What is MilSpec - and should I care...

KevinB

KevinB

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Okay this thread is going to get long.

I was asked by a few posters to offer my thoughts here.

MilSpec is just what it means - something that meets the Military Specification for a part or component.

For many things this is used based off the M16/M4 TDP (Technical Data Package).

I am going to start on Commercial Versus MilSpec Buffer tubes - as this is one that is thrown out a lot.

The key to note here is that MilSpec has a specification, this refers to manufacturer process, materials, dimension etc.

A MilSpec buffer tube is.
Aluminum Alloy 7075 T6 material that is impact extruded.
It is blasted and Hard Coat Anodized per Mil-A-8625 (another MilSpec) (HCA III Class2) Dyed and Sealed (once again color and type per Spec).
It is then Dry Film lubed.

There is more - but the idea here is to show (but not totally explain how) that a MilSpec tube has a specific spec.

Some Commercial tubes are thru extrusions that then have a cap that is either welded (and 7075 does not weld nicely) or threaded and fixed (usually with some sort of loctite - or not). Commercial tubes can be of varying diameters (curse you floppy buttstock), and can be of differing materials, coating and the rest.

This is not to say you could not make a commercial buttstock that is not a better product than a MilSpec one, however the MilSpec buttstock will at least function safely in the firearm. If you getting a non MilSpec part especially one that en-captures moving high velocity parts.

I will go more into barrel steel etc later or tomorrow (date night tonight at the KevinB household).
 
KevinB said:
...I will go more into barrel steel etc later or tomorrow (date night tonight at the KevinB household).
Click to expand...

What, Mrs. B doesn't get turned on by talking barrel steel specs? I guess the rest if us here are just weird.

Thanks for the details and the ones to come. This is good info and I could see this becoming a sticky....wait a minute...date night....bow-chica-bow-bow ;)
 
Appreciate you taking the time to explain that, better than chucking stones at us because no one ever explained it to us before!
 
Some Commercial tubes are thru extrusions that then have a cap that is either welded (and 7075 does not weld nicely) or threaded and fixed
Click to expand...

Could you name any manufactures in particular that have used the welded method? No one seems to actually be able to show me the existence of such an animal. Do you know of any manufacturers that currently use this method? Welded aluminum sticks out like a sore thumb when anodized, so it would be obvious.
 
I have found with buffer tubes there is a difference between a MilSpec buffer tube and a buffer tube that fits milspec stocks. The latter being a “commercial tube” that is made to the milspec diameter.

I look forward to the rest of your write up...
 
From what I've read the MilSpec Buffer has an outside diameter of 1.14 inch while a commercial is typically around 1.17 inch which would be why a commercial spec stock is floppy when put on a MilSpec tube. I seem to remember also reading one being slightly longer than the other as well but can't remember which.

I am curious to know if buffers and springs are can be interchanged between the two receiver tubes and if the inner diameter is different.
I have 3 tubes and 1 is MilSpec and the others are commercial. Can I swap buffers and springs back and forth without issue? I keep forgetting to pull them apart and measure them when I'm playing in the gun room.
My plan is to just replace the commercial tubes with MilSpec so I can standardize parts compatibility. I just sold one of my AR's so I will only need to replace one tube and I want a different stock on that AR anyway.
 
cr5 said:
From what I've read the MilSpec Buffer has an outside diameter of 1.14 inch while a commercial is typically around 1.17 inch which would be why a commercial spec stock is floppy when put on a MilSpec tube. I seem to remember also reading one being slightly longer than the other as well but can't remember which.

I am curious to know if buffers and springs are can be interchanged between the two receiver tubes and if the inner diameter is different.
I have 3 tubes and 1 is MilSpec and the others are commercial. Can I swap buffers and springs back and forth without issue? I keep forgetting to pull them apart and measure them when I'm playing in the gun room.
My plan is to just replace the commercial tubes with MilSpec so I can standardize parts compatibility. I just sold one of my AR's so I will only need to replace one tube and I want a different stock on that AR anyway.
Click to expand...

The commercial have slant ends whereas the MilSpecs are flat, but can't recall if the OL's are the same or not. The inner diametre are the same, that I recall. The thread pattern is slightly different between the two as well.
 
BenL said:
The commercial have slant ends whereas the MilSpecs are flat, but can't recall if the OL's are the same or not. The inner diametre are the same, that I recall. The thread pattern is slightly different between the two as well.
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Are you on glue? Just think about that for a second.

Not all commercial tubes are slanted on the end either. Carbines did exist prior to the slanted M4 style buttstocks being introduced around 2002.

Mirk brings up a good point. Just because a tube is mil-spec diameter doesn't mean that it meets the rest of the specs laid out in the TDP.
 
Good breif description, I wish however there was only ONE spec, that would save getting the wrong part sometimes, as many do not check the OD of their tubes etc it seems? :)
 
Leg said:
Are you on glue? Just think about that for a second.
Click to expand...

Either tube will thread into any AR receiver, but the threaded portion of a commercial tube is smaller in diameter than that of a Mil-Spec tube. This means that the threads on the commercial tube do not fully engage those of the receiver, as they are shallower.
 
tjhaile said:
Either tube will thread into any AR receiver, but the threaded portion of a commercial tube is smaller in diameter than that of a Mil-Spec tube. This means that the threads on the commercial tube do not fully engage those of the receiver, as they are shallower.
Click to expand...

This applies to ALL non-milspec tubes? Comspec tubes are threaded to a different
specification?
 
Either tube will thread into any AR receiver, but the threaded portion of a commercial tube is smaller in diameter than that of a Mil-Spec tube. This means that the threads on the commercial tube do not fully engage those of the receiver, as they are shallower.
Click to expand...

OK, I don't understand why the commercial tubes would have to be smaller OD. If the threads don't fully meet, what is the point of making a tube like that? Also, what is the reason for the slanted end on the commercial tube? Is it related to the extrusion process?

From what I understand, the mil-spec tubes are forged and bored as opposed to the commercial extrusions. However, some mil-spec tubes, such as made by VLTOR, are also extruded, so even though they have the proper OD, they are also not as strong as the forged tubes.
 
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