9mm ar-15 conversion

Drummer101 · September 16, 2017, 05:41 PM

I am thinking about getting a 9mm upper for my Colt 6920.

My one concern is about gas in the face. I shoot this rifle left handed with no problems, but I shot the Kel-Tec folding 9mm rifle and that was the first rifle I ever experienced gas in the face where it was a problem.

What I dont know is if it is inherent to the 9mm cartridge being relatively dirty, or design of the 2000 (I am assuming a blow back vs. DI system?).

The other option would be to save for a CZ Scorpion EVO 3 S1 Carbine but that still leaves the same question about gas in the face.

Any one have any experience with doing this?

Thank you

Chainsaw. · September 16, 2017, 10:20 PM

I have an AR in 9mm and Ive shot the scorpion carbine. The AR in 9mm is not at all gassy for me. Straight blow back seems to push it all down the barrel.

The Scorpion is the biggest let down Ive shot in a long time. High points have better triggers.

My advise is go with the 9mm upper. That being said you'll probably want to keep a heavier buffer around to swap out when you put the 9mm upper on. Also of you are gonna be putting a mag block in your AR you can only run straight mags, IE Colt/UZI mags, not that thats a bad thing.

weblance · September 17, 2017, 10:04 AM

Use a gas deflector in the ejection port. The higher cost 9mm uppers all use them. I don't shoot lefty, so I don't know how effective they are...

http://www.jsesurplus.com/rockrivera...ithspring.aspx

bfoosh006 · September 19, 2017, 03:15 PM

"Bark and Blast" from a blowback firearm ( PCC )will always be different compared to a locked breach like a AR15.

You can help minimize the "BnB" by using stiffer springs and heavier buffer weights.

My 9MM Colt pattern PCC is using a .308 Tubbs Flatwire Spring and a 9MM extended 7.5oz buffer.... it runs like a champ.... very smooth.

You can also cut down on the smoky aspect by using clean burning 9MM ammo.

Info on spring weights...

Here are some spring weight measurements from David Tubbs... just food for thought.

A2 (old) - 7.6lb closed, 14.5lb open
A2 (new) - 9.1lb closed, 16.7lb open
Tubb Flatwire - 10.5lb closed, 16.3lb open
Tubb .308 Flatwire - 13lb closed, 16.7lb open
SpringCo White ? (standard) - 8.3lb closed, 16.3lb open
SpringCo Red (extra) - 10.5lb closed, 18.4lb open
SpringCo Orange (increased) - 13.9lb closed, 24.8lb open

IMHO, an extra power spring isn't needed , nor wanted.

I tried both the "Red" and "Orange" ... both caused needless muzzle dip, and were slamming the BCG really hard into the breach face

smee78 · September 19, 2017, 03:51 PM

When I put together a 9mm upper I went with an Oly upper that used Sten mags to feed it. I love it and it works great, haven't had any problems but am not a lefty.

Destructo6 · September 21, 2017, 10:13 AM

Quote:

The other option would be to save for a CZ Scorpion EVO 3 S1 Carbine but that still leaves the same question about gas in the face.

You are not going to get gas in the face with a Scorpion Evo. The ejection port is fairly far forward and that's the only channel for gas to escape.

Quote:

The Scorpion is the biggest let down Ive shot in a long time. High points have better triggers.

The stock 10lbs+ trigger does stink, but can be improved vastly with a $9 HBI spring kit and a few minutes. Mine dropped to just under 5lbs with just the springs.

Thinking about doing a dedicated 9mm AR and there are so many options...so, so many options.

T. O'Heir · September 21, 2017, 11:45 AM

"...this rifle left handed..." More likely because it was a Kel-Tech than anything else. They're not exactly high end kit. A 9mm AR isn't a Kel-Tech. Shot a Colt M-16K years ago with no fuss. Except the Colt rep wouldn't let me keep it.

railroader · September 22, 2017, 09:16 AM

I have an AR9 and I also have the folding Keltec sub 2000. I'm right handed but I can see how the Keltec would put gas to a lefty's face. The sights are short so you really have to get your face down on the stock tube right behind the ejection port. My AR9 isn't like that.

