Mil-spec or Commercial buffer tube?

M

Mark_in_MO

New member
Hey guys, I need a little help here please...I have a bushmaster v-match with a fixed stock, and want to go with a adjustable one, been looking at the Magpul STR and ACS-L

Problem is I don't know if I have the Mil-Spec or the commercial tube...Mine measures 1.11 outside diameter if that helps

What all do I need to install either of these two stocks, tools, buffer tubes, springs?

Sorry for the dumb questions but would appreciate a little insight on this project

Thanks, Mark
 
Either. You can purchase the stocks you want in either diameter. Commercial is bigger and has a slanted end. Mil-spec is smaller in diameter and has a flat end. You need the correct spring as the one for the fixed stock may not cycle your bolt properly.
 
The only difference between the MilSpec and Commercial collapsible stock setup is the width of the slot for the "notches". The diameter of the tubes are the same, in fact you can use a commercial stock on a milspec tube, but it will wobble more. Functionally there is no difference between the two.

The differences in the buffer and spring are for Rilfe vs Carbine. Rifle is the fixed stock A2 type, carbine is the collapsible 4 or 6 position. The use different buffers and springs.
 
Since you have a choice, I'd go with milspec since it gives you more stock options.

MIl Spec Hardware Kit $44.95

+

Magpul ACS-L Stock

Or any other Mil Spec diameter stock and you'll be ready to rock.

Originally Posted By: csamThe only difference between the MilSpec and Commercial collapsible stock setup is the width of the slot for the "notches". The diameter of the tubes are the same, in fact you can use a commercial stock on a milspec tube, but it will wobble more. Functionally there is no difference between the two.

No, there are differences.

ctr_stock_specs.jpg
 
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Joebob nailed it. There are differences, and while I've never come across proof of the commercial being weak enough to cause an issue, general consensus is that the mil spec is stronger. Also as Joebob said you have a lot more options on stocks and it is typically easier to find the mil spec stuff. So that's my recommendation, fwiw.
 
I would go with mil spec, that way if you come across an LMT sopmod you'll be ready to go. It's pretty much the best adjustable pos stock I've ever used...
 
Originally Posted By: goose_boyJoebob nailed it. There are differences, and while I've never come across proof of the commercial being weak enough to cause an issue, general consensus is that the mil spec is stronger. Also as Joebob said you have a lot more options on stocks and it is typically easier to find the mil spec stuff. So that's my recommendation, fwiw.

I would think that commercial would be stronger....minutely, as it has a larger tube diameter. Mil-Spec does not mean anything more than it is the spec that the military uses.
 
the only one you need to worry about is polymer lowers they NEED a mill spc tube do to the thread pitch , thread class (sorry) or it will void your lower warrenty and possibly crack it on the reciver extention bore
 
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Originally Posted By: 204farrthe only one you need to worry about is polymer lowers they NEED a mill spc tube do to the thread pitch or it will void your lower warrenty and possibly crack it on the reciver extention bore

The thread is the same regardless of tube type. The way the threads are made are different, and the OD of the tube differ between Commercial and Mil-Spec tubes. However, the threads are the same. The vast majority of polymer lowers come with a COMMERCIAL spec tube, FYI.
 
when you change the major diameter 1.185( mill spc ) to 1.170(commercial) they have same pitch but a diferent class fit . diferent class of fit .015 is like going from 2B class to a 3A class
GIVE ATI a call and talk to them about the OMNI lower don't take my word for it



exampel
External Threads
1A
The loosest fit. Only found on bolts ¼ inch in diameter and larger. Most people will never encounter a fastener with this class of fit. It is mainly used in military hardware where the ability to quickly assemble damaged threads under dirty conditions has the highest priority.

If a class 1B nut with the smallest allowable diameter were fitted to a class 1A bolt with the largest allowable diameter, there would still be a space between them. This is called the “allowance”. Class 1A threads are not coated or plated.

2A
2A/2B is by far the most common class of fit. Like class 1A, class 2A bolts have an allowance. They may be coated.

3A
The closest fit. No allowance. In fact, if the nut's minor diameter was at the minimum permitted, and the bolt's major diameter at the maximum permitted, they would be everywhere in contact, though this situation is highly unlikely.

Class 3A is used for high-strength bolts.
 
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Originally Posted By: doggin coyotesDifferent thread pitch? The things you read on the net. I even read someone say they thought moo-chelle bigbutt-obummer was hot. your are right the thread pitch does not change (TPI) . ment to say class of fit sorry.
 
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SOME poly lowers may be held to different standards or thread tolerances. The New Frontiers, and all others that I've seen, have no issues with Comm or Milspec tubes out of the tens of thousands sold.

ATI may be different, however. ATI lowers have had more issues with fitment and QC than we've seen with the New Frontiers and various brands of uppers.
 
I had ATI one crack and that was the info we got back .I was sent a new one and they did put a warning in with the other new one. Commercial buffer tube only
we have not had a problem after using comm tube
thanks cody and have a nice day
 


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