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serenity 06-01-2007 04:45 PM

Is the only difference between an M4 upper and a mid-length upper the position of the fsb? Are they both 16 in.?

BrassMonkey 06-07-2007 08:52 PM

Yes the only difference is the position of the FSB. They are a 16" barrel and the gas port is still in the regular position, but covered by the handguards. The only advantage to the midlength sysytems like the Bushmaster Dissapator is the longer sight radius.

fpdsniper 06-10-2007 04:52 AM

I would add that another benefit is the longer gas tube, less wear and tear on the bolt from reduced pressures.


AR Hammer 08-05-2007 01:29 AM

I would also submit that,
Shorter gas tube also reduces the gas pulse timing so elevated pressures are not a huge issue.

Sight radius isn't an issue with the M-4 since the primary mode of sight is with optics now, not 'iron' sights.

Also, not all M-4 weapons have a 16" barrel, some special application rifles are shorter, depending on application...
M-4 is simply the military designation for the carbine version of the M-16 variant.

*Shorter than 16" in the civilian world is a violation of federal law with out proper BATF paperwork.

SabreArms 08-05-2007 05:49 AM

Am I wrong to say that M4's also have the Grenade launcher "dent"?

AR Hammer 08-06-2007 02:10 PM

Nope, the 'M4' most certainly have the indentation on the barrel for an M203, 40MM grenade launcher.

The early 'Carbines' didn't, but the M-4 has.

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