Gunsmithing ar15 buffer tube problem

[sixpack340]

i just assembled my first lower. its a spikes tactical. i have an adjustable stock laying around(not sure of the brand) that i was going to use. this stock and buffer tube were used in a spikes lower i had a while back. but for some reason, when i try to thread this buffer tube into my new lower, it is waaayyyy harder than it should be. i damn near need to put it in a vice just to get 2 full turns out of it. its almost like the threads are a different pitch or something. the threads on both parts are fine, no dings or dirt or anything. i thought that all buffer tubes were universal in their thread pitches. what am i doing wrong??

 

[songdogslayer]

Re: ar15 buffer tube problem

There are two types of buffer tubes military spec and commercial

 

[sixpack340]

Re: ar15 buffer tube problem

i thought their was no difference between the mil spec and commercial buffer tubes threads. i thought it was only a difference in length. if they are different, how do i know what i got?

 

[NYShooter]

Re: ar15 buffer tube problem

There is no difference in threads.

 

[dlxcupid]

Re: ar15 buffer tube problem

The threads are the same between commercial and mil-spec.

http://www.ar15fornoobs.com/mil-spec-vs-commercial-spec-buffer-tubes

lol not the best source but it works.

 

[ORD]

Re: ar15 buffer tube problem

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sixpack340</div><div class="ubbcode-body">i just assembled my first lower. its a spikes tactical. i have an adjustable stock laying around(not sure of the brand) that i was going to use. this stock and buffer tube were used in a spikes lower i had a while back. but for some reason, when i try to thread this buffer tube into my new lower, it is waaayyyy harder than it should be. i damn near need to put it in a vice just to get 2 full turns out of it. its almost like the threads are a different pitch or something. the threads on both parts are fine, no dings or dirt or anything. i thought that all buffer tubes were universal in their thread pitches. what am i doing wrong?? </div></div>

When comparing commercial and mil-spec buffer tubes, the threads are identical as others have already said (they are 1-3/16x16 IIRC), but may look different as the mil-spec should have well-defined, almost "sharp" peaks to the threads whereas the commercial tubes often have "flat" or rounded-off peaks. FWIW, Spike's in my experience ONLY uses mil-spec tubes on their complete lowers/rifles unless it is one that you provided them for a build.

Do you have any pics of your lower and the tube in question? (Pics are worth 1k words)...

Without pics of the problem, its hard to tell what exactly is going on. The only thing I can think of off hand is that perhaps you are cross-threading the tube when you try to thread it into the lower????

 

[justpete]

Re: ar15 buffer tube problem

Had the same problem with some Kaiser Defense lowers using LMT tubes. Had to loosen and tighten incrementally using MoS2 anti-seize. Required using a vise per the armorer's manual, and a heavy duty strap wrench. Probably just should've bought the tap Brownells sells and chased the threads. They all went together though but it was a serious pita.

 

[Robe]

Re: ar15 buffer tube problem

I bought the Brownells tap for the threading in lowers and als got the die for the buffer tube threads. Great assets if you do several of these a year. It helps clean up any issue with machining differences like this problem.
I would say you've got one of two problems. Either you have cross threaded these by accident or the threads on your buffer tube are not within specs. I am confident that the Spikes Tactical lower has the proper threading. The best thing to do is try another buffer tube.

 

[sixpack340]

Re: ar15 buffer tube problem

very well. i guess ill try and find a new stock for this thing. i know im not cross threading it. ive tried putting the tube in a hundred times but am just scared to muscle the snot out of it and end up ruining my shiny new lower. thanks for the help gents

 

[Netz]

Re: ar15 buffer tube problem

Lightly and evenly pass a machinist file over the threads of the buffer tube, it might knock the "peaks" down enough to fit into the receiver.
Curt