I would like to learn how to build a 9mm AR with a AR-15 stripped lower.
You build it the same way as an ar15 but you need a mag block. Here is a glock based one but you can also get them for colt style mags.
https://palmettostatearmory.com/psa-custom-9mm-glock-compatible-mag-well-conversion-block.html
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I just did mine. There’s really only one or two minor differences. You’ll want a longer and heavier buffer. I went with an 8oz extended buffer.
You’ll also need some way to feed 9mm ammo, whether it’s a magblock that will allow you to use pistol magazines, or the Mean Endomag inserts, which converts a Gen2 or Gen3 5.56 Pmag into a 30 rnd 9mm mag. I went with the Endomag. Everything else is the same.
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Did you use a PA9 Build Kit (https://palmettostatearmory.com/psa-gen4-4-9mm-1-10-nitride-5-lightweight-m-lok-railed-moe-ept-sba3-pistol-kit.html)?
Are these the same build kits/parts or would I need a standard AR-15 lower build kit?
No, I didn’t use a PA9 kit. I used a mil-spec standard lower…well, actually it was my Let’s Go Brandon lower. So, a mil-spec lower, some sights/optic, some ammo, and either a magblock or Endomag inserts, and you should be golden. The only other thing is the buffer. The kit that you listed had PSAs 9mm buffer, which is probably about 5.5oz. I don’t know how long it is. If you’re using a standard buffer tube, it needs to be right at 4.0 inches long. If it’s shorter, then you’ll need to use something as a spacer at the back of the tube; either a proper spacer, quarters, a piece of PVC, something.
Edit: I believe that in the PA9 kit that you listed,
everything but the buffer and the brace are the same as a standard lower build kit. I ended up getting a Brownells Lower Parts Kit, just because that’s what my LGS had in stock.
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Can anyone tell me what the correct buffer weight would be needed for
a 9mm to feed correctly and not jam ?
Well, there’s a number of things that affect feeding. What bullets are you using?
I’m using the 8oz extended buffer from MidwayUSA, and it’s doing great in my 16" carbine.
Too many things are in play…ammo, buffer, spring, even feed ramp/cone. Give us some specifics about your gun.
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Hi, sorry about the delay been really busy with doctors. The upper is a bear creek arsenal 9mm 16" barrel and full auto bolt. The lower is a sharps brothers 9mm “jack” stripped lower stripped receiver. it has a rare breed trigger and the rest of the parts are PSA with a 9oz.buffer. the ammo used is Remington arms 9mm 115 gr FMJ. any help in this will be appreciated.
Hi, have been busy going to doctors. The ammo is Remington arms 9mm 115 GR FMJ. The upper is a bear creek arsenal 16" with full auto bolt. The stripped lower was sharps brothers the “Jack” 9mm the trigger is a rare breed, and remaining parts are PSA with a 9 oz. buffer. any / all help appreciated.
You need to talk to Rudy at Macon Armory. With that mismash of parts he may be the only one that can help you. My money is on the feedramp being wrong.
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Thank you. I will try to get un contact with him when I can.
I’m interested in building a 9mm AR, from looking at complete 9mm AR pistols around the webs, many are bufferless. I was under the impression that because it is blowback not DI, no buffer was needed.
If it is roller delayed or if it functions like an AK you don’t need a buffer tube. Otherwise you do.
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when i built mine i talked to the guys at american resistance that are about the best in the industry at setting one up. They said to use at least a 5 oz buffer and a 308 carbine buffer spring.
buffer in a blow back 9 is probably more important then a 556. It not only controls your feeding but also serves to keep the case in the chamber until the powder is burned and its why you use a heavier buffer in a 9mm. Use to light of a buffer and the case will come out of the chamber to fast and you will have cases spliting and even exploding.
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