Feed ramp misaligned?

[Dildobaggins]

So I'm doing a SHTF build, and got my criterion core barrel and aero upper today. I put them together without a barrel nut for shits and giggles, and I noticed this. I've built like 10 ars and I honestly don't think I ever checked this, or maybe I did and wasen't worried about it. Is this normal or is something out of spec on the barrel or upper receiver? It might be hard to see, but on the right side of the feed ramp/barrel extension it doesn't appear to be perfectly aligned. Thanks!

 

[wade2big]

I don’t see what you do. Seems fine. Did you cycle ammo through it?

 

[Dildobaggins]

I don’t see what you do. Seems fine. Did you cycle ammo through it?

I haven't. I just have the barrel and the upper receiver. I just checked my WOA barrel and reciever. And that's worse than that. Maybe I'm being too anal about it. If you look very closely on the right side, the barrel extension hangs over the feed ramp by maybe a millimeter...as I type this out I realize this is probably incredibly stupid and it's fine. . Just checking with the experts.

 

[wade2big]

I haven't. I just have the barrel and the upper receiver. I just checked my WOA barrel and reciever. And that's worse than that. Maybe I'm being too anal about it. If you look very closely on the right side, the barrel extension hangs over the feed ramp by maybe a millimeter...as I type this out I realize this is probably incredibly stupid and it's fine. . Just checking with the experts.

An expert didn’t answer your question. I did. Either way it should be just fine. For the slim chance it isn’t, its nothing a marker and a few swipes with a file wouldn’t fix.

 

[bill_van]

Once you have it built, take a look at the brass (hand fed) and see if there are scratches that match the extension. It is probably okay and won't pose any issue.... the important aspect of the ramps is that they "feed". Extraction and ejection should be fine. If the scratches are deep, as stated, a file or dremel with a fine stone will fix it right up. Just go slow and take a little at a time if you have to.

 

[Constructor]

You can always blend the ramps using a 3/16" chainsaw sharpening stone in a dremel tool.

 

[Dildobaggins]

So I had another aero upper receiver, and put the barrel into it, and it lined up perfect, and while I was doing that I noticed the barrel had a way tighter fit in the upper, than the aero upper I just bought. Put the barrel back on the new one, and it's really loose, so I think something is out of spec with the reciever. Asked for an RMA from primary arms this morning. Haven't heard anything back yet. I've bought alot of stuff from them, but never had to return anything. Hopefully they are good about it.

 

[bill_van]

Sometimes they are a little slow but they usually take care of business in a reasonable time. Was that one of the uppers they recently had on sale?

 

[Dildobaggins]

Sometimes they are a little slow but they usually take care of business in a reasonable time. Was that one of the uppers they recently had on sale?

Good to hear. Yep it was. Maybe it's just me, but I feel like they have been having sales like crazy lately? I also got aero M5 lowers for $119 and aero gen 2 lowers for $73. The lower I got with this upper, could have passed as a blem, It had some digs and Nick's in it too.

 

[Obi-WanKannoli]

Is there any little bit of rotational play when the barrel is seated and no barrel nut is on? Sometimes Pins can sit a little loose in the receiver and will cause the barrel to cant during installation.

Alignment of these components is something to consider. Misaligned feed ramps and barrel extension means a canted gas block means a gas tube on an angle inside the receiver. Your bolt lugs will not index perfectly with the barrel extension lugs and have "more than intended" contact with them at the speed of the bolt cycling, same with your gas key into your gas tube. It's a good way to chew up bolts, peen barrel extensions, bend gas tubes, etc. Could possibly induce some cycling and function issues too.

A good function test is to install your bcg with out the bolt, with the charging handle. Hold the gun level and push the carrier in out, see how much resistance there is at the carrier. Do it again with the bolt and see how much resistance there is at the extension with the bolt.

A proper setup should really glide right until you are getting to the point where the bolt is cycling within the bcg and you have the resistance from the gas rings.

This doesn't mean your parts are throw aways, it is possible with patience to torque the barrel nut and maintain alignment. I have had to do it before myself. If you can return the upper I would just save yourself the headache and do so.

 

[Dildobaggins]

Great info man. Thanks alot! I'd say zero rotational play, and pin is solid. Did what you said with the BCG with and without the bolt. It slid right in. Could not tell the difference between the the BCG with the bolt and without. However, sliding the bolt on the way out, I did experience some resistance. The bolt was almost all the way out of the barrel extension. Feels like it's hung up on something. Not sure what that is, but I don't think it's the extension? I did have the upper upside down, because I wanted to see what was going on inside and it provided a level surface. Thanks for the info. Hopefully I won't need it in the future. Waiting on an RMA from primary arms. The barrel is very loose in the upper as well. But not it any other upper I have.

 

[S197]

So I'm doing a SHTF build, and got my criterion core barrel and aero upper today. I put them together without a barrel nut for shits and giggles, and I noticed this. I've built like 10 ars and I honestly don't think I ever checked this, or maybe I did and wasen't worried about it. Is this normal or is something out of spec on the barrel or upper receiver? It might be hard to see, but on the right side of the feed ramp/barrel extension it doesn't appear to be perfectly aligned. Thanks!

This is common and your set up are good to go.

 

[Dildobaggins]

This is common and your set up are good to go.

Thanks! I figured I would be. I'm usually not like this at all. I just figured if I'm doing a SHTF gun, I want to be 100 percentage confident in the build itself.

 

[S197]

So I had another aero upper receiver, and put the barrel into it, and it lined up perfect, and while I was doing that I noticed the barrel had a way tighter fit in the upper, than the aero upper I just bought. Put the barrel back on the new one, and it's really loose, so I think something is out of spec with the reciever. Asked for an RMA from primary arms this morning. Haven't heard anything back yet. I've bought alot of stuff from them, but never had to return anything. Hopefully they are good about it.

More then likely the upper is still in spec. But this where buying higher end uppers like LMT shine, as they tend to stick with a tighter tolerance vs aero.

 

[S197]

Thanks! I figured I would be. I'm usually not like this at all. I just figured if I'm doing a SHTF gun, I want to be 100 percentage confident in the build itself.

if you want to be 100%, send the barrel and upper off to someone like Adco and they can polish/ blend the ramps. Most people mess up the ramps when they start removing metal.

 

[Obi-WanKannoli]

Great info man. Thanks alot! I'd say zero rotational play, and pin is solid. Did what you said with the BCG with and without the bolt. It slid right in. Could not tell the difference between the the BCG with the bolt and without. However, sliding the bolt on the way out, I did experience some resistance. The bolt was almost all the way out of the barrel extension. Feels like it's hung up on something. Not sure what that is, but I don't think it's the extension? I did have the upper upside down, because I wanted to see what was going on inside and it provided a level surface. Thanks for the info. Hopefully I won't need it in the future. Waiting on an RMA from primary arms. The barrel is very loose in the upper as well. But not it any other upper I have.

Yeah no problem! Good, definitely just swap it out and avoid the head ache if you can. If you felt some resistance on the way out that is likely the back of the bolt lugs getting hung up on the on the inside of the lugs in the extension. Chamfers on these parts are, often times, only on the front of the barrel extension where the bolt interfaces. For bolts same but opposite. Generally chamfered edges on the front of the bolt lugs, squared on the back in a lot of instances. So if you think about it, with misalignment you likely have on one side of the lugs two square edges locking up during election. This failure will absolutely cause FTE in undergassed guns or guns using weak ammunition. It's all good stuff to know about anyway I guess!

 

[acudaowner]

looks good to me .

 

[308pirate]

as I type this out I realize this is probably incredibly stupid and it's fine.

Your realization is correct