Buffer tube fitting issue. (With Pics)

[Slugz]

Finally got the final pieces to finish my first AR15 build and on one of the last few steps of putting it together I am having issues that I hope someone has experience with. Hopefully it's just something I am doing wrong and you guys can enlighten me before I go and remove material to make it fit, lol.

The issue; my buffer tube threads into the lower receiver fine however when it engages the buffer retainer pin it is just barely engaging it in the notch that is in the tube. One more turn and it is too far to engage the notch. This surprisingly isn't the big issue, the weird thing is even backed off to where it will engage even just barely, it sticks out of the lower receiver far enough to stop the upper receiver from mating to the lower receiver.

Being a machinist in the making I was just going to file or grind down the tube and deepen the notch so it fits in tight on the pin and doesn't wobble so much (the rest of my gun fits so perfectly and nothing rattles that the buffer tube looseness drives me nuts), and then my upper would fit badda boom badda bing I'm happy. Can someone tell me what I am missing or is that just what I need to do?

Pics to illustrate;

Thanks in advance to any help and/or suggestions!

 

[Kidd X]

The lower is out of spec. What brand?

 

[Daver_II]

First off.. where is your sling plate and castle nut?

Second, can you back it off one more revolution, and re-take the pictures?

 

[gewehr76]

Please, don't grind anything.
By the looks of it, you screwed buffer tube too far. You also missing a flange and the tightning nut on the butt stock side.
Unscrew the tube from receiver. Install rear receiver flange and nut and then screw the tube just far enough to keep buffer retainer to contact the lip of the tubec and so it won't pop up out of the receiver.
Hope this helps.
G76

 

[Slugz]

First off.. where is your sling plate and castle nut?

Second, can you back it off one more revolution, and re-take the pictures?

Ha ha, oh wow.. I did mention it was my first time, right? Got so excited when I got home and the parts were here I completely missed the plate and nut in the bottom of the box..

With it backed off a turn it does not engage the retainer pin at all, can free turn the tube without the castle nut tightened. The castle nut tightened eliminates any rattle at all which makes me ecstatic. The upper will also fit fine with it backed off one turn, however I would think that the buffer tube is supposed to engage the pin, or else why even have it? Pics following..

 

[Leg]

The pin is to retain the buffer. The receiver extension (buffer tube) is what keeps the pin in place. Everything looks kosher in your last pic. Install the spring and buffer. Does the pin stop them from coming out of the extension? If so all is well.

 

[JuicyFruit]

In one of OP's pics it shows that either the upper or lower receiver is out of spec, there shouldn't be that much visible light between the halves. Regardless of what other parts are exacerbating the issue, the receiver halves aren't kosher.

 

[Kratos]

The pin is to retain the buffer. The receiver extension (buffer tube) is what keeps the pin in place. Everything looks kosher in your last pic. Install the spring and buffer. Does the pin stop them from coming out of the extension? If so all is well.

This is right, your tube won't snug up to the retainer pin, that pin retains the buffer and buffer spring, not the buffer tube. It looks to be held down by the buffer tube in the picture I quoted. The castle nut and end plate retain the buffer tube. Can we see more of the build?

 

[hfx123]

Yep feed spring in and buffer push pin down shove buffer in let pin up... All holds? Tighten nut fire

 

[Leg]

But it is not to spec, the buffer tube should retain the plunger AND engage the pin in order to center the stock and prevent it twisting (even if the castle nut and plate come loose), the extension has a cutout for a reason. In one of OP's pics it shows that either the upper or lower receiver is way out of spec, there shouldn't be that much visible light between the halves. Regardless of what other parts are exacerbating the issue, the receiver halves aren't kosher.

Either the buffer tube isn't to spec, the plunger recess is milled too far forward, or the extension threads in the receiver aren't timed correctly. The buffer tube should be almost perfectly flush with the top edge of the lower when it indexes with the plunger, and should not impede the upper from closing over it. Can OP get away with backing the extension out and living happily ever after? Yes, but it won't change the fact that something is seriously wrong with the dimensions in one or more of those parts.

Seriously wrong? Nothing is wrong.

The retaining nut is what prevents the extension from rotating. That's why it should be staked in place.

If we relied on the pin to keep the tube in place it wouldn't work. First off, the notch in the OPs tube isn't standard and will not be encountered on 99% of the builds out there. Second, assuming the notch was standard, if the tube rotated against the pin than the pin wouldn't spring back in to location and therefore would not retain buffer and spring.

 

[Ruffian]

That is an NEA lower, the gap seen was due to the buffer tube screwed in too far. Push the buffer in so that it is not touching the retaining pin, if it stays held in place by the buffer tube still you are good to go.

 

[Slugz]

You guys are correct. I love you all. It works perfectly and I am just a noob as I suspected. I appreciate all of your patients in not raging at me as you probably wanted to xD

It's an NEA stripped lower with a cheap lower parts kit for now until my wedding is done in a few weeks and I can afford an upgrade. I would like to eventually get into 3 gun one day perhaps and seeing as every part of this rifle I bought on sale I got a great build so far for a great price. The complete upper is a 14.5 inch 5.56 from NEA that they recently had on sale. No optics yet, but as we all know they are expensive and that'll have to wait or the soon to be wife will murder me lol.

I can't say enough good things about the NEA products I have so far. I have another stripped lower and stripped upper and they match and fit perfectly.

Thanks again, guys.

Slugz.

 

[F22_RaptoR]

I'm wondering what kind of receiver extension you're using?

Every single one I've seen looked like this:

With the lower section sticking out more so it doesn't have to be threaded in far enough to interfere with the upper closing. The one in your picture just seems to be flat with a notch cut in.