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Discussion Starter #1
I have what I hope will be a quick question to answer.



Lets say you have a car length AR and wanted to switch to a mid length ..... what would you need to do it and how easy/hard would it be.



From what I've found one would need a new mid lenght handgaurd and gas tube ..... is there anything else assuming that one size fits all in the ways of the handguard cap?? Maybe new handguard liners??



And would it be as simple as removing/moving the gas block & current handguard/gas tube and just putting the new stuff on??
 

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New barrel!! You are most of the way there but, the hole in the barrel on a carbine will be too far back.
 

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Discussion Starter #3
coltman1985 said:
New barrel!! You are most of the way there but, the hole in the barrel on a carbine will be too far back.


here's a totally noob question ..... what "hole" Your not talking about the notch in the barrel pointed out in the photo are you??



 

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"The Armalite Mid-Length Carbine was designed specifically to overcome the long-known gas system-related problems associated with the standard M4/M4A1, problems that have been plaguing end-users for years. These include greatly accelerated gas port erosion, , excess heat, higher operating gas pressures, melted and blown-out gas rings, and an open/iron sight radius that's too short. None of these are good things on a field combat weapon.



So, how does the the Mid-Length Carbine mitigate these problems? The Mid-Length Carbine moves...



the front sight base/gas block 2 inches forward from its position on the M4/M4A1 Carbine. This puts the Armalite Mid-Length Carbine's gas port mid-length between that of the M4/M4A1 carbine and full-length AR-15/M16 rifle, thus the Mid-Length Carbine's name."



http://www.defensereview.com/modules.php?n...cle&sid=360
 

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Just buy a new upper already built. Simple. Then you have a choice to fit the need.
 

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Discussion Starter #6
Puffy said:
Just buy a new upper already built. Simple. Then you have a choice to fit the need.


No need, I think I managed to work everything out. I had origionally placed an order for a mid-lenght but it's been awhile with no signs of it coming any time soon. So I was just trying to come up with options ..... was going to see if I could get the short lenght and if I didn't like it just convert it to mid but that doesn't seem practical. But I managed to find another mid from a different company and had them order that one and cancel the first order. So I should have it in a week, I'll prob explain the whole story when I get it & post pics.
 

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greatzippy said:
[quote name='coltman1985']New barrel!! You are most of the way there but, the hole in the barrel on a carbine will be too far back.


here's a totally noob question ..... what "hole" Your not talking about the notch in the barrel pointed out in the photo are you??



[/quote]



No. There is literally a hole in the top of the barrel--the gas port. That is where the high-pressure gas--the same gas that pushes the bullet--is bled off through the gas block and up the gas tube to push the bolt carrier back, hence a "gas-operated" rifle. You cannot simply drill another hole further down the barrel, put on a new gas block and longer gas tube. You would be left with the original gas port hole and no safe way to plug it (at least that I know of). We're talking about 50,000 psi here!



Now if you were just wanting the longer handguards, longer sight radius, and the mid-length look, you could put on a "low profile" gas block--keeping the carbine length gas tube--that fits underneath longer mid- or even rifle-length handguards, and put on another front site base/gas block further down the barrel. But then you would not be getting one of the greatest benefits of the mid-length AR which is a smoother, more reliable gas system.



I hope my explanation wasn't too confusing.



I've been spending a lot of time over at AR15.com lately, as I'm looking to get an AR myself. I've owned full size 20" AR's and 16" carbines before but this time I'm definitely getting a mid-length. Unfortunately, S&W doesn't offer one.
 

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The mid-length gas system is 2" longer than a carbine gas system and runs lower pressures which fix the overgassed situation.



Gas pressures at the gas ports in the barrels:



Rifle length gas system pressure is (about 13.5K psi)

mid-length gas system pressure is (about 19K psi)

CAR gas system pressure is (about 26K psi)



Gas pressures reaching the bolts are:



Rifle = 1K psi

mid-length = roughly somewhere between the rifle and CAR

CAR = 1.5K psi
 
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