Feed ramp misalignment

[nightchief]

By "lip" do you mean that the extension in that location protrudes past the M4 feed ramp cut in the upper receiver?

yes...clearly one of the parts is out of spec, but I'm not sure which one yet
NC

[Coal Dragger]

I don't have any tool or anything. No need to eyeball it, just grab a round, a toothpick, or something else that is soft with a sharp point and use it to feel for a step or a lip where the extension feed ramps meet the receiver feed ramps. If everything is in order then the tip of your probe or round will flow smoothly from the upper receiver cuts onto the extension ramps, if it is not in order you'll feel it hang up on the underside of the extension ramp where it protrudes past the ramp cuts on the upper receiver.

[Coal Dragger]

yes...clearly one of the parts is out of spec, but I'm not sure which one yet
NC

You can test on another upper if you want, although given the appearance of the barrel extension not lining up in the upper I'd say it is your barrel extension. Fer-****s-sake the barrel extension has an indexing bolt on the top where it slides into the corresponding slot on the upper, one would think that this bolt would be properly located so the locking recesses and feed ramps on the extension line up on the inside of the receiver.

[GH41]

You think the extension in the part that is out of spec? I can't really tell with the "eye test" myself...

I suppose I can pull the barrel off and try it on another upper

Does anyone have a measurement or spec for the feed ramps of the upper and barrel extension?

NC

Did you buy the barrel from Larue? Looks to me like they sell it both ways. http://www.laruetactical.com/556-stealth-barrel-kit

[nightchief]

Yes, purchased unfired from LaRue in June...I'll contact them in the morning, but I'd sure to have an idea which component is out of spec before I talk with LaRue and Vltor

NC

Did you buy the barrel from Larue? Looks to me like they sell it both ways. http://www.laruetactical.com/556-stealth-barrel-kit

[NickySantoro]

I can't really tell by the pic, but is that a non-M4 cut barrel on an M4 cut upper receiver? That will give you a lip that may well cause hang ups feeding. I converted an older rifle with an A2 upper to a flat top last year and had quite a time finding a non-M4 upper to match. Just a thought.

[nightchief]

No...ordered the LaRue barrel with M4 feed ramps just for this reason. One side lines up perfectly and is nice and smooth, the other side does not. I have contacted both Vltor and LaRue and they are looking over the issue. I'm trying to determine which part is out of spec, or if both are.

NC

I can't really tell by the pic, but is that a non-M4 cut barrel on an M4 cut upper receiver? That will give you a lip that may well cause hang ups feeding. I converted an older rifle with an A2 upper to a flat top last year and had quite a time finding a non-M4 upper to match. Just a thought.

[NickySantoro]

No...ordered the LaRue barrel with M4 feed ramps just for this reason. One side lines up perfectly and is nice and smooth, the other side does not. I have contacted both Vltor and LaRue and they are looking over the issue. I'm trying to determine which part is out of spec, or if both are.

NC

If you can borrow a known good upper and just stuff the barrel in, that would tell the tale. I have a known good non-M4 A2 upper which you can rent for free if you pay postage both ways.

[Digital_Damage]

No...ordered the LaRue barrel with M4 feed ramps just for this reason. One side lines up perfectly and is nice and smooth, the other side does not. I have contacted both Vltor and LaRue and they are looking over the issue. I'm trying to determine which part is out of spec, or if both are.

NC

just based on pictures I would say the barrel extension... it looks really bad.

[nightchief]

Thanks for the offer...I have a Seekins and YHM stripped uppers I can try it on once I fell like taking the upper apart again

NC

If you can borrow a known good upper and just stuff the barrel in, that would tell the tale. I have a known good non-M4 A2 upper which you can rent for free if you pay postage both ways.