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bubbaskyjacker
05-29-2008, 11:31 AM
i have a spikes lower and plan on getting a cmmg upper, ive read that the mil spec and commercial stocks have different buffertubes or threads ?? what one do i need ?

-hanko
05-29-2008, 11:41 AM
i have a spikes lower and plan on getting a cmmg upper, ive read that the mil spec and commercial stocks have different buffertubes or threads ?? what one do i need ?
Upper has zero to do with it.

Lower buffer tube threads are all the same.

What differes is the diameter of the buffer tube aft of the threaded area. Commercial tubes measure around 1.07" in diameter, mil-spec tubes around 1.04". Functionally, zero issues as long as the big hole in the stock is the same as the diameter of the tube. Since most stocks come with the buffer tube, no worries unless you're getting a new stock to fit an existing tube, or vice versa.

-hanko

bubbaskyjacker
05-29-2008, 11:57 AM
Upper has zero to do with it.

Lower buffer tube threads are all the same.

What differes is the diameter of the buffer tube aft of the threaded area. Commercial tubes measure around 1.07" in diameter, mil-spec tubes around 1.04". Functionally, zero issues as long as the big hole in the stock is the same as the diameter of the tube. Since most stocks come with the buffer tube, no worries unless you're getting a new stock to fit an existing tube, or vice versa.

-hanko

right on!! too simple is the problem

Gryff
05-29-2008, 12:28 PM
Why is there a difference? Does the different sizes provide different capabilities? Otherwise, why was "commercial" even created?

bobfried
05-29-2008, 1:37 PM
Why is there a difference? Does the different sizes provide different capabilities? Otherwise, why was "commercial" even created?

The difference is that it cost almost twice as much to make a mil-spec tube than to make a commercial tube.

Mil-spec tubes have an ACTUAL SPECIFICATION, as in they are machined to a certain diameter and are all the same. So when you buy a stock designed for a mil-spec buffer tube, any stock will work well with any stock that are designed and built to mil-spec. A mil-spec tube is made slightly oversized than machined down to the correct diameter than finished the same way as not to increase the tube diameter.

Commercial tubes are just that, commercial. As in every single manufacturer will make it slightly different as there are no actual specs they have to keep to. They just make, slap a finish on and hope it stays within a prescribed diameter for that specific manufacturer. Commercial tubes can and will have different diameters and wildly different finishes.

the stock bodies are likewise the same, the commercial stock bodies can be made with almost any material in any size the manufacturer wants. Mil-spec stock bodies have to meet certain strength requirements and have their tolerances tweaked much tighter than a commertcial stock. This means that an LMT stock kit will be as tight as you can imagine everytime you buy it versus a commercial setup which could be super tight or super loose. Also, when you put a mil-spec stock on any mil-spec tube it will not rattle much and be reasonably solid versus a commercial which won't even work on a different manufacturer's tube between different makers.

If you don't care and will never buy or swap out your stock bodies than a commercial stock is fine. If you intend to buy a different stock body or simply like the fact that your stock was actually made to a decent standard, read decent, not good, but decent than mil-spec is the way to go. If a mil-spec stock is just barely a decent stock how good do you think a commercial stock at HALF the cost would be?

Ballistic043
05-29-2008, 2:01 PM
but if all mil spec buffer tubes are indeed machined better; can you answer me this..

i just purchased a milspec CTR for my new build from rifle gear and while it fits fine on my stag mil spec tube, it does not fit good on my vltor mil spec tube. it jiggles like a cheap whore. i am not sure if i got a commercial stock; but even if i did, why is there still a noticeable difference between two name-brand milspec tubes?

thats not the first time. my first vltor kit was alot more jiggly than my current vltor rig which is ridiculously rock solid. so either magpul and vltor are making crappy stocks or something else is going on like MY LUCK.

Gryff
05-29-2008, 2:48 PM
Mil-spec tubes have an ACTUAL SPECIFICATION, as in they are machined to a certain diameter and are all the same. So when you buy a stock designed for a mil-spec buffer tube, any stock will work well with any stock that are designed and built to mil-spec. A mil-spec tube is made slightly oversized than machined down to the correct diameter than finished the same way as not to increase the tube diameter.

GREAT info. Thanks!

SS109
05-29-2008, 3:01 PM
http://www.a2host.com/upload/files/buffertubeid.jpg

bobfried
05-29-2008, 3:28 PM
but if all mil spec buffer tubes are indeed machined better; can you answer me this..

i just purchased a milspec CTR for my new build from rifle gear and while it fits fine on my stag mil spec tube, it does not fit good on my vltor mil spec tube. it jiggles like a cheap whore. i am not sure if i got a commercial stock; but even if i did, why is there still a noticeable difference between two name-brand milspec tubes?

thats not the first time. my first vltor kit was alot more jiggly than my current vltor rig which is ridiculously rock solid. so either magpul and vltor are making crappy stocks or something else is going on like MY LUCK.

You sort of answered your own concern in a way. All mi-spec tubes are machined to a certain tolerance, that said if two manufacturer adhere to the opposite ends of the same tolerances than there will be some problem. The specifications are a range of numbers that it has to meet to be called mil-spec.

This is even more prevalent when it comes to the 1913-specs for rails. there's a reason why Larue rules the game. If mil-spec was an exact number that everyone has to meet, cost would be ridicolously prohibited, so rather it's an acceptable range of variance that makes it through. Take 10 mil-spec uppers (wether it be Colt or LMT or anything else mil-spec) made at the exact same time on the exact same line and you will see 10 uppers that are slightly different when it comes to their actual dimensions. But they do all have to fall within a certain range.

But back to the stocks, remember that stock bodies are made from plastic and in the end plastics (polymers) can only be controlled so much in the end product. That said it does still have to adhere within certain specs to be acceptable.

Mil-spec tubes and bodies are just the barely acceptable standards, if you want something better than grab a UBR and see what something built beyond mil-spec feels like. I am always surprised at the amount of people that thinks mil-spec is the best, it is not. Mil-spec is the minimum acceptable standards to create something that will barely do the mission prescribed. If it could be made cheaper and faster and still be barely acceptable it would be. Same goes for uppers, barrels or anything else. Your buying what the military thinks is the least acceptable standard whilst still accomplishing the mission. Those standards are not very high, they're alright in some aspect but they are the minimum. Don't get lulled into thinking because your buying mil-spec that it has to be perfect. All your getting is a promise that it falls within a certain standard that is the minimum acceptable to equip an 18 year old Private in combat. I was once an 18 year old private and I can tell you that the requirements and what is needed for me to perform is not very high.

Look at it this way, if there was already so much variables in mil-spec tubes and bodies, how could anyone justify buying a commercial tube?

To quote the author Scalzi:

"There has never been a military in the entire history of the human race that has gone to war equipped with more than the least that it needs to fight its enemy."

-hanko
05-29-2008, 6:21 PM
SS109, that's what happens when crs strikes...I was low by a tenth of an inch on both tubes:(. I saw that page before, just couldn't find it again...I saved it into my ar folder, thanks for posting it.

-hanko

ar15barrels
05-30-2008, 10:45 PM
Mil-spec tubes are made from forgings or billets.
Commercial tubes are made from extrusions.