Does anyone have a M&P 15 Sport II handy that you could quickly measure the dimensions of the buffer tube and let me know? I am specifically interested in whether or not it measures between 1.16 and 1.18.

Long story as to why, but the short of it is, I do not have a 15 Sport II to measure myself, or I would've done it. Thanks in advance for any help anyone can offer!

It is mil-spec dimensions.

Mil-spec appears to be 1.148 based on what I found online. I was really hoping it would be between 1.16-1.18.

Can we ask why? You have my curiosity now. 1.148 and 1.16 are pretty close.

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Still carrying my S&W 642

I'm betting he has a commercial spec stock that he wanted to put on a Sport when he gets it.

I think you are right, commercial tube diameter is 1.168 (from what I read) so that's what he is probably looking at.

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Still carrying my S&W 642

The reason why is I live in a restricted state and putting a Thordsen stock on is one of the only ways that we can get an AR. I'd rather have a Thordsen with a drop free mag than a pinned-mag "full feature" carbine that I have to break open to load each time. Just trying to do my homework on the M&P 15 Sport II before I possibly purchase one along with a Thordsen.

Anyone out there have a M&P15 Sport II and have any feedback? Good entry-level AR? I've narrowed it down between the 15 Sport II and the Ruger AR-556.

Doesn't the FRS-15 stock extend from where the pistol grip normally is, not the buffer tube? If so why would the buffer tube diameter make a difference?

As for the Sport 2 being a good entry level AR, yes it is, you can't really go wrong for the money.

My son recently replaced his stock-stock on his M&P Sport II, with a Magpul Mil-Spec, and it fit perfect.

Of course it did.... the Sport has a mil-spec buffer tube, as I stated above.

I agree... with both points.

Buffer tube dimensions are irrelevant with that stock. Covers are probably made to commercial stock dimensions, since it is larger and would fit both commercial and mil-spec tubes. If the covers rattle from being a little loose, put a little duct tape on the buffer tube to fill the extra space.

Apparently with the Thordsen, part of it includes a buffer tube cover. I was told that I would have to order a "keyed buffer tube" unless the factory buffer tube was 1.16-1.18. I don't make the rules, I only get confused by them

I've shot the Gen-1 15 Sport and it seemed nice from what I can remember! A friend had one and he put a few thousand rounds through it with no issues - various grain weights and types (FMJ, HP, etc.) I remember thinking at the time that I wouldn't even care that it didn't have the dust cover or forward assist - it seemed like a hell of a rifle for the money.

I am trying to decide between the AR556, M&P Sport II and the Black Rain Ordnance new entry level model, the "Spec 15." The Spec15 is about $950 shipped with a Thordsen stock. I couldn't find much on Black Rain though. It seemed like people either loved their guns or said they had problems and nothing was resolved. I saw more of the "best company ever" comments with them, but enough of the negative ones to make me wonder if I shouldn't just go with the Ruger or S&W and save a couple hundred bucks. The purpose is for plinking/target shooting and a defensive option if it ever hits the fan. (During normal rule of law, I would plan to use something like my M&P 40c for home defense during a burglary or home invasion because I am very familiar with it.) I feel like, based on what I've read and heard, the M&P Sport II could cover both of those roles reasonably well.

Strange about that buffer tube. In his u tube videos, he uses, and states, a mil spec tube. And looking at that keyed tube, it's just a modded commercial tube that you can't use a collapsible stock with. Wouldn't a fixed stock with the monsterman grip accomplish the same thing and be cheaper? Another possibility would be the exile machine hammerhead with a fixed stock. And that maybe the way I go, if I have to go featureless.

I was not even aware of those other 2 grip options, so thanks Westie1!

I stopped into my LGS earlier this evening and saw they had just received a Sport II, so the one guy measured the tube on it for me quick and apparently it's 1.17, which would seem to make it not mil-spec. The guy seemed a little rushed though in his measurement (other customers were waiting).

Can anyone who owns an M&P 15 Sport II confirm this measurement of the buffer tube??

Mine measures 1.148, and checked at several points to verify. The hammerhead can be found on amazon for 29.99. And iirc, the exile site has a blurb about it in NY. Another option would be to pin a collapsible stock, and there are you tube vids about how to do it.

Bad measurement on his part (no surprise). The Sport II tube is absolutely mil spec.

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Still carrying my S&W 642

Sorry to resurrect the thread but I just bought a mil-spec Magpul CTR stock for my sport 2 and I cant get it to slide on the buffer tube. I have watched youtube videos of people installing them and they slide right on no problem. I would measure but I don't have measuring calipers, and I don't think a household tape measure will be accurate enough to measure between 1.15 or 1.17 inches. Not sure what to do now, return it and see if a commerial-spec will fit?

Did you undo the friction lock? It's going to be a little tight.

Release the friction lock, pull down on the round metal tabs and slide the stock on the tube. Those tabs can be pulled down with your fingers if you use enough pressure.

It went on, thanks guys. Pulling those 2 tabs on either side just needed a lot more force than i anticipated. I guess I just wasn't compressing the spring enough. All good now.