by Tiger McKee Just because chicken meat is white doesn't mean it's actually white meat from the chicken, regardless of what the commercials say. The same thing is true when it comes to "mil-spec," or military specification, a term that is tossed around very casually these days. While a lot of parts are advertised as being mil-spec, in truth very few of them are. This fact was really driven home this last week when I was assembling an AR carbine. I installed the bolt catch in the receiver, and when I checked it noticed the catch would not pop up high enough to trap the bolt. It was physically binding. I took everything apart, and started with another catch, using the same spring and plunger. Same problem. I disassembled it, did a little polishing on the catch, and installed it without the spring and plunger and it worked fine. Drove the pin out. Put it all back together. Still had a problem. I had already checked the holes in the receiver, so I knew that was good. It comes apart again, and I used another plunger, even though I had compared the ones I had and they all checked out the same. Again, not working right. I tore it down and pulled another spring out of my parts stash. Still, no luck. I had finally gotten to the point of really being frustrated and decided to compare and check each part against what I knew were Colt factory parts. The spring was out of spec. I'm not sure where the problem bolt-catch spring came from. I had several in stock, some "mil-spec" and some from Colt. The problem spring was shorter than the Colt spring, which is about all I can tell you other than it would not work. After assembling everything one more time with the Colt spring it worked fine. That one small spring had cost me about an hour of head scratching. There is a greater difference when you start talking about parts like the bolt and barrel. For example on a Colt rifle the bolt and barrel are "high-pressure proof tested" - firing a proof round that is twenty percent hotter than a normal round - and runs through a magnetic particle inspection, which will discover any imperfections. There are over 100 additional different points of inspection that every rifle goes through. Each spring, detent, and every other part is inspected, and must be interchangeable with any other part from any other rifle. The point is that not all parts that are advertised as mil-spec meet the true definition of that term. Just because its dimensions are correct doesn't mean it's made from the proper material, or properly hardened. This more true now than ever before. With the rise in demand for AR parts new companies have popped up and are dumping AR components out the door as fast as possible. Some of these companies are producing well-made parts. Some of them are producing explosions waiting to happen. When it comes to parts, "parts ain't parts." Any part used in a weapon that may be used to fight with had better be up to the task. A breakage on the range isn't a big deal; most likely someone will have the part you need in their kit bag. A breakage in a fight can mean disaster. Tiger McKee is director of Shootrite Firearms Academy, located in northern Alabama. He is the author of "The Book of Two Guns," writes for several firearms/tactical publications, and is featured on GunTalk's DVD, "Fighting With The 1911 - http://shootrite.org/dvd/dvd.html Website: www.shootrite.org http://www.facebook.com/pages/Shootrite-Firearms-Academy/156608611038230?ref=ts