9mm AR15

NateTheShake · Jun 4, 2011

So what is EVERYTHING needed to build a 9mm AR15. I haven't gone down this road yet, but I'm thinking it'd be a fun project. It's going to be an SBR, but I didn't see a point in posting this just in the NFA section. So what do I need?

Nate

K-Romulus · Jun 4, 2011

1) Upper receiver group: either a Colt style (RRA, Spikes, etc.) or Olympic.
2) Magazine well adapter for the 9mm magazines (unless you use a purpose built 9mm lower that it already engineered to only take 9mm magazines)
3) 9mm buffer (yes, you should get one, I learned the broken bolt catch lesson when I forgot to switch buffers)
4) 9mm magazines

If it is a dedicated 9mm Colt-style rifle, then you will just need to get a 9mm hammer along with the standard AR15 parts kit (and maybe a 9mm bolt catch?). If you just plan on swapping Colt-style uppers as needed, the only permanent part required is a rounded BCM or DPMS style hammer, and I think you can get away with using that hammer on a dedicated build.

I am not up to speed on the Olympic-type rifles, so I won't say anything about those.
That's about it . ..

JeepDriver · Jun 4, 2011

Mag block, hammer and buffer. Hammer can be skipped with a raped bolt. RRA has a lower that eliminates the need for the mag block.

Look for TROS barrels, they have the 3 lug, then get a 3 lug adaptor forth Trinity and your set.

NateTheShake · Jun 4, 2011

JeepDriver said:
Mag block, hammer and buffer. Hammer can be skipped with a raped bolt. RRA has a lower that eliminates the need for the mag block.

Look for TROS barrels, they have the 3 lug, then get a 3 lug adaptor forth Trinity and your set.

Looking at RRA's site... I could just buy the complete lower from them, have it stamped etc, and then get the pistol upper.

Any info on the Oly Arms Glock version? Is it pretty much the same as the others minus the mag well or does it have a totally different upper as well? I'd really like to follow that option if it's possible to use any other upper as I have a huge stockpile of Glock mags already. Seems like it would be the best compliment to what I've already got on hand.

canuck · Jun 4, 2011

NateTheShake said:
Looking at RRA's site... I could just buy the complete lower from them, have it stamped etc, and then get the pistol upper.

Any info on the Oly Arms Glock version? Is it pretty much the same as the others minus the mag well or does it have a totally different upper as well? I'd really like to follow that option if it's possible to use any other upper as I have a huge stockpile of Glock mags already. Seems like it would be the best compliment to what I've already got on hand.

Info on Oly? Yeah, don't buy it.

I have built 3 9mm guns. As jeep said buy the TROS barrel. Mark is good people.

BTW - this topic has been discussed in detail previously

montoya32 · Jun 4, 2011

I just built a 9mm upper and I live the CMMG upper. I did go to a 9mm buffer that is stiffer and got a Rock River Arms magwell adapter. I would suggest using the bushmaster plastic mags. The CProducts mags I have stick a little, but the plastic msg I have works flawlessly.

StantonCree · May 21, 2016

Can I get a regular lower parts kit? There was some question as to the hammer.

sailskidrive · May 21, 2016

Check out the CMMG dedicated lowers; IMO they seem to work better than stacking the tolerances of a random lower with a mag block.

The next step will be acquiring some quality Metalform mags. Visit Precision Firearms over the line in WV for the mags.

Boss94 · May 21, 2016

mpdc4511 said:
Can I get a regular lower parts kit? There was some question as to the hammer.

Yes if you have a ramped bolt you can use a standard hammer.

Alphabrew · May 21, 2016

I've built two of them, it's fun. The upper is really easy since there's no gas system to deal with.

Alphabrew · May 21, 2016

mpdc4511 said:
Can I get a regular lower parts kit? There was some question as to the hammer.

Yeah, not all hammers work. A lot of guys modify full auto AR-15 hammers for their 9mm builds. I used a POF drop in trigger, works great. The Colt rifles use full auto hammers:

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rouchna · May 21, 2016

Alphabrew said:
Yeah, not all hammers work. A lot of guys modify full auto AR-15 hammers for their 9mm builds. I used a POF drop in trigger, works great. The Colt rifles use full auto hammers:

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+1 on the POF Trigger. :thumbsup:

dontpanic · May 21, 2016

rouchna said:
+1 on the POF Trigger.

I have a POF trigger in my 9mm as well. It was recomm to me by the good folks at Gun Connection.

Absolutely no problems with it.

Mdeng · May 21, 2016

mpdc4511 said:
Can I get a regular lower parts kit? There was some question as to the hammer.

Holy zombie tread :sad20:

Yes a standard lower parts kit can be used for a 9mm build. If you are using a 9mm dedicated lower it may already have a few parts installed. My YHM lower came with the bolt stop, feed ramps and ejector already installed.

What upper to you plan to use. A1 still has a few of the vintage Colt A1 uppers in stock. :party29:

I did find a problem with my notched hammer. The bolt will hang up on a notched trigger. I switched it out with an ALG ACT trigger that works very well and won't break the bank.

StantonCree · May 21, 2016

Mdeng said:
Holy zombie tread

Yes a standard lower parts kit can be used for a 9mm build. If you are using a 9mm dedicated lower it may already have a few parts installed. My YHM lower came with the bolt stop, feed ramps and ejector already installed.

What upper to you plan to use. A1 still has a few of the vintage Colt A1 uppers in stock.

I did find a problem with my notched hammer. The bolt will hang up on a notched trigger. I switched it out with an ALG ACT trigger that works very well and won't break the bank.

Yeah but this project is gonna take a second otherwise I would have snagged it when I got the lower from Greg.

With just buying the MR73 and the lower I need a wallet break.

I also don't know what "look" I'm going for. It seems 99% of these things are SBRed when I google images 9mm AR. I know I want one but now I don't know what feel I want for it.

outrider58 · May 21, 2016

For those looking to fill all the gaps, this is very useful. Start at #28

http://www.mdshooters.com/showthread.php?t=191060

slowpoke · May 21, 2016

outrider58 said:
For those looking to fill all the gaps, this is very useful. Start at #28

http://www.mdshooters.com/showthread.php?t=191060

Truth!

StantonCree · May 21, 2016

outrider58 said:
For those looking to fill all the gaps, this is very useful. Start at #28

http://www.mdshooters.com/showthread.php?t=191060

Awesome thank you

Mdeng · May 21, 2016

I picked up my lower and the upper in a partial trade with Greg. It's currently built as a pistol waiting on a tax stamp then it will get a new buffer tube and aN original Colt SMG stock.

photoracer · May 22, 2016

I suggest you get one of the shallower angled pistol grips. If you shoot it like that you will get some serious wrist pain from the short stock setup. Go to PSA and look up B5 grips.
I used a ramped bolt with one of my Timney drop in triggers on my build.

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