mil-spec vs commercial spec

[kestak]

Greetings,

Can someone explains please?

Can I put a commercial spec tube and stock on a mil-spec lower?
Is it only the tube dimension that is different, or is it the threading diameter?

I have a lower that is mil-spec and I can get a deal on a buttstock that il commercial spec. will it fit?

Thank you

 

[taliv]

you can put either the 'commercial' or 'mil-spec' receiver extensions (aka buffer tubes) on any AR15 lower

the only trick is... after you've done so, the stock that you put over it must be made for that type.

 

[Uncle Mike]

The tubes have the same threads. The difference being the wall thickness of the tubes, commercial tubes are a bit thicker walled than mil-spec tubes and the outside diameter of the tubes are different, the mil-spec tube is smaller in diameter than the commercial tubes.

The radius' are different also, the mil-spec tubes having a smaller tighter radius than the commercial tubes.

The diameter of the two tubes are the deciding factor... you cannot interchange the two, in other words, you cannot put a mil-spec sized stock onto a commercial tube, and vise versa! lol

Check this out...store.magpul.com/downloads/Receiver_Extension_Comparison.pdf

 

[kwelz]

Commercial tubes are bigger but usually also a bit weaker due to the way they are built.

 

[Uncle Mike]

Commercial tubes are bigger but usually also a bit weaker due to the way they are built.

How's that?

 

[taliv]

because commercial tubes are extruded and mil-spec tubes are forged.

check the price difference in mil-spec tubes and commercial tubes.

edit: http://www.brownells.com/.aspx/cid=...bmit=y/Products/All/search=receiver_extension


as usual, there's a good reason mil-spec stuff is more expensive. it's not just tacticool marketing.

(btw, same goes for charging handles)

 

[Ratdog68]

Yes, they fit...

I thought I'd ordered a Mil-Spec stock... but... somehow I ended up with a commercial tubed stock.

I'm in the process of building an AR in 6.8SPC II (6.8x43, but, that's a long story).

If you haven't already purchased your lower receiver, parts kit, stock, etc., give a gander at Surplus Ammo and Arms' offering of the Aero Precision lower. IF you buy the lower/parts kit/stock from them, they'll knock $5 off the price of the lower receiver (which normally sells for $79.99). It's a forged unit. Fine piece... fit/finish are top shelf. Mine went together without a hitch. All that's left is for my upper to arrive from AR15Performance and I'll be ready to dial 'er in. Here's a shot of the lower after assembly.

 

[Uncle Mike]

because commercial tubes are extruded and mil-spec tubes are forged.

This was the norm, not so much nowadays, true mil-spec will always be a turned piece, but the standard for mil-spec now, allows for hydroformed tubes, just like some the commercial one are.

 

[taliv]

you lost me. what's the difference between "true mil-spec" and "the standard for mil-spec now" ?

maybe I'm just dense tonight, but I can't seem to find any mention of hydroforming. you got a link for that?

 

[RockyMtnTactical]

My understanding was the same as yours taliv.

commercial tubes = extruded

milspec tubes = forged

 

[Gary G23]

The biggest difference in tubes is actually in the type of aluminum used. Cheap tubes use 6061. High end tubes use 7075T6.

7075T6 is TWICE as strong as 6061 and the material cost is THREE times that of 6061.

7075T6 is also harder to machine whether it is forged or extruded.