Author
Message
USMA-XC
Offline
Posts: 135
Feedback: 0% (0)
Posted: 4/25/2006 9:36:14 PM
I know that ARs fire from a closed bolt, but what exactly is the difference in operating principles between the two? What are the advantages and disadvantages of each? Thanks.
CK1
C&R Wanna-be
Offline
Posts: 642
Feedback: 100% (27)
Link To This Post
Posted: 4/25/2006 9:53:39 PM
[Last Edit: 4/25/2006 9:54:06 PM by CK1]
Quick and dirty explanation:

Closed bolt is more accurate, less moving parts as the bullet is fired, more consistent lock up, will contain high pressure loads very well.

Open bolt is hella simply and fast to cool, very easy to modify into full auto, thus the ATF will ream your ass sore for it. More commonly seen in blowback sub machineguns.
fla556guy
Offline
Posts: 1113
Feedback: 100% (25)
Link To This Post
Posted: 4/25/2006 10:05:28 PM
Closed bolt: When you pull trigger, the hammer hits the firing pin, causing the primer to ignite (ar-15, etc)
Open bolt: Pulling trigger results in the bolt going foward. The firing pin goes foward automatically when the bolt is all the way foward. (m60, etc)
RolandofGilead
Offline
Posts: 1103
Feedback: 100% (17)
Link To This Post
Posted: 4/25/2006 10:10:36 PM
full auto's are sometimes open bolt, SAWs M240s M60s and one particular model of the Thompson SMG (though I don't recall which) are all open bolt fired weapons.
olds442tyguy
Offline
Posts: 3137
Feedback: 100% (7)
Link To This Post
Posted: 4/25/2006 10:12:04 PM
[Last Edit: 4/25/2006 10:13:36 PM by olds442tyguy]
Open bolt has a fixed firing pin, where as closed bolt is hammer struck.

Say you had an open bolt handgun. When you fired a round off, the slide would lock back as if you had just shot the last round. When you pulled the trigger, the slide would release and the fixed firing pin would strike the primer as the slide came forward.
TCPilot
Armed Pilot!
Offline
Posts: 40
Feedback: 100% (1)
Link To This Post
Posted: 4/25/2006 10:33:47 PM
As I recall, the primary reason for an open-bolt action on sub- and machine guns is so that when you let go of the trigger, the chamber is empty & the bolt back; that way, after firing for extended periods, the risk of ammo "cook-off" is greatly reduced.

/TCP
Harv24
Online
Posts: 1474
Feedback: 100% (57)
Link To This Post
Posted: 4/25/2006 10:36:34 PM
Open bolts designs are most common with Sub machine guns and Belt feed weapons due to their Cyclic rate and the heat generated by the rate of fire. Open bolt designs keep a round out of the chamber until the firing sequence is intitated thus reducing the chance of a chambered round from cooking off in a hot barrel/Chamber

The Only Large Caliber MG that fires from a closed bolt is the M2 BMG.
rcr29
Offline
Posts: 59
Feedback: 100% (45)
Link To This Post
Posted: 4/25/2006 11:10:18 PM
The Thompson M1921/28 series and M1/M1A1 series of submachine guns all fired from the open bolt.
bigbore
Offline
Posts: 7637
Feedback: 100% (653)
Link To This Post
Posted: 4/25/2006 11:21:30 PM
[Last Edit: 4/25/2006 11:31:31 PM by bigbore]

Originally Posted By rcr29:
The Thompson M1921/28 series and M1/M1A1 series of submachine guns all fired from the open bolt.



Thompson



Heres a shot of M10. The bolt is open and ready to fire. The firing pin is machined into the bolt face, so as soon as it closes on a round in the chamber, it goes bang.


Imagine your bolt release is your trigger, thats what the trigger pull is like on these things.
Its the singer not the song. Spend your money on practice ammo. www.adcofirearms.com