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Posted: 2/23/2004 6:07:14 AM EDT
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I have a Bushmaster barrel and a flat top upper from Del-Ton with the feedramps. Got a buddy to put them together (don't have the tools....yet) and the feedramps do not mate up with the feedramps in the barrel. It appears that in order for the ramps on the upper to match the barrel ramps, the ramps on the barrel would need to be ground down a bit. Is this common? What is the best way to grind down the ramps on the barrel and have them come out to be the correct width and be smooth in the end? |
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Yes, this is quite common. You have several options, you can send it to somebody like Kurt's Kustom (see the "Industry" forum) and he'll fix her up for ya, have it done locally by an AR15 gunsmith or pull out the Dremel tool and straighten the cuts out yourself. Mike |
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Thats just great. I have the same parts BM barrel and Del-Ton flat top upper and the Barrel ext. ramps overlap the receiver ramps quite a bit, same thing with a RRA rec. The problem now is once you hone the barrel ext. will the barrel always have to have a feed ramp upper if you decide to change the upper? G-Man ô¿ô |
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I used a dremel tool as recommended by mr_wilson and all that needs to be done is the receiver ground down to be flush with the ramps on the barrel. It shouldn't matter what upper you place the barrel on after that, because all you are modifying is the receiver. Hope that makes sense. |
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Oilhead, So yours was just a width of cut problem? Did you have any overlap of barrel ext. ramp issues? Thanks Not the case with mine. Note that the barrel ext. and rec. are nice and even with the mag well cut in the upper i.e. ext. not over protruding into the rec. The Barrel extension feed ramps on my BM barrel hang over the receiver feed ramps. There is just under 1/16" protruding over the rec. ramps. I can see that if a mag does not go up beyond the rec. ramps it (cartridge) could get caught between the two ramps. After looking at some other pics it looks to me that the barrel ext. ramps are different, cut down or may even be a barrel ext. specifically made to be for M4, dont know. |
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Thanks.....Posting pics of my nightmare..Look at the nice little gap to catch the bullet tip. Anyone want to trade a feed ramp flat top for a standard one :) [img]http://www.imagestation.com/picture/sraid105/p83bbeddadec67045236d109f432ab7ca/f971da76.jpg[/img] [img]http://www.imagestation.com/picture/sraid105/pc1943753f00eca62bb0199ddc64d21da/f971da79.jpg[/img] |
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You should never mix a standard barrel with an extended-feedramp upper, as it makes a "shelf" that can catch the tip of the bullet and cause a stoppage. Any other combo is okay, and of course, both parts with extended feedramps is ideal. I would recommend having your barrel (extension) professionally modified to match your upper. -Troy |
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Troy, I looked at the Feed ramp link and or other forums but never read anything regarding any conflict that you just stated. Is a BM M4 profile 16" considered standard? So am i correct that there is a special M4 ramped barrel extension? If so this is something i did not know, and i think this should be listed somewhere to save others from this mess im in. Ive built over a dozen A1/A2's over the last 20 yrs. but this was my first flat top and my first build in 4 years. Naturally i wanted anything new |
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Perhaps my infamous feedramp comparison pic will help: [img]photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=2881[/img] Yes, the barrel extension on an extended-feedramp barrel is different. If you look at the extension on the right, you can barely make out the tip of the "4" stamped at the 3 o'clock position. This is a Colt marking, though, so don't assume you'll see it on other brands. -Troy |
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Yes, it will work identically to a standard (non-extended-feedramp) upper. What you don't want is an indention in the upper receiver that leads to a higher shelf at the edge of a barrel extension (because the barrel extension has standard feedramps). That can potentially "catch" bullet tips. -Troy |
| Thanks again. i seen this pic awhile back. I also looked at it and other pics very close yesterday and thats why i asked the question on the EXT. After reading posts with no mention of this, only persons saying to just take a DREMEL tool to make your own feed ramps. This is why i think this should be public knowledge that you just cant mix the two. So people take note of these threads |
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