School me on AR lowers M&P 15...

[flyfishinjunkee]

I have a S&W M&P 15 and Anderson AM-15 rifles. Both are standard 16" barrel rifles with no frills. I have been looking at pistol uppers (10" side charge AR-Stoner 223 REM from Midway specifically, and others from Palmetto)and wondering if a pistol upper will work on either of the aforementioned lowers. I heard that the S&W lower is not "milspec" and thus may not work, but trying to get a solid answer on this. If there are differences between the lowers, please help me undersatnd what they are as well as interchange-ability.... Thanks!

 

[ColbyBruce]

If you purchased both your rifles as rifles, not as a pistol or “other” firearms, they must remain rifles unless you SBR it.

Parts should swap out, I have swapped uppers and lowers on several brands and only had issues with polymer lowers.

 

[RCL-09]

Basically placing a shorter than 16" barrel on a rifle lower is a felony as it would be classified as an unregistered short barrel rifle (SBR).

Any AR purchased as a rifle must remain a rifle unless you register it.

If you purchase a receiver alone you can make one or the other (rifle or SBR) But once you do so it must essentially remain what you originally made it.

If you want an AR piston buy a new receiver and build it into a pistol and leave it in that configuration.

 

[Muss Muggins]

It will work, but unless done properly, as others have mentioned, it may land you in prison. If your state has a law like Missouri’s new one prohibiting local law enforcement from enforcing federal gun laws, you might be okay for a while. Good luck . . .

I have a S&W M&P 15 and Anderson AM-15 rifles. Both are standard 16" barrel rifles with no frills. I have been looking at pistol uppers (10" side charge AR-Stoner 223 REM from Midway specifically, and others from Palmetto)and wondering if a pistol upper will work on either of the aforementioned lowers. I heard that the S&W lower is not "milspec" and thus may not work, but trying to get a solid answer on this. If there are differences between the lowers, please help me undersatnd what they are as well as interchange-ability.... Thanks!

 

[flyfishinjunkee]

Basically placing a shorter than 16" barrel on a rifle lower is a felony as it would be classified as an unregistered short barrel rifle (SBR).

Any AR purchased as a rifle must remain a rifle unless you register it.

If you purchase a receiver alone you can make one or the other (rifle or SBR) But once you do so it must essentially remain what you originally made it.

If you want an AR piston buy a new receiver and build it into a pistol and leave it in that configuration.

So, if I purchase a bare receiver, I can put the upper on it, but i cannot put the upper on a receiver that came as part of a whole rifle (such as the ones I have?)? Such as... Order all parts from Palmetto and assemble myself? Thanks this was just the info I was looking for

Also, assuming this was legal......... What is the interchangeability? Are there any differences functionally between the M&P and a "milspec" lower?

 

[ColbyBruce]

As stated above, use a stripped receiver or a receiver built as a “pistol” with a brace or bare tube.

[Also, assuming this was legal......... What is the interchangeability? Are there any differences functionally between the M&P and a "milspec" lower?]

S&W M&P have never given me a problem. I have swapped parts between Bushmaster (original and recent), Olympic Arms,S&W, Windham Weaponry, RRA, Skyjacker Defense, PSA, Anderson, DPMS, and a few others.

 

[flyfishinjunkee]

Thanks... Lgs has one complete so I'll probably go that route.

Sent from my SM-G981V using Tapatalk

 

[67tempest]

I have assembled literally dozens of AR's using just about every lower and upper combination imaginable and only had an issue with one. The rear takedown pin lug on the upper was nicking the rear of the lower when you closed it. I dressed down the high spot with a file and touched it up with a sharpie, problem solved.

 

[double-dipper]

OP, The short answer; Yes you could buy a completed upper and put it on your lower, but not league! The AR must start life as a "pistol" as others have stated you're converting your rifle to a SBR not a pistol.

Your other question; I have a S&W M&P and it is "mill spec" I don't like that term as it gets tossed around for just about everything AR, it should be "Industry Standard"

As an example I just completed a PCC Pistol Caliber Carbine for Steel Challenge. The manufacture of the upper stated it was "mil spec" I asked them how many 9mm uppers have they sold to the military.

 

[RCL-09]

So, if I purchase a bare receiver, I can put the upper on it, but i cannot put the upper on a receiver that came as part of a whole rifle (such as the ones I have?)? Such as... Order all parts from Palmetto and assemble myself? Thanks this was just the info I was looking for

Also, assuming this was legal......... What is the interchangeability? Are there any differences functionally between the M&P and a "milspec" lower?

So, swapping uppers and lowers, as far as fit and reliability is not an issue. I regularly swap rifle uppers on my rifle lowers and have no issue with reliability or accuracy. My hunting rig consists of a Rock River lower, with their match trigger, and a 6.8SPC and .223 uppers. Interchangeability is not an issue.

As others have stated "milspec" is mainly a marketing term.

The legal technicalities come in when you have an AR rifle and pistol and begin swapping uppers and lowers between the two.

Specifically to your question, "if I purchase a bare receiver, I can put the upper on it, but i cannot put the upper on a receiver that came as part of a whole rifle (such as the ones I have?)? "

If the bare receiver is built as a rifle (i.e. you put a stock on it) then you cannot legally put an upper on it that has a barrel shorter then 16".

If the bare receiver is built as a pistol (i.e. you put a brace and less than 16" barrel on it) then you cannot legally put an stock on as that would be a short barrel rifle.

As to this "I have a S&W M&P 15 and Anderson AM-15 rifles. Both are standard 16" barrel rifles with no frills. I have been looking at pistol uppers (10" side charge AR-Stoner 223 REM from Midway specifically, and others from Palmetto)and wondering if a pistol upper will work on either of the aforementioned lowers." if you put that upper on those lowers,while it would work, it is a violation of the law.

 

[bamashooter]

Let's clear this all up. You will have no problem with fitment and compatibility. Like anything in life, there exists a one in a gazillion chance of a problem. Enjoy.