9mm AR question

[kb4ns]

Are different brands of 9mm AR's pretty much interchangeable like their 5.56 cousins? For example, will a RRA 9mm upper function with a Spike's 9mm lower or do different manufacturers do things totally different?

[Guest kickstand]

Olympic uppers are different, other than that I think everything is Colt style, so they mesh up. You can run a 9mm upper on a standard AR lower with a mag block, 9mm (or heavy) buffer, and a 9mm hammer. 9mm hammer works fine with the .223 bolt. I have a RRA upper/bolt that I run on a Spike's SL15 lower. Upper is for sale in sig....

[kb4ns]

Upper is for sale in sig....

If only it was 16"... :-\

[jeffmem]

Usually you have to change out the hammer and buffer on the lower for them to run right.

[kb4ns]

Usually you have to change out the hammer and buffer on the lower for them to run right.

You mean if you were using a 223 lower, right? You wouldn't need to do that if both upper and lower were made for 9mm, just different brands?

[Guest kickstand]

You mean if you were using a 223 lower, right? You wouldn't need to do that if both upper and lower were made for 9mm, just different brands?

If you buy a factory complete 9mm lower it will come with a 9mm hammer installed. If you're throwing one together yourself either try to find a 9mm LPK (I dunno if they sell these) or buy a hammer in addition to the other parts/LPK. .223 hammer works only with .223 bolt, 9mm works with both. Unless of course you modify the hammer/bolt.

[kb4ns]

Ok, that's what I was thinking. Thanks.

[flyanything]

What's the difference in the hammer and buffer compared to .223? Lighter? Stronger?

[kb4ns]

I dunno. I got my first ever 9mm AR today. I was told it has a .223 hammer in it because that's how Spikes Tactical rolls. I'm confused.

[Dolomite_supafly]

I dunno. I got my first ever 9mm AR today. I was told it has a .223 hammer in it because that's how Spikes Tactical rolls. I'm confused.

It could have a ramped bolt. If the 9mm bolt has been ramped it will work with a 223 hammer otherwise you do need a 9mm specific hammer. Another reason to have a ramped bolt is it is less stress on the hammer and trigger pins. The pins can snap if using an unramped bolt with a blowback gun, which the 9mm is. I do believe Spikes Tactical do indeed ramp their bolts.

Dolomite

[Dolomite_supafly]

What's the difference in the hammer and buffer compared to .223? Lighter? Stronger?

I have found that a 9mm will work with a standard AR buffer and spring. And to add to this some guns function better with the heavy buffer. It is all a matter of finding the right ballance. My personal 9mm uses a standard AR buffer and spring and runs great.

As far as the hammers go here are the differences if you do not have a ramped bolt. If your bolt is ramped you can use the 223 hammer. Otherwise you will need to swap hammers along with your upper.

Dolomite

[50 cal]

I run an Olympic 9mm upper. I had to use the 9mm hammer and a 9mm specific buffer for it to run right.

I have a mag well block that let's me use unmodified Sten mags. It has been flawless. It never fails to get attention at the range.

Edited November 8, 2010 by 50 cal

[Dolomite_supafly]

It never fails to get attention at the range.

Mine always gets taken to any shoots I go to. It is fun and cheap to shoot. And anybody can shoot it without much fuss. My wife liked it better than the 223 because of the muzzle blast. I always use it or my 22 lr AR to introduce new shooters to the AR because for some the 223 is too much noise and concussion.

Dolomite