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Mac10 open or closed bolt

chumchumchumchum Member Posts: 847 ✭✭
edited March 2014 in Ask the Experts
Hi, I'm not sure what the ad mean by this. I know it has to do with modifying it. Not my concern. I was just wonder how to tell between the two. Do you have to fire it, or is it something you can tell just by looking at the gun.

Thanks

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    fordsixfordsix Member Posts: 8,722
    edited November -1
    open bolt also known as slam fire has a firepin machined into face of bolt the closed bolt has a moveable fire pin like anyother firearm mac OB where last made in 1981 stopped by the gov.cause easy in conversion to full auto that is why those for sale start in the 1000.00 range while a CB is about 500 master piece arms makes a good CB mac type ..pull bolt back on OB and it stays back till you pull trigger..CB bolt is closed with spring loaded FP OB are good investment
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    GrasshopperGrasshopper Member Posts: 16,798 ✭✭✭✭
    edited November -1
    And be careful,,an inexperienced person can be dangerous with an open bolt model-
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    beantownshootahbeantownshootah Member Posts: 12,776 ✭✭✭
    edited November -1
    You can just look at the bolt face. If the firing pin is fixed onto the bolt you have an "open bolt".

    I couldn't find an image from a MAC-10 but here is one showing the difference in an Uzi, and it should be similar:

    http://home.netcom.com/~brownhen/sitebuildercontent/sitebuilderpictures/.pond/closeupboltfacemodified.jpg.w560h370.jpg

    What's the difference?

    With a traditional closed bolt system, when you pull the trigger, some sort of hammer or striker is released and it hits a firing pin, which then in turn sets off the round. With an open bolt system, the ENTIRE BOLT moves forward after the trigger is pulled, effectively turning the entire bolt into a heavy firing pin.

    Open bolt systems are typically only seen in machine guns and submachine guns. Advantages include simplicity/lower cost, better cooling (gun action stays open between shots), and no need to cock the gun when changing magazines. For this particular application, where you're more concerned about volume of shots than accuracy of individual ones, they're potentially good. As mentioned, the technique of actually using these guns is different than traditional ones (ie you don't charge them after inserting a magazine), so you do need to know what you're doing with one.

    Disadvantages include potential illegality (the BATFE doesn't like open bolt guns since they're typically easy to illegally convert to full auto), degradation of accuracy (increased "lock time" of gun since entire bolt has to move, not just firing pin, plus movement of relatively heavy bolt with forward slamming can throw gun off point of aim), and potential increased exposure of guts of gun to dirt from outside gun.


    quote:Open bolts are by far the easies to make things that youshouldn't have from.
    Maybe its more precise to say that amongst semi-auto guns the open bolt designs are some of the easiest to (illegally) convert to full auto.

    If all you want to do is create an illegal weapon and go to jail, then a hacksaw, shotgun, and ten minutes time should do the trick, and it probably doesn't get much easier than that! [;)][:p]

    In GENERAL, converting a legal semi-auto gun to a full auto can range from pretty hard, to trivially easy depending on the gun in question and your skill. Supposedly, you can convert some of the .22LR semi-auto "replica" type rifles to full auto just by swapping out ONE SPRING,and that's probably easier than filing a disconnector or doing some other such modification.

    IMO even apart from the blatant illegality and ridiculously high associated criminal penalty, this sort of conversion is sort of "dumb" anyway. My personal take on full auto guns is that they're sort of like "Cuban cigars". . .the mystique, scarcity, and illegality make the thing itself a lot more desirable than the quality of the actual item. If they were legal and readily available, interest would be substantially less.

    Furthermore, at least with some of these types of guns, just running the semi-auto version full auto will give you an insane cyclic rate of fire. EG, 1000(+) rpm, which will empty your 30 round stick magazine in under two seconds flat. Pistol type submachine guns can also be pretty hard to control with lots of muzzle rise and "spray".

    Optimally, what you want is select-fire where you can go either single shots or multiple (eiher burst, unlimited, or optimally both) based on an external control. THAT sort of conversion is usually fairly involved requiring real parts and/or gunsmithing. On top of that, then you want a folding stock and/or forward vertical grip to help control the gun during full auto fire. Of course both those things are restricted too, but something like THAT makes a potentially interesting/useful gun, IMO.
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    tsr1965tsr1965 Member Posts: 8,682 ✭✭
    edited November -1
    Another open bolt example is the Thompson 1927/1928, in machine gun form.


    quote:I was just wonder how to tell between the two.

    An open bolt gun, the bolt stays open untill you pull the trigger...that is why the firing pon is fixed, and the bolts are usually heavy, with lots of spring behind them.

    Closed bolt...the bolt is closed, when pulling the trigger...the trigger/sear, in turn releases a hammer to hit the firing pin, or a striker.

    Open bolts are by far the easiest to make things that you shouldn't have from.

    Best
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    charliemeyer007charliemeyer007 Member Posts: 6,579 ✭✭✭
    edited November -1
    http://en.wikipedia.org/wiki/M3_submachine_gun

    Open bolts have a chance to cool between bursts. The M3 I got to shoot was so slow I could fire it single shot even though it was a full auto only version. However, the rate of fire would increase rapidly when the trigger was held back. By about 9 rounds it was up to its full cyclic rate of fire. I was never able to hold the unit down and run a full stick burst due to muzzle climb.

    Perhaps the old Thompson trick would work. Unhook the sling at rear and then step on it to hold the muzzle down.
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    11b6r11b6r Member Posts: 16,588 ✭✭✭
    edited November -1
    One minor advantage of an open bolt gun- you do not have a loaded cartridge sitting in a HOT chamber after extended firing. That can produce a nasty surprise known as a cookoff- round fires without the primer being struck, due to heat. Used to be a problem with the older Browning belt fed MGs. The M-60 fired open bolt, no more cook-offs.
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    beantownshootahbeantownshootah Member Posts: 12,776 ✭✭✭
    edited November -1
    quote:Originally posted by charliemeyer007
    http://en.wikipedia.org/wiki/M3_submachine_gun

    Open bolts have a chance to cool between bursts. The M3 I got to shoot was so slow I could fire it single shot even though it was a full auto only version. However, the rate of fire would increase rapidly when the trigger was held back. By about 9 rounds it was up to its full cyclic rate of fire. I was never able to hold the unit down and run a full stick burst due to muzzle climb.

    Perhaps the old Thompson trick would work. Unhook the sling at rear and then step on it to hold the muzzle down.


    Chuck Norris don't need no unhooking of the sling! [;)][;)] (He's about to catch that hot cartridge in his mouth and eat it for a snack!)

    chuck-norris-uzis.jpg
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