AR Sponsor
Posted: 3/19/2008 8:29:59 AM EDT
|
Does anyone know if the Smith & Wesson M&P-15 carbine is mil-spec? The M in "M&P" stands for Military, so I would assume so, but I have to wonder. Thanks. |
Primarily dimensions. Will standard M4 accessories fit it? |
If you're talking about mounting stuff to the rail, then yes, the accessories will fit. The rail system should be a standard 1913 Ricatinny rail. Interestingly enough, the main problem with the 1913 Picatinny rail is that there are very few good go/no go gauges out there, so it will still vary slightly by manufactuer. When I say slightly, I'm talking about 0.01. This might not seem like a lot, but over the length or width of a rail, it can be. For most accessories, the difference will not be noticable EVER. Vertical grips, lights, etc., you won't notice. Some accessories will not lock in 100%. Now the problem could be the accessory or the rail and without a go/no go milling gauge, you'll never know. Hardwarz |
I found out from one of the members here that if the threads on the tube are the same height as the rest of the tube,then it's a commercial tube. If the threads are higher than the rest of the tube,it's mil-spec. |
|
From: en.wikipedia.org/wiki/Picatinny_rail
Hardwarz |
Thank you very much! 
|
|
The answer to your question is no, they are not mil-spec. Only the rifles sold to the military by Colt and FN under the cintract could be mil-spec. The answer to the quetion I think you meant to ask is yes, they are dimensionally the same with regards to accessories and parts compatibility. As mentioned by Hardwarz excelllent post is how to hang thing from it, but also the buffer tube size when choosing stocks between commercial and "mil-spec". Pins and other small parts as well. |
I don't think the wall thickness is different. It's just the stupid way commercial tubes are threaded. The diameter is clearly different but I can't recall off the top of my head why there are [2] sizes. Other than to confuse the masses and require me to spend $40 on a CMT tube so I can run the damn LMT SOPMOD stock. 
|
|
Another way to tell is to look at the back of the tube. If its flat, its likely Mil-Spec, if its slanted, its commercial. Unelss you have an older CMMG. Mine has mil-spec threads, mil-spec diameter, and the slanted back of a commercial tube... I think they now use a 5 pos tube (VLTOR or clone), but I'm not sure. Buffer tubes are weakest at the threads. Just about anything is, just ask my fellow greasemonkeys where bolts break most often... The commercial tubes are threaded with a die, which is why the threads are the pretty much the same diameter as the tube (which on my RRA, is 1.165" for the tube, 1.164" for the threads). Threading the tube with a die removes material. If I'm not mistaken, mil spec tubes have rolled threads rather than cut threads. I'm not sure how it works, but I'm guessing as the point of the threading tool is pressing threads into the tube, that displaced material has to go somehwere, so it gets pushed up. The end result is threads that measure 1.182" on a buffertube that measures 1.148 (on my CMMG). Rolling threads doesn't remove any material from the tube, which is why they are stronger. Someone in the industry could probably explain this a lot better, I know rolled splines are stronger than cut splines and why, and I just tried to apply that to buffer tubes. IOW, I'm talking out of my ass, and hoping I'm right. |
Not better, just different. If you want a SOPMOD, you have to have a mil spec tube. If you want a CTR, you have to order the right model, so I guess you better know which you're buying, right? |
AR Sponsor