Are the threads different or can you put a Mill Spec tube on a Dpms 308 that has a Commercial tube on it now
- Thread starter Trihawkcal
- Start date
Sort of. The threads will fit into the same receiver, so you can put either a Mil-spec tube or a commercial spec tube into the same lower, no problem.
However, the threads are deeper on a mil-spec tube than on a commercial spec tube, which gives some additional strength at that threaded point once assembled over the commercial tube.
Additionally, the tube diameter where the stock slides over the tube is larger on the commercial than the mil-spec. So you should stick with the correct size stock for your tube, or it will be loose or won't fit at all, depending on direction. This was traditionally done because comm spec tubes were originally lower quality metal (and sometimes still are) than the mil spec. Though these days you *can* find comm spec tubes made with good quality metal, but not all are.
FROM LMT:
However, the threads are deeper on a mil-spec tube than on a commercial spec tube, which gives some additional strength at that threaded point once assembled over the commercial tube.
Additionally, the tube diameter where the stock slides over the tube is larger on the commercial than the mil-spec. So you should stick with the correct size stock for your tube, or it will be loose or won't fit at all, depending on direction. This was traditionally done because comm spec tubes were originally lower quality metal (and sometimes still are) than the mil spec. Though these days you *can* find comm spec tubes made with good quality metal, but not all are.
FROM LMT:
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There are even "milspec" commercial tubes. Meaning they are made like commercial tubes but to milspec ratios.
One way to tell by looking is that the commercial, regardless of dimensions or ratios, won't have cut threads and the minor imperfections a cutting tool leaves when it turns down that tube on a lathe like an LMT tube has.
Commercial tubes generally aren't designed to handle the abuse the milspec one will either, aren't they extruded? but the level of abuse is widely variable. I'd say unless you IMT with your weapon, a commercial tube will likely do you about as well as any other I'd imagine, meaning they'll all take a little hit and any recoil you throw at 'em. Provided you had the proper buttstock to latch onto it of course.
And yeah, those cut threads do fit the lower better than the other method.
One way to tell by looking is that the commercial, regardless of dimensions or ratios, won't have cut threads and the minor imperfections a cutting tool leaves when it turns down that tube on a lathe like an LMT tube has.
Commercial tubes generally aren't designed to handle the abuse the milspec one will either, aren't they extruded? but the level of abuse is widely variable. I'd say unless you IMT with your weapon, a commercial tube will likely do you about as well as any other I'd imagine, meaning they'll all take a little hit and any recoil you throw at 'em. Provided you had the proper buttstock to latch onto it of course.
And yeah, those cut threads do fit the lower better than the other method.
The difference in thread cutting is:
On the milspec, the entire tube is solid aluminum, and the thread recesses and entire tube are cut downward. Leaving the peaks of the thread sticking up above the body of the tube. The entire tube was once the diameter of the peaks of the thread.
On the Comm spec, the tube is manufactured slightly larger, and the threads are cut into the tube, but at a shallower thread depth. The tube is always the same diameter, and the threads cut into the tube. The pic I posted (and then reposted after the link died) shows this well. See the threads sticking up over the tube diameter on the milspec, but cut into the diameter on the comm spec? I have heard reports where the threads on a comm spec tube were part of the form, and not actually cut into the metal, but I haven't personally verified this or seen one where this was apparent.
On the milspec, the entire tube is solid aluminum, and the thread recesses and entire tube are cut downward. Leaving the peaks of the thread sticking up above the body of the tube. The entire tube was once the diameter of the peaks of the thread.
On the Comm spec, the tube is manufactured slightly larger, and the threads are cut into the tube, but at a shallower thread depth. The tube is always the same diameter, and the threads cut into the tube. The pic I posted (and then reposted after the link died) shows this well. See the threads sticking up over the tube diameter on the milspec, but cut into the diameter on the comm spec? I have heard reports where the threads on a comm spec tube were part of the form, and not actually cut into the metal, but I haven't personally verified this or seen one where this was apparent.
If you're going to change to a mil-spec tube I highly recommend the BCM. I have slammed the snot out of a few of mine and they haven't flinched. I have bent a couple of commercial tubes over the years. If it's just for range use, commercial will be fine.
The person who invented the commercial tube, should be taken outside and crucified.
That being said, tubes are tubes. Any Mil spec tube you find in stock should work. They are all most likley made on the same machines anyway.
That being said, tubes are tubes. Any Mil spec tube you find in stock should work. They are all most likley made on the same machines anyway.
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