AR15 stock won't fit?

[sewktbk]

Gents,

just bought a magpul MOE stock from the EE to install on my Bushmaster XM15 in replacement of the factory stock.

I cannot insert the MOE stock onto the buffer tube, the latter is a tiny bit too big for the former. Is this normal? Is it a commercial Vs milspec thing? Or should the MOE stock have come with its dedicated buffer tube?

Thanks in advance,

Cheers

Gaël.

Edit : a bit of research indicates that it is indeed a milspec vs commercial size problem. My question would then be, which one is the milspec, and which one is the commercial, knowing that the MOE stock is smaller/tighter than the tube?

Cheers

 

[TV-PressPass]

Yeah that sounds like you just discovered the difference between commercial and milspec

 

[Ar180shooter]

Easiest way to tell is to look at the buffer tube. If it is flat at the back, it's mil spec. If it has a 5 degree angle, it's commercial. The stock will naturally be the opposite. It sounds like you have a commercial tube and mil spec stock, as afaik the diameter of a commercial buffer tube is slightly larger than that of a milspec tube.

 

[EL34/6L6]

Commercial will fit both tubes, with some wobble on a milspec tube. Milspec will only fit milspec tubes.

 

[Phat Eagle]

Yeah that sounds like you just discovered the difference between commercial and milspec

X3! Back on the EE it goes!

 

[netcon]

.. or just get a mil spec tube to fit new stock

 

[sewktbk]

Thanks a bunch gents. This is my first AR, indeed learning

With the information provided here, I can confirm I have a commercial tube.

Oh well. Anyone wants a milspec MOE stock for 30 bucks + shipping, keep your eye on the EE.

Cheers nutters.

 

[Ebola]

Now that we are on the subject, why do we even have commercial versus mil-spec? It would make sense to have only mil-spec I would think.

 

[tdod101]

Is this why my stocks tend to turn a little bit ? I feel as if the threaded nut is never tight enough and the stock is always moving around a little...

 

[sewktbk]

Now that we are on the subject, why do we even have commercial versus mil-spec? It would make sense to have only mil-spec I would think.

First question that came to mind. I don't get it either.

 

[Hitzy]

Now that we are on the subject, why do we even have commercial versus mil-spec? It would make sense to have only mil-spec I would think.

Commercial is cheaper and easier to manufacture....

 

[Blastattack]

Commercial is cheaper and easier to manufacture....

How do you figure that?

 

[cr5]

Commercial is cheaper and easier to manufacture....

How do you figure that?

Milspec are 7075 compared to 6061 and are manufactured differently. The milspec version is tougher.

http://www.ar15fornoobs.com/mil-spec-vs-commercial-spec-buffer-tubes
http://www.thebangswitch.com/the-infamous-mil-spec-standard/
http://thearguys.com/ar-facts/difference-ar-15-buffer-tubes/

I always buy milspec tubes when building an AR or replacing the buffer tube. Mostly just for parts compatibility across all my AR's but also because most reading says they are slightly better and stronger.

 

[EL34/6L6]

Milspec tube is shorter too, for use while wearing gear and armour.

 

[sewktbk]

Commercial will fit both tubes, with some wobble on a milspec tube. Milspec will only fit milspec tubes.

This brings up a question.

It shows the buffer tube threads as being different for commercial Vs. milspec. Does that mean the female threads on the lower receiver can only accomodate one but not the other?

The 0.015" difference may be slight, but it doesn't take much for threads to be incompatible...

 

[Hitzy]

Both tubes thread on fine....

 

[skoal]

This brings up a question.

It shows the buffer tube threads as being different for commercial Vs. milspec. Does that mean the female threads on the lower receiver can only accomodate one but not the other?

The 0.015" difference may be slight, but it doesn't take much for threads to be incompatible...

Dosnt matter for the threads.

 

[shhh]

This brings up a question.

It shows the buffer tube threads as being different for commercial Vs. milspec. Does that mean the female threads on the lower receiver can only accomodate one but not the other?

The 0.015" difference may be slight, but it doesn't take much for threads to be incompatible...

The crests of the threads are truncated on the commercial tube, therefore not as strong. But the pitch is the same, so either will spin on to the lower receiver. True military tubes are machined to profile from 7075 and have rolled threads. Commercial is cheaper to make because they are made from 6061 extrusions, which has to be a larger diameter to cut (not roll) the threads.

Or so I've read.

Side note for the inexperienced: always grease aluminum threads before assembly. Snug it up dry and you're guaranteed thread damage.

 

[skoal]

Top one is milspec and bottom is commercial.

 

[WRH]

Now that we are on the subject, why do we even have commercial versus mil-spec? It would make sense to have only mil-spec I would think.

It is due to the quality of the aluminum, IIRC. The com-spec is made of a lower grade and needs to be thicker. In order to use the same buffer and spring, the extra material has to go on the outside.