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till44
09-23-2009, 8:55 AM
Anyone ever cut their own M4 feed ramps? I know some will say it is not needed but I have an AR pistol upper that is just not as reliable as I want it to be. Functions perfect with pmags, they seem to put the round up higher in the reciever, but it has problems with other mags or hollow point ammo. You can see the small "lip" where the tips of the rounds catch, so I figure a little work with a round file would fix it. Anyone have any pointers before I start, any tips if you've done your own? Thanks for the advice.

coq
09-23-2009, 9:04 AM
I wouldn't do this. You may end up with a bunch of junk nobody wants. If your barrel has extended feedramps, just get a new upper receiver with cuts and sell your existing one maybe for a slight loss. If neither your barrel or receiver has cuts, swap out the upper in that same fashion.

ar15barrels
09-23-2009, 9:35 AM
I figure a little work with a round file would fix it. Anyone have any pointers before I start, any tips if you've done your own? Thanks for the advice.

A file probably won't cut the barrel extension.
The barrel extension is hardened.

I use a 1/4" diameter stone in a die grinder when I do them.
Work the stone up and down with light pressure.
If you sit in one place, you will just wear away at the stone in one place.
Moving it makes the cut smoother and wears the stone evenly.

Don't deepen the FRONT of the ramp at all.
Only deepen the rear.
Change the angle so that the ramp ends at the exact same point.

There's a 7 degree difference between standard and M4 ramps.

!@#$
09-23-2009, 9:52 AM
i had randal cut m4 ramps in my pistol upper as well. really i had had him chop to 11.5 inches and recrown a super light bushy. then open the gas port and cut M4 ramps.

i did a ton of research about this as i was thinking the softer non anodized aluminum would be damaged over the long term.

what i found was RRA(on all of their uppers for years),CMMG(on their "polished ramps"), and COLT (on many of their left over A2/A4 uppers) did this over the years with no problems. there are some others but these are the ones that stick out in my mind.

this mod is fine IF the ramps are cut right. for the cost a pro charges to cut the ramps VS the cost of a new upper/barrel if you screw up you should just send it out.

till44
09-23-2009, 10:08 AM
A file probably won't cut the barrel extension.
The barrel extension is hardened.

I use a 1/4" diameter stone in a die grinder when I do them.
Work the stone up and down with light pressure.
If you sit in one place, you will just wear away at the stone in one place.
Moving it makes the cut smoother and wears the stone evenly.

Don't deepen the FRONT of the ramp at all.
Only deepen the rear.
Change the angle so that the ramp ends at the exact same point.

There's a 7 degree difference between standard and M4 ramps.

I'll have to look at the upper when I get home again but it I thought it looked like the barrel had M4 feed ramps but the upper hadn't been cut for them. I don't want to touch the barrel, just remove the hard 90 degree angle that sits just before the barrell's feed ramps. It's just aluminum, a file should work fine there right? PM inbound as well.

ar15barrels
09-23-2009, 10:30 AM
it looked like the barrel had M4 feed ramps but the upper hadn't been cut for them. I don't want to touch the barrel, just remove the hard 90 degree angle that sits just before the barrell's feed ramps. It's just aluminum, a file should work fine there right?

A file would do that just fine.

The file you want is the round one for sharpening chainsaw blades.

till44
09-23-2009, 12:02 PM
A file would do that just fine.

The file you want is the round one for sharpening chainsaw blades.

Have a few of those, thanks for the help.

SteveH
10-02-2009, 5:33 PM
Randall,

I have a bushmaster that is giving me failures to feed. It has a non M4 upper and non M4 brl extension. The most common fail to feed is the third round fired from the mag when feeding from the right side of the mag. The bullet tip hits right at the seam between the upper and the Brl extension.

Would adding feedramps to the existing upper and brl likely solve this problem? What does it cost to have this done?

ar15barrels
10-03-2009, 10:05 PM
The bullet tip hits right at the seam between the upper and the Brl extension.

Is there an obvious spot or divot where the bullet tip is catching?