I just received a complete upper from PSA (one of their $400 complete specials) and I came to the conclusions that the receiver has M4 feed ramp cuts but the barrel extension has standard cuts. Basically it looks like the example in the lower left corner of this picture:

Click image for larger version.  Name: feedramps2.jpg  Views: 107  Size: 123.6 KB  ID: 36749

As the picture denotes, this is apparently "Bad". I understand this can lead to feed issues. Since the upper was advertised simply as having "M4 Feedramps" I feel like the upper was not as advertised. I have contacted PSA to see what they have to say, and this isn't an attempt to throw them under the bus (yet) but I wanted to ask:


  1. Is the potential for feed issues as worriesome as it sounds? I haven't shot the upper yet to know if it displays any problems, but since this is a brand-new upper, I don't want to just leave it as is if this is truly a condition to remedy.
  2. Second, and this is probably debatable, would one assume an complete upper that is advertised as having "M4 Feedramps" is going to have the M4 cuts in BOTH the upper receiver and the barrel extension, or is that an inherently flawed assumption?
  3. Last, I have run across reports of guys and shops using a Dremel to remedy the ramp issue. Has anyone here done it themselves or recommend somewhere that would do it in case I am unable to get a satisfactory remedy from the seller?


Thanks for having a look! Oh, and if anyone can tell me how to make my images appear larger than a postage stamp, please let me know!