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Posted: 7/20/2009 12:44:23 PM EDT
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OK, I had a 12.5" upper assembled by a local smith (after proper ATF registration of th elower) and it works fine. BUT, the upper receiver feed ramps don't quite match up to the barrel extension. Like I've said it never caused an issue yet, but I haven't run it real hard yet...in a course or even at the range. Because it's something that may save my life one day, it just bugs me. I want em to match up perfect like my other ARs.
Anyway, because I've decided that I want a FF and a folding front sight (as opposed to an A2), I'm going to buy a new upper and send it in to a smith to have all of it done. My question is: Since I've shot it and I'll be using the same bolt and bolt carrier will it cause any problems between the bolt/BCG fit with the barrel extension when I matte them to a new upper (yes, I'll be sure the upper has the M4 feed ramps like the barrel extension)? I assume not, but just asking. *BTW I've already gone the route of addressing the local shop who said that if it works they don't want to fool with it. Well, won't ever have any more work done there  .
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Quoted: I am assuming you are reusing you existing barrel and attached extention. You should not have a problem with headspace if you do not have a headspace problem now. The relationship between the barrel/extention and the bolt should remain unchanged.OK, I had a 12.5" upper assembled by a local smith (after proper ATF registration of th elower) and it works fine. BUT, the upper receiver feed ramps don't quite match up to the barrel extension. Like I've said it never caused an issue yet, but I haven't run it real hard yet...in a course or even at the range. Because it's something that may save my life one day, it just bugs me. I want em to match up perfect like my other ARs. Anyway, because I've decided that I want a FF and a folding front sight (as opposed to an A2), I'm going to buy a new upper and send it in to a smith to have all of it done. My question is: Since I've shot it and I'll be using the same bolt and bolt carrier will it cause any problems between the bolt/BCG fit with the barrel extension when I matte them to a new upper (yes, I'll be sure the upper has the M4 feed ramps like the barrel extension)? I assume not, but just asking. *BTW I've already gone the route of addressing the local shop who said that if it works they don't want to fool with it. Well, won't ever have any more work done there .A few minutes with a small chainsaw file and a die grinder should correct the mismatch between your feedramps and barrel extention, it is very easy. Conventional wisdom states "M4 feedramps are only needed on a selectfire weapon with a short (high pressure) gas system." Paint your existing feedramps with machinist (dykem) blue, run the weapon. Were the extended feedramps contacted? I have done this experiment on a number of my rifles and carbines, I have yet to make contact with the portion of the feedramp cut into the upper receiver. All were semi-auto only. |
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