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Discussion Starter · #3 ·
R4 is what RRA calls the barrel with the M203 cut, the rest of the world calls it a M4 barrel ;)

the difference is the cutout for the M203 grenade launcher, which is better ? the one you like the looks of :D
 
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Discussion Starter · #4 ·
http://www.rockriverarms.com/item-d...age=bblr407.gif&CFID=6373035&CFTOKEN=27100757

I figured it was an RRA-only term, so this is the "real" M4 barrel? Is there any worry with a mid-length rail because of the indentation towards the muzzle?


If you look at the pictures, the lightweight barrel is obviously not flat along the outside (some areas are higher than others). Is this anything to worry about as far as uppers or rails? What is the purpose of these changes in diameter?

Thanks!
 
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Discussion Starter · #5 ·
http://www.rockriverarms.com/item-d...age=bblr407.gif&CFID=6373035&CFTOKEN=27100757

I figured it was an RRA-only term, so this is the "real" M4 barrel? Is there any worry with a mid-length rail because of the indentation towards the muzzle?


If you look at the pictures, the lightweight barrel is obviously not flat along the outside (some areas are higher than others). Is this anything to worry about as far as uppers or rails? What is the purpose of these changes in diameter?

Thanks!
Nope not a real M4 barrel, those are made by Colt and are 14.5" in length

Midlength rail will fit

The cutout is where a M203 connencts, the barrel is not flat, to save weight .
 
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Discussion Starter · #6 ·
With a 16" M4 barrel, can you not use a mid-length handguard, such as a quad-rail free float?
 
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Discussion Starter · #7 ·
With a 16" M4 barrel, can you not use a mid-length handguard, such as a quad-rail free float?

yes you can, and example would be the Samson MRFS-CS-EBR to use with the standard FSB or you could use any 10" rail by changing out the FSB for a gasblock and then putting a front sight on the top rail.
 
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Discussion Starter · #9 ·
If the area in the red box is what you're talking about I would think that the thicker barrel would be more accurate and would warp less when hot thus staying accurate after being shot several times.

 
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