AR-15 Feed ramp issue

[WoodyB2]

So went and shot my newly built AR and I was getting a lot of nose dives, the problem occured when using both usgi and pmags. When i got home i noticed that my feed ramps didn't line up all the way. I am new to ARs and decided to post the pics here to see what you guys think.

please forgive the pics, they are not the good and the rifle is really dirty:

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[nick1980]

"nose dives"? do you mean just not getting it to feed right? the ramps don't look bad

 

[WoodyB2]

well it was having a few issues through out the day.

The rounds would not slide up the feed ramps into the chamber, they would just hit the feed ramp and stop. I also think there is an issue with the ejector/ extractor, sometimes it would not extract the round from the chamber or it would not eject and then foul up when loading another round.

Im just worried about the barrel feed ramps sticking out farther then the uppers feed ramps.

 

[nick1980]

who built it? if you was it your first build?

 

[WoodyB2]

The upper is from a friend that purchased it at a gun show...but I pulled it apart when I swapped out the handguard.

 

[sauerwilly]

Looks like you have an M4 feed ramp upper and a "standard" rifle feed ramp barrel. You should have a smooth transition from barrel to extension, no lip.

ETA: any specs on the rifle itself?

 

[JAFO]

The feed ramps won't be causing the problem but exacerbating another.

What is the complete configuration of your rifle? What stock, buffer, etc? What ammo were you using? What were the other symptoms? Did you get any strings of multiple shots off or was there a problem with every one? Is the gas key nice and tight and staked onto the carrier? Is there any uneven wear evident where the carrier enters the receiver extension/buffer tube?

Photos of all of that stuff might help someone notice something out of place.

 

[WoodyB2]

The feed ramps won't be causing the problem but exacerbating another.

What is the complete configuration of your rifle? What stock, buffer, etc? What ammo were you using? What were the other symptoms? Did you get any strings of multiple shots off or was there a problem with every one? Is the gas key nice and tight and staked onto the carrier? Is there any uneven wear evident where the carrier enters the receiver extension/buffer tube?

Photos of all of that stuff might help someone notice something out of place.

I am using the magpul moe rifle stock with a dpms buffer and spring, 80% lower that i milled myself with a dpms fcg installed. I do not know the brands on the barrel/upper/bcg, as i did not assemble it myself. I was using some Independence 5.56, steel case wolf, and some reloaded 223. Both in usgi mags and pmags.

The wolf had a problem every round of not ejecting or feeding.
The independence would foul evey 4-5 rounds. Either a feed issue or an eject issue.
The reloaded 223 would fire around 5-10 rounds and mainly not feed, or would not extract the round from the chamber. thus jamming the next round.


Gas key is staked into the carrier and has no play to it. I dont notice any uneaven wear.

 

[JAFO]

Did the bolt lock open after the last round on any of the attempts?

 

[mcathcart]

Upper receiver A3 or A4? With M4 ramps? - General AR15 Discussion - AR15Armory.com

 

[WoodyB2]

Did the bolt lock open after the last round on any of the attempts?

Yes, locked open every time with empty mag.

 

[JAFO]

Well I don't know much (I should have added this disclaimer before I said anything) so I don't know what the problem is but... do leave the Wolf at home and probably the reloads too until you get it figured out. Wolf usually isn't as hot as most factory ammo so it makes sense that it showed the worst results.

One thing you might try is seeing if your buddy has a different carbine spring and a different carbine buffer or two to try out. If you have a standard weight carbine buffer try a heavy buffer perhaps (or vice versa). The feed ramps can be addressed after you figure out the other problems. The lower isn't likely a problem unless the receiver extension hole is off center or not parallel with the axis of the bore. If that was the case though you'd likely see some scarring/galling on the tube itself.

Was the upper new or used? If used did you take the gas block/front sight base off when you changed the handuard out? Did you clean out the gas tube? Did you mark the barrel and/or gas block to make sure the gas ports in the barrel were aligned when you re-installed it (if you did remove it)?

Oh, and how does the fired brass look?

Pictures of all of this might help someone who does know what they are talking about help you figure it out.

 

[madcratebuilder]

Independence 5.56, steel case wolf, and some reloaded 223. Both in usgi mags and pmags.

I suspect ammo related. Get some M193 NATO, that's what the AR is designed to use. Get it sorted out with good ammo, run several hundred rounds THEN start trying steel case ammo. Steel case MAY need a upgraded extractor and spring/O-ring.

 

[HahnsXD]

I was shooting with him yesterday. His rifle seems to be getting plenty of gas (more than mine), brass deflects forward on his rifle, mine doesn't hardly hit the deflector and ejects to the rear. He tried my BCG, same problem. He tried my mags, same problems. I ran his ammo in his mags in my rifle and had no problems. The "reloaded ammo" is BVAC factory reloads and runs fine in my gun, we split the same 1000rd case.

He seems to be having a couple issues, brass not being extracted properly, another round is stripped and then empty brass is rammed into the top of the barrel extension. And the second would be "nose dives", the round plows straight into the feed ramp (in the upper, not barrel extension) and stops.

Could too much gas be causing extraction problems?

 

[JAFO]

What happened when you tried his upper on your lower?

Did you check headspace?

Is the barrel extension flush with the face of the upper inside (should be set forward less than .012")?

What are the barrel markings? Is this a .223 chamber possibly? Have you checked the chamber and spent brass for imperfections?

Carefully inspect the spent brass for signs of overpressure?

Overfunction can cause failure to extract but is it too much gas or too much pressure?

Like I said before, photos of everything might help people who know what they are looking at notice something that might be causing problems.

 

[SCARed]

The wolf had a problem every round of not ejecting or feeding.
The independence would foul evey 4-5 rounds. Either a feed issue or an eject issue.
The reloaded 223 would fire around 5-10 rounds and mainly not feed, or would not extract the round from the chamber. thus jamming the next round.


Gas key is staked into the carrier and has no play to it. I dont notice any uneaven wear.

Based on this, it's sounds like your BCG doesn't have enough force to cycle properly. Also in the 2 photos, the upper seems pretty dry. I'd lube up the upper and the BCG quite a bit more and see if that helps.
You might also check your gas block. If it's loose you might be getting inconsistant gas flow.

 

[WoodyB2]

I checked the gas block and noticed a lot of soot on the barrel and on the gas tube where it enters the block, also is was ever so slightly canted to the driver side. I went a head and ordered a new block and tube just to make sure. I also added an o-ring to the extractor to see if that helps.


We did not try different lowers while shooting, looking back now that one of the things we should have tried.

 

[JAFO]

You should be able to figure it out without putting money into it. It's hard to diagnose over the internet though.

 

[mjbskwim]

I think the ramps aren't perfect ,looking at the pictures but it sounds like your gas block is not on correctly also. Not getting enough gas down the tube.

What I do is put the little red tube on the cleaner in the gas tube at the chamber,spray it good. The barrel should be full of cleaner or you didn't quite line the block up.

And use some good ammo while you're testing...if you can find some.

And make sure the gas rings on the bolt aren't lined up!

 

[WoodyB2]

Ok I fixed my problems. First off I put an o-ring in the extractor. Then with some help from Hahn we figured out that when I changed out the barrel nut for my new hand guard I installed the gas block to far back, I was un-aware that I needed a gap between the block and the lip of the barrel . It was entirely my failure in research before I swapped it out.

So I put the gas block and tube on correctly and with the extractor o-ring I am back to having a perfect running ar.

here are some pictures of the gap im talking about.

no gap (old block and tube):


new block, and the correctly installed (sorry, didnt want to take the guard off again):


bonus shot of my rifle: