Buffer tube question

[EWB_TUS]

I built an LR308 rifle initially with a carbine configuration and am trying to switch it to the rifle configuration. I bought an AR-Stoner rifle buffer tube but it doesn't thread far enough into the upper to retain the buffer retaining pin. I included a picture. Is there a rifle length buffer tube that will thread farther into the upper. Had no issue with the carbine one but it has many more threads and a castle nut.

Thx

[EWB_TUS]

PS - meant lower, that's where the buffer tube threads in as I am sure the rest of you know 🙂.

[shooterrex]

I've always had good results with parts from these people. 

AR-15 / LR-308 A2 Standard Rifle Buffer Tube https://share.google/Rk76dW7phgeT3CV3Z

[EWB_TUS]

Thanks for the link; he was very helpful. Apparently, I don't have a "mil spec" receiver. At this point I am thinking I have to mill off the shoulder of the buffer tube so it will thread in far enough and either drill and tap a pin to hold the buffer tube in the right position or use blue threadlocker to hold the buffer tube in the right position. Obviously, thread locker would be easiest but is it sufficient?

Thoughts?

EWB 

[shooterrex]

Rockset is a thread locker that only comes off if you soak it in  water.

If the gun runs with the carbine extension Magpul makes rifle stocks that work on carbine extensions.

If a milspec carbine extension works and holds the buffer retainer in I find it hard to believe the lower is out of spec.

I have bought parts from those people but never called them and ask for advice.

Take some measurements and post the pics of them.

[EWB_TUS]

In communicating with Kurt at Kak Industry, he indicated that the rifle buffer tube I have is correct but that the buffer retaining pin location in my receiver is not. The carbine buffer tube works because it has more threads than the rifle buffer tube and is set with the castle nut. The rifle buffer tube has a shoulder that prevents it from going any deeper into the receiver. Thank you for the information about Rockset. Never heard about it before.

[Albroswift]

Problem I see just looking at the photo is the rifle extension is threaded in about the right amount. If you threaded it in far enough to catch the keeper (Incorrectly located), it would interfere with the upper when closing. Most carbine extensions I am familiar with have extra meat down where it contacts the buffer retainer. If you thread in the rifle extension far enough to retain the pin  you may have to file some off the top to fit it . 

 

Edited June 18 by Albroswift

[98Z5V]

Rifle receiver extensions thread directly into the lower receiver.  You're using a carbine endplate, then the rifle receiver extension - I can see it.  Get rid of it.

 

[Albroswift]

I see what you are looking at, but if it's a carbine endplate where does the tab go?

[EWB_TUS]

What looks like a carbine end plate is actually a beveled part of the lower receiver. I thought about milling that off but then I have to take the whole lower apart, get it milled, repainted, etc.

[shooterrex]

This stock will work w/a carbine extension. 

PRS Lite Stock https://magpul.com/prs-lite-stock.html?mp_global_color=118

[Albroswift]

if you milled off the back the  rifle tube would stick out the front. I'd go back to your carbine extension, if it runs don't fuk with it. Find a stock you like that fits the carbine extension there are plenty! If you want a rifle build one you already have a good start with an extension, we have started with less.  Welcome to the forum!!!

Edited June 19 by Albroswift

[98Z5V]

On 6/15/2026 at 8:35 AM, EWB_TUS said:

I built an LR308 rifle initially with a carbine configuration and am trying to switch it to the rifle configuration. I bought an AR-Stoner rifle buffer tube but it doesn't thread far enough into the upper to retain the buffer retaining pin. I included a picture. Is there a rifle length buffer tube that will thread farther into the upper. Had no issue with the carbine one but it has many more threads and a castle nut.

Who is the manufacturer of this lower receiver?  From the shelf I'm looking at, it looks like old-skool original DPMS.