9mm AR

[ebb]

I have been unable to get a 9mmARto run. I got out another 9mmAR that does run and swapped parts around and I discovered that it is not the upper that is the issue, it's the lower. Then I noticed the charging handle on the PSA lower that is the one that is known to run is way easier to pull than the one that does not run. I am sure that I was sent a rifle length recoil spring and it has a carbine 6 position stock on it and needs a carbine length. Do i just need a standard carbine spring or do the blow back 9s need a special spring?

 

[GNERGY]

Compare the length of the 2 springs next to each other, that will answer that question.
Tarey

 

[457ciSBC]

I have run carbine springs in the ones I have built. Describe “won’t run” in detail.

 

[Cemetery21]

9mms normally ship with a 308 spring (carbine or rifle length). Also, the buffer is much heavier for a 9mm (due to blowback operation). You also need a spacer or a longer buffer. Some 9mm buffers have the spacer built in. If not, you can add about 4 quarters to the back end of the buffer tube. Just enough that the bolt will still lock back and have 1/4" overtravel or less.

 

[garandman]

CMMG Guard has perfected the 9mm AR. Love mine.

Unmodified AR15 lower with MEAN Arms Endo Mag Magpul inserts.

 

[Medic505]

Sell it and buy a Highpoint Carbine, they work.

 

[243winxb]

Do i just need a standard carbine spring or do the blow back 9s need a special spring?

Check with the manufacturer as what is needed. The wrong parts can allow the 9mm to not fully close the action. Gun fires out of battery.

 

[RJTodd]

Advice learned the hard way. It is the ejector. Not the extractor, but the fixed steel ejector. It must be as high and as far centered as possible to the point that a light drag against the bolt is acceptable. I've seen AR 9mm run without an extractor. We found it on the floor after the stage was over. But the ejector must be right against the bolt.

Hope this helps.

Randy

 

[riflewoman]

Standard Carbine spring and 9mm Buffer. The 9mm buffer is heavier.

 

[Rsadams]

I run SPRINCO springs in my AR platforms.... Rifle woman nailed it....If you get board check out SPRINCO web page....

 

[ebb]

The gun tries to chamber a second cartridge before the first is fully ejected. I have removed and replaced the butt stock on an AR 7 or 8 times and never had any problem, but this one was tough to get in and I just decided it was cause the blow back action needed the heavy spring. I am sure now that the parts my daughter gave me included a rifle length spring. "Check with the manufacturer" thats a good one. Ive not been able to get a gun dealer or maker or even a vender to answer the phone in over a year. the buffer is heavier than a normal rifle or carbine buffer so i am going to change the spring. Someone local told me to make this spring work to cut 4 inches off of it, that the rifle spring 4 inches longer than the carbine ????

 

[LuvDog]

I've found that a good HEAVY 9mm buffer is necessary for them to run properly

 

[skeeljc]

Some thoughts:
Make sure there are no "spacers" in the buffer tube that limit the bolt travel.

You should be able to use a rifle length recoil spring. A heavy CARBINE LENGTH buffer is required.

The ejector position is critical in a 9mm AR. You may need to bend the ejector towards or away from the bolt centerline to get reliable functioning. My PSA AR-9 would leave an empty in the action almost 80% of the time. After I bent the extractor in towards the bolt centerline it ejected empties almost 30 feet and was 100% reliable.

Blowback AR's are known trigger killers. Only a few of the available triggers will survive. Hyperfire is one that works well.