S&W M&P15 lower multi caliber concerns...

[zachomega]

Some ar15's have lowers marked multi caliber.

The s&w has no such markings. Not even a 5.56/.223 marking on the lower.

Is there any concern with using other calibers on a s&w lower?

Has anybody done this and had a problem?

I have nothing in mind, but would rather know of any limitations before I buy another caliber upper. Just trying to learn for now.

Thanks,
-Zach

[Sgt.K]

Some ar15's have lowers marked multi caliber.

The s&w has no such markings. Not even a 5.56/.223 marking on the lower.

Is there any concern with using other calibers on a s&w lower?

Has anybody done this and had a problem?

I have nothing in mind, but would rather know of any limitations before I buy another caliber upper. Just trying to learn for now.

Thanks,
-Zach

Personally, I'd be much more concerned if I had a .223/5.56 lower on a .300 build and running into Officer Fudd than having a non-caliber-specific lower with a random upper.

That said, I don't know the *legal* answer to the .300 build scenario.

Experienced folks wanna chime in?

[Emptymag]

I'm almost certain that the only time the marking is of concern is with NFA items which need to be marked.
That's probably the reason "multi-caliber" markings came about in the first place. (for NFA - "multi" covers all bases and allows them to be swapped at will)

[DucatiRon]

Thompson Contender's and Encore receivers have never been marked with caliber.

Traditionally only barrels have been marked with caliber. I think any type of marking on an AR lower designating caliber and building something different is completely unfounded worry.

Save for an NFA build.

[raxar]

There is zero legal requirement for a gun to be the caliber its marked. For NFA stuff it only applies to how you register it, not how the gun is marked.

[Emptymag]

There is zero legal requirement for a gun to be the caliber its marked. For NFA stuff it only applies to how you register it, not how the gun is marked.

For those unfamiliar with NFA... Huh?

[JDA58]

[raxar]

For those unfamiliar with NFA... Huh?

For those who didn't google it like I did. The statement was primarily added to avoid an argument on NFA nuance that I am unaware of.

[Gunsnwater]

Some ar15's have lowers marked multi caliber.

The s&w has no such markings. Not even a 5.56/.223 marking on the lower.

Is there any concern with using other calibers on a s&w lower?

Has anybody done this and had a problem?

I have nothing in mind, but would rather know of any limitations before I buy another caliber upper. Just trying to learn for now.

Thanks,
-Zach

You have this question because gun laws in general don't make any logical sence. Fortunately this time your worries are unfounded.

[zachomega]

So my question was not about legalities and was more safety oriented. No possible damage to myself or others strapping any ar15 upper on an m&p lower?

-Zach