avoiding the delay of the lock cycle time. Furthermore
as the bullet fires the cartridge case begins to move back under recoil
forces and gas pressure, decelerating the bolt and starting it back,
thus the bolt can be much lighter and recoil springs weaker, and the
recoil mechanism is thus quicker.
--
Regards
Colonel Ian F. Khuntilanont-Philpott
Systems Engineering,
Vongchavalitkul University,
Korat 30000, Thailand
Dave Re
String1946 <strin...@aol.com> wrote:
#Open bolt is used on mostly on full-auto's so the chamber will stay
#cooler.
#The thought being that if the bolt stays closed on a live round while hot
#after
#a long string of fire that the round could "cook off".
Also, I beleive Open Bolt was used for a lot of subguns early on
because it's *much* easier to build an open bolt full-auto than a closed
bolt one. In it's simplest from, it only needs receiver, a cover housing
for the bolt and stuff, bolt w/ fixed firing pin, some kind of recoil spring,
barrel, and a trigger assembly that blocks the bolt when the trigger is not
pressed. Oh, and a magazine, of course :)
Really, this is essential what the MAC series of guns were, with some
refinements, of course.
Heck, come to think of it, Open Bolt Uzi's aren't much more than this
description, either.....
String1946
The thought being that if the bolt stays closed on a live round while hot