There have been several very good articles on the "Milspec" topic written over the years. One of the best I've read is in the current (Sept 2010) issue of Guns & Weapons for Law Enforcement (volume 22 number 6), page 50.
The article was written by Rob Sloyer and he deals with the topic in an easy to understand and concise way... enough technical detail to make the necessary points, but at the same time in easily understood language that even a beginner will understand.
True Milspec is defined by the US Military... there will be a detailed "Milspec" for each and every weapon system purchased by the US Military... in the case of the M4 (and M4A1) it's a Technical Data Package of @ 58 pages (each) and it's proprietary. (The M4 is MIL-C-70599A and M4A1 is MIL-C71186).
Because the Military Specification (Milspec) for these firearms includes select fire (3-shot burst for the M4 and full-auto for the M4A1) none of "us" civilians can own a true Milspec M4... it's as simple as that. In Canada it's a Prohibited Firearm and we can't own it.
But there is much more to Milspec than just that and the above mentioned article does an excellent job of defining how the Milspec applies to 4 main categories when talking about the "AR-pattern carbines"...
- First, is the list of measurements, radii, offsets, and other technical dimensional information
- Second, is the material specifications for the raw material that make up the parts, finishes and surface treatments (for EVERY part in the gun)
- Third, is the assembly methods such as torque values and other criteria for assembly. Every screw and fastener has a specified method of installation
- Fourth, is the testing criteria for parts and assemblies.
There are 2 main reasons (as I see it) that all AR manufacturers don't build their guns to meet the entire Milspec (less the select fire trigger group):
- First is that getting the actual TDP isn't that easy and as said before it's proprietary
- More important is COST... even if a manufacturer has the details of the Milspec or even the majority of it... few manufacturers are willing to spend the money necessary to build the gun to that standard... and few customers are willing to spend the money to buy that standard when they see what it actually costs.
So manufacturers make lots of decisions on what is "important" and where to cut costs so that they can build a good quality product but do so at a cost that the customer is willing to pay. It's a balancing act and every manufacturer makes different choices... and frankly we consumers often have no way to actually get details on what those choices have been.
You don't know if a manufacturer used a softer metal in some of the components in your gun... or if the surface treatment is not as deep as the Milspec calls for... just to mention a couple of areas that are totally hidden.
Even when a company tells you they MP tested their barrel or their bolt... you have no idea what that means because "testing" something only has value when you know what "standard" was used to then accept or reject the tested part... and you don't know. You "assume" that every company that MP tests their barrels does so to the Milspec standards (there is a Milspec standard for everything)... but reality is that commercial companies don't have access to that data and even if they did you are just assuming that a barrel that doesn't "pass" the standard is rejected... but that is NOT the case for many manufacturers. Many people are buying barrels which would not pass the Milspec testing but because the barrel is stamped MP they think it has... think again.
I highly recommend that you read the article mentioned above... this will give you a better understanding of what trade-offs are being made and why some guns cost more than others. You don't need (or necessarily want) a true Milspec gun... a lot of foreign governements as well as the US Military have been quite satisfied buying LMT carbines which DO NOT have front taper pins and are NOT parkerized under the front sight base... but the LMT that you buy commercially is the EXACT same gun (except for select fire trigger group) that is supplied to Military contracts... the same material quality... the same surface treatments... the same assembly protocols... testing protocols... rejection protocols, etc..
Many companies that supply government/MIL contracts actually have two different assembly lines and the product they build/assemble for commercial sale is NOT the same as the product they build for MIL/LE. Don't just assume that the COLT you buy is the same COLT supplied to MIL/LE. Don't just assume that the parts inside that gun are the same parts that are used for the MIL contracts... it's not always the case.
There's a lot more to the "Milspec" topic than meets the eye
Just my 2 cents worth...
Mark