Will a 15T Upper go on any mil-spec lower?

grb · Feb 12, 2014

Hello Gentlemen,
I've migrated over from the 15-22 forum because I recently built my first AR15 Lower (alum Anderson) and want to purchase a complete S&W 15T Upper (#812010) to finish the build. I've found the complete 15T Upper for around $680 in 2 places.

Since I'll be buying online I can't check the fit prior to purchase.

So, as the topic asks, do you guys see any reason the 15T Upper Assembly wouldn't fit or function properly on my Anderson Lower?

I used the Search function but most of what I found was related to putting the 22 Upper on the M&P15 Lower or adding a new Upper to a S&W Lower.

Thanks for your input. I'll take suggestions, as well, but don't want to spend more than $700 on a complete Upper since I've already got $300 (incl mags) in the Lower. I know, a $50 stripped Lower turned into a $300 bottom half.

#overbudget lol

cyphertext · Feb 12, 2014

As long as the lower and upper are in spec, it will fit.

JaPes · Feb 12, 2014

The AR-15 platform is built upon standardized specs. As long as your lower is true to spec, any true to spec upper will fit.

grb · Feb 12, 2014

Thanks Fellas, that's what I was hoping to hear.
I was led to believe S&W stuff was a little different. So I was a little worried.

With 3000+ posts between the two of you, I'm sure ya'll either talk a lot or know what your talking about. I'm going with the latter :-0

cyphertext · Feb 12, 2014

grb said:
I was led to believe S&W stuff was a little different.

As long as we are talking the true AR-15 from S&W, the dimensions of their uppers and lowers are spec. Where S&W differs from other brands like Colt, is in barrel materials, twist rates, semi auto bolt carrier vs. full auto bolt carrier, etc... But even these parts can be swapped in and out of other AR-15s.

The story changes when dealing with the 15-22. You can't fit a 15-22 upper on an AR-15 lower, or vice versa. Those are made with different measurements to insure that someone does not try to use an AR upper on the 15-22 lower.

JaPes · Feb 12, 2014

grb said:
With 3000+ posts between the two of you, I'm sure ya'll either talk a lot or know what your talking about. I'm going with the latter :-0

For me, it's a little of both.

sithlord · Feb 12, 2014

grb said:
Thanks Fellas, that's what I was hoping to hear.
I was led to believe S&W stuff was a little different. So I was a little worried.

With 3000+ posts between the two of you, I'm sure ya'll either talk a lot or know what your talking about. I'm going with the latter :-0

It's possible that you are thinking that the S&W M&P 15-22 is a little different (since you stated you came from the 15-22 forum), and you would be CORRECT. Neither the 15-22 lower or upper are AR-15 MIL-SPEC.

That is, you cannot put a AR-15 MIL SPEC upper onto an M&P 15-22 lower. And you cannot put the M&P 15-22 upper onto an AR-15 MIL SPEC lower.

The M&P 15 line (Sport, T, X, etc) are MIL-SPEC upper and lower, and, as others have said, are interchangeable with other mil-spec AR parts.

Will a 15T Upper go on any mil-spec lower?

grb

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cyphertext

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JaPes

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grb

Member

cyphertext

US Veteran

JaPes

Member

sithlord

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