9mm AR build.

[mcmurry]

So I finally got an AR last year and now I doing some long range planning on an AR build. I would like a 9 mm AR pistol. If you were going to build one, where would you start?

 

[Ed4032]

When I built mine the first decision is Glock mags or Colt style mags. If Glock then get a dedicated lower for the glock. I went Colt style. Regular lower with an insert for the mags. I wanted to be able to convert it to any caliber. Runs like a sewing machine and is lots of fun.

 

[wally]

Regular lower with an insert for the mags. I wanted to be able to convert it to any caliber.

Be aware that there are two styles of inserts (aka mag blocks) top loading and bottom loading. If you plan to switch between 9mm and calibers using the full mag well very often make sure you get a bottom loading mag block as removing and re-installing the BHO gets old fast!

The IMHO highly inflated price of the mag blocks usually makes the dedicated Glock mag lowers a less expensive build overall, but the versatility could be worth the extra cost. Good Glock mags and Colt style (modified Uzi) mags cost about the same so this is a wash. Usually the dedicated Glock lowers don't activate the BHO unless you buy a more expensive dedicated lower (like the Quarter Circle 10) whereas the Colt style do activate it unless you are actually using Uzi mags that have been modified.

You may also need a heavier "9mm buffer" which is another impediment to easily swapping calibers.

 

[Wisco]

I built an SBR from a CMMG lower that takes Colt-style mags. It’s fun, but it’s not 100% reliable even after working on the ejector.

I didn’t see any options at the time to buy a quality lower that takes Glock mags, but if I was building now I would buy a Glock compatible lower instead.
View attachment 775090

 

[wally]

I don't think the Glock mag model will really buy you any more reliability (I have both styles), the real issue is that the blowback 9mm AR has too high bolt/carrier velocity so it takes very little fouling or FOD in the magazine to cause a feed failure, using the heaviest buffer you can find helps, but I start getting feed failures after things get dirty, I doubt the fact I mostly shoot them suppressed doesn't help.

 

[Hokie_PhD]

So I finally got an AR last year and now I doing some long range planning on an AR build. I would like a 9 mm AR pistol. If you were going to build one, where would you start?

I’ve been researching them, but I’ve only found one that uses M&P mags. I’m hoping that more will become available and prices come down.

 

[bbqreloader]

mcmurray, check out thread for more info...https://www.thehighroad.org/index.p...d-you-use-and-why.825314/page-3#post-10734382

 

[saiga308]

So I finally got an AR last year and now I doing some long range planning on an AR build. I would like a 9 mm AR pistol. If you were going to build one, where would you start?

start with building a 40 cal s&w round much better hitting power down range

 

[bbqreloader]

easier to go with 9mm if your wanting to do a budget build, piece by piece. Going 40 starts upping the price and wait till you want to trip to 45

 

[saiga308]

easier to go with 9mm if your wanting to do a budget build, piece by piece. Going 40 starts upping the price and wait till you want to trip to 45

yeah but its worth every penny

 

[LiveLife]

I would like a 9 mm AR pistol. If you were going to build one, where would you start?

Having done both the mag blocks and dedicated Glock lowers, I would suggest the dedicated lower build for more reliable feeding. Most bolts these days are cut to be compatible with Glock magazines.

I use standard AR lower parts kit with standard AR hammer and haven't had any issues as illustrated in the PCC build thread - https://www.thehighroad.org/index.p...d-you-use-and-why.825314/page-3#post-10702392

FYI, with carbine recoil spring, I found 19-22 oz combined weight of buffer and bolt produces more comfortable felt recoil. 16-18 oz combined weight produces harsher felt recoil - https://www.thehighroad.org/index.p...es-and-what-parts-did-you-use-and-why.825314/

PSA bolt 14.7 oz + PSA buffer 5.3 oz = 20 oz combined weight and produces comfortable felt recoil with various 9mm loads. For longest "in battery" time for more consistent chamber pressures, use heaviest buffer that will reliably cycle the bolt. With 20 oz combined weight, my PCCs will cycle even lighter target loads (115 gr RMR FMJ with 4.6 gr W231/HP-38 or 4.1-4.2 gr Red Dot/Promo) - https://www.thehighroad.org/index.p...-what-am-i-in-for.824002/page-3#post-10606695

For reference:

- H1 buffer weighs 3.8 oz
- H2 buffer weighs 4.6 oz
- H3 buffer weighs 5.4 oz