9mm upper change

[smith m4]

I am considering buying a 9mm upper for my S&W M&P15 in 5.56.

Whose upper should I buy? I am currently looking @ Rock River.

Can I just pop the 5.56 upper off and pop the 9mm upper on or do I have to change a bunch of other things?

I do know I will have to get 9mm mags can someone tell me what kind to get and where to find them.

Any other advice on this subject please feel free to add.

[Don D]

I was going to make a post just like yours, but thought since you already asked the question I'd just piggy-back on yours. Hope you don't mind.

My only variation to the question is that the 5.56 M4 that I'd like to convert to 9mm is a full-auto (post-sample) Rock River Arms gun.

[vinesr6]

You need the whole 9mm upper of course, bolt/carrier is different.
You need a new hammer unless you have the DPMS or similar styled hammer.
You need a mag block, Hahn is considered a very good choice, I have a dedicated SBR lower w/a pinned Colt 2 piece blocks.
Lots of ammo, a 9mm buffer and mags. CProducts just introduced their new 9mm mags check them out. I have some on order, but currently using converted mags by M60Joe (no problems at all.)

Hope that helps....

[smith m4]

Does anyone know if the hammer on the Smith is the right style?

[C4IGrant]

Does anyone know if the hammer on the Smith is the right style?

Most likely not unless it looks like the pic below.

The RRA 9mm uppers are about the best IMHO. CProducts will be releasing 9mm mags VERY soon. This will be the best option for mags.

I have the RRA 9mm uppers in stock and will have the CProducts mags available as well.



C4

[smith m4]

Once I change the hammer will the new hammer for 9mm work for the 5.56 or will I have to change the hammer everytime I change the upper?

[Robb Jensen]

A non notched AR15 hammer will work (looks a lot like a M16 hammer but w/o the tail for the automatic sear).

[davemcdonald]

Grant
Do you have a ball park for the CP 9mm mags?

Dave

[John Hearne]

Once I change the hammer will the new hammer for 9mm work for the 5.56 or will I have to change the hammer everytime I change the upper?

What he said. Will a 9mm hammer work with a 5.56 upper? Need to know about M-16 carriers and AR-15 carriers.

Thanks in advance.

[Robb Jensen]

What he said. Will a 9mm hammer work with a 5.56 upper? Need to know about M-16 carriers and AR-15 carriers.

Thanks in advance.

As I said before a non-notched hammer won't know the difference in carriers. In a 9mm AR the bolt and carrier are the exact same part.