I want a 9mm AR, use a dedicated lower or just an upper

I used a standard AR lower with a kit, AR slick side upper 9mm bolt and a Faxon barrel. I'm well over 1000 rounds and not a single problem. It shoots 1" groups at 50 yards with a 4x scope.

The only advantage I've found in the magwell adapters is that you can (sorta) swap around to find the best magazine for your economy. But, the mag adapters are a compromise, and compromises can be wobbly.
Which is where a dedicated lower, commited to a single magazine design can really shine (if the magazine also shines).

Upper only is less expensive to start. But, only if you are using the upper on a limited basis. But, a dedicated lower means being able to grab-n-go for a range trip.

That's just my 2¢

https://www.meanarms.com/products/detail/endomag-9mm

Another option.

You could go with a standard lower and use the Endomags mentioned above. Still going to have to have a buffer set up for 9mm.

IMHO, the easiest, most efficient and enjoyable way is to just bite the bullet and get a dedicated lower. My range is out back and I do quite a bit of shooting just cause I get the itch. Grab'n' Go works for me.

I have gone through magwell block in AR lower to dedicated 9mm Glock lowers to Just Right Carbine to Endomag kit using PMags.

• Magwell block - I do not recommend this option as you have to disassemble the lower/mag release button/bolt release to install/remove the block. And even with different magazines, I did not experience reliable feeding as bullet nose must bump/contact the feed ramp of the block to enter the chamber/barrel. With metal PSA block, my feed rate was 98% reliable. I do not recommend polymer ProMag block as thin polymer warped and block was essentially useless.
• Dedicated 9mm lowers - I used dedicated lowers using Glock mags and while experienced reliable feeding as bullet nose is pointed towards chamber/barrel but they did not support Last Round Bolt Hold Open (LRBHO). There are dedicated lowers now that offer LRBHO but slightly different "manual of arms" than AR15.
• Just Right Carbine has modular magwell design so you can change calibers to 9mm/40S&W/10mm/45ACP using Glock/M&P/1911 magazines. Reliable feeding but no LRBHO and different "manual of arms" than AR15.
• Endomag kit inside PMags - This is the option I now recommend to others as you can use any standard lower and have reliable feeding along with LRBHO and "manual of arms" is exactly same as regular AR15.

As to buffer weight, Pistol Caliber Carbines using blow back action must use heavier buffer to hold case in the chamber long enough to not bulge the case base.

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

I have a 5.56 lower with a magwell because it's an SBR. Didn't want the paperwork for yet another gun for the relatively more rare use of a 9mm.

Your situation may be different of course. Think of why you want an AR 9mm specifically. If a new gun, why not a CZ, MPX, or so on? Dedicated platforms that take advantage of it.

Mine runs 100%, but I know others have had issues with magwell blocks.

Also, I have not had to change my buffer, much less spring. Know others who had to, and who did not. Not all guns work badly/oddly. Some do. No obvious way to tell before you try it

PSA is a great way to go. You can get a dedicated lower using Glock mags or the Colt stick mag version.

If you don’t mind finishing an 80% lower these folks have dedicated lowers. What’s cool is the also have them for M&P and Sig.

I found them as I’d like one that takes M&P mags.

https://aaomfg.com/ar-lowers-parts/

Will you be happier with 1 1/2 or 2 guns?

11/2 gun being two uppers and only one lower vs. a dedicated .223 and 9mm rifles.

George Dickel said:

Nothing frustrates me more than unreliability. The ability to quickly and easily swap an upper makes having only one lower no problem. Being cheap, the reduced cost of the single lower appeals to me. The main thing I'm concerned with is reliability. If I can get good reliability from a single lower I will go that route.

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Funny I sort of agree but hold the opposite view.
I’m all for being frugal, but prefer to have backups when possible. So since lowers are cheap, I’d rather have a few.
Plus the fact that ARs are adult Legos means you can mix and match and buy parts and swap.

Personally if I have a extra upper I’m going to buy a extra lower and vice versa right now prices are pretty cheap might as well buy a second gun