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Posted: 4/20/2012 11:21:47 AM EDT
| I'm thinking about building my first AR, but see that some uppers specify "m4 feed ramps" etc. Whats that about? What kind of upper receiver should I be looking at to build an A4 style rifle? |
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Quoted:
I'm thinking about building my first AR, but see that some uppers specify "m4 feed ramps" etc. Whats that about? What kind of upper receiver should I be looking at to build an A4 style rifle? There are rifle ramps and M4 ramps. Sometimes the M4 ramps are called "extended ramps" because they extend into the upper receiver. Sometimes these receiver extensions are referred to as "M4 cuts" In the pic, upper left shows "Rifle feed ramps" upper right shows "M4 extended feed ramps". Pick out a barrel first and then get the correct receiver. The market is shifting toward M4 ramps but some good barrels are still shipping with rifle ramps. Don't combine that with a receiver with M4 cuts or you end up with the lower left "Bad" condition. |
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on an old rifle I built, although everything was "M4" ramps, things still didn't seem to line up just right inside the upper. What I ended up doing was cutting and polishing the ramps inside the upper to line up better with the barrel and mag. I don't suggest doing this to anyone though. Just buy an upper group that is good to go with M4 ramps.
Check out http://www.bravocompanyusa.com |
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While fondling my 10.5" upper parts while waiting on my tax stamp I noticed my barrel had shallow M4 cuts and the upper had deeper M4 cuts. (Didnt match, fit in the "bad" category according to the picture). Barrel is RRA and upper is DPMS btw. I marked the barrel extension with a dental pick to line up with the Upper cuts and started dremeling. I have read the barrel ext is very hard metal, maybe my dremel stone is super abrasive, but it only took about 10 min for both feed rams to be recut.
If you are going to do this be sure of your dremeling skills. I put the barrel in my vise padded with two small blocks of plywood, muzzle down. After every little bit of cutting put the reciever on to check, remark if necessary, then recut until you are happy. Polish with dremel when complete. YMMV. |
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Quoted:
While fondling my 10.5" upper parts while waiting on my tax stamp I noticed my barrel had shallow M4 cuts and the upper had deeper M4 cuts. (Didnt match, fit in the "bad" category according to the picture). Barrel is RRA and upper is DPMS btw. I marked the barrel extension with a dental pick to line up with the Upper cuts and started dremeling. I have read the barrel ext is very hard metal, maybe my dremel stone is super abrasive, but it only took about 10 min for both feed rams to be recut. If you are going to do this be sure of your dremeling skills. I put the barrel in my vise padded with two small blocks of plywood, muzzle down. After every little bit of cutting put the reciever on to check, remark if necessary, then recut until you are happy. Polish with dremel when complete. YMMV. Those were "Rifle Ramps" RRA does not use M4 extended ramps, as per RRA CS a few months ago. |
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