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4/1/2020 6:58:51 AM
Posted: 1/3/2005 11:03:08 PM EDT
What's the big deal about the M4 feedramps that I keep reading about? Why would the barrel extension on the M4 be any different than for the 20" AR? What bearing could barrel length have on the angle of the ramps in the barrel extension (I'm ass-suming that this is what is changed to make the extension be M4-compatible) - the cartridges sit in the same plane on every rifle, right?

I'm probably missing something very obvious...

Also, I assume that 16" dissipator barrels have their gas port drilled closer to the muzzle so that the gas system can impart a longer impulse stroke to the bolt, increasing reliability. That is the purpose of the dissipator, right? Why would you want the extra weight on the barrel - or is it primarily for the sight radius? Guess that wouldn't matter if you have mounted optics...
Link Posted: 1/4/2005 12:48:07 AM EDT
Read THIS for M4 feedramp info.
Link Posted: 1/4/2005 1:19:20 AM EDT
well... someone had to be the first person to bring up this subject for the new year (for the one millionth time)
Link Posted: 1/4/2005 10:56:31 AM EDT

Originally Posted By glockguy40:
well... someone had to be the first person to bring up this subject for the new year (for the one millionth time)



Well, that's okay. We all didn't develop our interest in this hobby at the same time, so you can expect people new to it to ask the same questions you did when you arrived.
Link Posted: 1/12/2005 12:03:46 PM EDT

Originally Posted By samsong:

Originally Posted By glockguy40:
well... someone had to be the first person to bring up this subject for the new year (for the one millionth time)



Well, that's okay. We all didn't develop our interest in this hobby at the same time, so you can expect people new to it to ask the same questions you did when you arrived.



Right thats why they play hit songs on the radio every 15 minutes (So that everyone listening gets to hear them)  
Link Posted: 1/12/2005 3:25:49 PM EDT
Here's a strange occurance. In my experiance, uppers with an M above the gas tube hole have the M4 feed ramps. I currantly have 2 uppers with the M stamp but don't have the M4 feed ramps!
Has anyone else here experianced this? Or is my previous experiance with M marked uppers a fluke.
Link Posted: 1/12/2005 7:44:22 PM EDT
I think you've been directed to the right link to get info on the M4 feed ramps.

As far as your question about the ports in a dissipator barrel, they are in exactly the same place as any other 16" barrel.  The barrel has a milled-off gas port at that point to keep the pressure correct for the 16" barrel.  There is then a regular front sight base at the point where it would be on a 20" barrel but it has nothing to do with the gas system.  It is put out farther to give a longer sight radius.
The advantage is the sight radius of a 20" barrel on a 16" barrel.  The disadvantage seems to be mainly that it looks "different".  It seems that people either love the look or really hate it.  
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