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Posted: 6/14/2009 5:34:43 PM EST
I'm looking to buy/build a 20" upper for mainly target shooting. I'll be using 68-77 grain target loads mainly, out to 300 yards at best. Some makers (I won't name who so I can stick to the topic) don't offer M4 feedramps with their A3 style (not A4 style) uppers, but they claim not to have any feeding problems with those heavier rounds. I have a Bushmaster A3 upper, originally ripped off of a V-match rifle, and it has never had any failures to feed with heavier rounds.

I guess I'm being anal, but I want to make sure I get a good solid set up, since these damn things cost anywhere between $1200-2000 for the upper alone (not including the scope).

Link Posted: 6/14/2009 6:31:58 PM EST
IMO, no. If you are shooting full auto in a sbr, they may help. In semi-auto it's no big deal. I have them on my new 18" build because they came on the saber bbl. so I got a M-4 cut upper.
Link Posted: 6/14/2009 6:41:40 PM EST
With my long experience with 20" A1, A2, and A2 HBAR barreled rifles, in my opinion M4 feedramps are not really necessary.

Even LaRue Stealth uppers from LaRue all comes without extended feedramps so they probably also don't believe they're necessary.

Link Posted: 6/15/2009 5:14:48 AM EST
No one has shown any real evidence why the M4 feedramps were added, only seen some opinions/sketchy accounts, that it will help in situations of all the most extreme conditions in combination in the M4, i.e. full auto, heavy tipped rounds, worn magazines, Carbine Gas System, bad weather, etc all at the same time.

People have posted again and again they never suffered any problems using the standard feedramps in all sorts of configurations of AR's.

Saw someone speculate the M4 Feedramps could help with larger than 5.56 calipers versions of the AR, that the larger round and its tip would sit a little lower because of its size, don't know how true it is, but if you're dealing with 5.56 it appears they are really unnecessary, especially in a semi-auto AR.
Link Posted: 6/15/2009 9:21:20 AM EST
I don't have any rifles that need M4 ramps to work properly, but I do have a few magazines that need them.
Link Posted: 6/15/2009 3:03:10 PM EST
Mark Westrom of Armalite Inc.determined that extended feed ramps prevented jacket deformation and bullet set back when using the early non-cannellured 77 grain Sierra bullet loads as well as improving feed reliability of all bullet types when firing the rifle on full auto.
Sierra has since developed a heavier jacket cannellured bullet and jacket deformation and bullet set back is not a major issue.

I think if you are using heavier bullets the extended feed ramps do improve feeding.
If you are going to be shooting 55 grain bullets they may not be all that neccessary.
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