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Old September 4, 2002, 03:07 PM   #1
fastang50
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2 questions, paralax and m1/2 carbine

Hi all, two questions today. What exactly is meant by 'paralax' when talking about a scope? All I can figure is that it has something to do with the distance the scope focuses at? Is that correct? Second question, are there any good M1/2 carbine sights out there? I'm curious, the M1 is a good little short range gun, and I understand the M2 was an 'auto' version of the same. I understand the principal behind the mechanism of the M16, how was the M2 different from the M1? Again, curious. Doing too much thinking today I guess.
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Old September 4, 2002, 04:19 PM   #2
Johnny Guest
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Addressing ONLY the carbine question - - -

- - And probably providing much more than you wanted to know - - -

The U.S. Carbine, Cal. .30 M1 is a pretty efficient little arm, based loosely on the M1 rifle (Garand) as far as the bolt design and lock up are concerned. The RIFLE has a long, crooked operating rod, the front end of which is a gas piston. It runs beneath and to the right side of the barrel, and articulates directly with the bolt to move it to the rear. During this movement it rotates slightly, unlocks the lugs from the chamber area, and performs primary case extraction. The bolt then moves to the rear, doing secondary extraction, ejects the empty case, reverses direction, picks up and chambers the fresh round, on the way to lock up. The magazine is integral with the receiver using an 8-round en bloc clip to hold the cartridges for loading, and providing the feed lips.

The CARBINE has a captive gas piston beneath the barrel, which provides impulse against the front of the slide, which articulates with the bolt in a manner essentially identical to the that of the RIFLE. The CARBINE magazine is a separate, detachable box design, similar to those of a dozen oher firearms.

The trigger group of RIFLE and CARBINE are quite similar in function, though none of the parts are interchangeable. That of the CARBINE includes magazine catch and a rotary (usually) safety in front of the trigger.

The M2 version of the CARBINE has certain parts modified, and other parts added, to provide selective semi- and full-automatic functioning. The M2 has a selector lever on the left side of the forward receiver. When pushed forward, it allows engagement of a trip bar on the right side of the action with a machined contour on the slide. If the trigger is held to the rear after the first round is fired, and the slide goes forward, allowing the bolt to lock up, the rear end of the trip bar moves the sear in such a way as to release the hammer again. This process continues until trigger is released or the magazine is empty.

The M2 requires a different, or modified, stock to provide clearence for the different mechanism. The trigger group housing is also modified to accept the selector spring.

A conversion of the M1 CARBINE to M2 configuration is possible, given a group of the proper parts. It is also time consuming, and HIGHLY ILLEGAL, if proper government papers are not completed. You MUST have the papers (approved application with the appropriate tax stamp) in hand BEFORE such work begins. The government has refused to license any new machine guns for private possession for several years now, so, unless you are in some kind of government agency or in a foreign country, any such conversion is a no-no. I believe there was some sort of exception for LEGALLY REGISTERED M2 kits, akin to that for M16 and HK auto sears. I don't know the details. They may be found on the web in various places.

If it is a major issue, a legally registered M2 or M2 conversion may be located through a Class 3 dealer. Expect to pay good money for a mediocre machine gun. Rate of fire is very high and it is quite difficult to control in full auto fire. Some folks term the M2 a "Sound Effects Gun." It might make your adversary believe you have machine gun capability, and so have some intimidation value, but it is a much more effective fighting tool in semi-auto.

Best,
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Old September 4, 2002, 04:47 PM   #3
fastang50
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Thanks for the excellent mechanical description! Does anyone else have anything to add on the M1/2 front?

OK, how about 'paralax' next?
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Old September 4, 2002, 08:13 PM   #4
Buford Boone
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Parallax

Parallax, in layman's terms, is when the reticle moves on target as you move your eye position.

To check for this, place your rifle on sandbags, or some other sturdy rest, and peer through the scope, without touching the rifle or scope.

Move your head around. If the reticle stays in the same place, no parallax. If the reticle "dances", you have parallax.

Many scopes have adjustments for parallax. Many do not. The most common setting for scopes without parallax adjustments is 150 yards, provided the scope is still optically centered (20/20 vision). If you change the focus of the scope, you change the distance at which it is parallax free. This is why some people find the numbers on the parallax adjustment are not accurate for their scopes.

Parallax can come into play with head position. Head position is critical with a scope that is not properly adjusted for parallax. It is less important if the scope is properly adjusted.

Hope that helps.
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Old September 4, 2002, 11:26 PM   #5
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Buford Boone - - Glad you chimed in with that.

It clarified a lot of what I've read, and what others have tried to explain to me. I knew it had something to do with acope adjustment at various ranges, but was unclear on exactly what. Appreciate it.

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Old September 5, 2002, 08:25 AM   #6
fastang50
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thanks buford. I've seen scopes with an adjustment on the big lens (objective?), that's the paralax adjustment I assume? And I've seen some with that and an adjustment on the small lens (ocular?), that's the focus I assume? The scope I have on my 30-06 only has the focus adjustment on the small end.

Another question and observation. If the recticle is 'dancing' around, I assume this means I won't hit what I think I'm aiming at? It becomes somewhat of a shotgun thing, keep your head in exactly the same place relative to the bead/crosshair?
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Old September 5, 2002, 05:09 PM   #7
Buford Boone
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The adjustment on the ocular (End near your eye) is the focus. An adjustment on the other end, or on another turret, should be parallax.

Your scope does not have end-user adjustable parallax. The factory could adjust it (or Premier Reticle, if it is a Leupold).

How much parallax affects you depends on how bad it is. Try shooting all your groups without moving your head off the stock. Any deviation in the center of the groups could very well be caused by parallax. If there is no deviation, you are either placing your head in the same spot every time, or you are at the distance where your scope is parallax free.

If you really want to see parallax, try checking it at 25 yards.
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