September 16, 2017, 05:41 PM	#1
Drummer101 Senior Member Join Date: October 22, 2009 Location: DFW Posts: 943	9mm ar-15 conversion I am thinking about getting a 9mm upper for my Colt 6920. My one concern is about gas in the face. I shoot this rifle left handed with no problems, but I shot the Kel-Tec folding 9mm rifle and that was the first rifle I ever experienced gas in the face where it was a problem. What I dont know is if it is inherent to the 9mm cartridge being relatively dirty, or design of the 2000 (I am assuming a blow back vs. DI system?). The other option would be to save for a CZ Scorpion EVO 3 S1 Carbine but that still leaves the same question about gas in the face. Any one have any experience with doing this? Thank you __________________ "I would say that we have to make up criteria." OK, which is better for 2 Bantu, 5 Hottentots, and 3 pygmies playing a war march on a calliope at 3 a.m. during a monsoon? Show your work and round to the nearest decimal. -Mike Irwin

September 16, 2017, 10:20 PM	#2
Chainsaw. Senior Member Join Date: September 12, 2015 Location: Issaquah WA. Its a dry rain. Posts: 1,774	I have an AR in 9mm and Ive shot the scorpion carbine. The AR in 9mm is not at all gassy for me. Straight blow back seems to push it all down the barrel. The Scorpion is the biggest let down Ive shot in a long time. High points have better triggers. My advise is go with the 9mm upper. That being said you'll probably want to keep a heavier buffer around to swap out when you put the 9mm upper on. Also of you are gonna be putting a mag block in your AR you can only run straight mags, IE Colt/UZI mags, not that thats a bad thing. __________________ Just shoot the damn thing.

September 19, 2017, 03:51 PM	#5
smee78 Senior Member Join Date: July 14, 2008 Location: South Carolina Posts: 2,918	When I put together a 9mm upper I went with an Oly upper that used Sten mags to feed it. I love it and it works great, haven't had any problems but am not a lefty. __________________ We know exactly where one cow with Mad-cow-disease is located, among the millions and millions of cows in America, but we haven't got a clue where thousands of illegal immigrants and terrorists are

September 21, 2017, 11:45 AM	#7
T. O'Heir Senior Member Join Date: February 13, 2002 Location: Canada Posts: 12,453	"...this rifle left handed..." More likely because it was a Kel-Tech than anything else. They're not exactly high end kit. A 9mm AR isn't a Kel-Tech. Shot a Colt M-16K years ago with no fuss. Except the Colt rep wouldn't let me keep it. __________________ Spelling and grammar count!

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September 17, 2017, 10:04 AM	#3
weblance Senior Member Join Date: October 3, 2012 Posts: 1,229	Use a gas deflector in the ejection port. The higher cost 9mm uppers all use them. I don't shoot lefty, so I don't know how effective they are... http://www.jsesurplus.com/rockrivera...ithspring.aspx

September 19, 2017, 03:15 PM	#4
bfoosh006 Senior Member Join Date: February 17, 2009 Posts: 1,089	"Bark and Blast" from a blowback firearm ( PCC )will always be different compared to a locked breach like a AR15. You can help minimize the "BnB" by using stiffer springs and heavier buffer weights. My 9MM Colt pattern PCC is using a .308 Tubbs Flatwire Spring and a 9MM extended 7.5oz buffer.... it runs like a champ.... very smooth. You can also cut down on the smoky aspect by using clean burning 9MM ammo. Info on spring weights... Here are some spring weight measurements from David Tubbs... just food for thought. A2 (old) - 7.6lb closed, 14.5lb open A2 (new) - 9.1lb closed, 16.7lb open Tubb Flatwire - 10.5lb closed, 16.3lb open Tubb .308 Flatwire - 13lb closed, 16.7lb open SpringCo White ? (standard) - 8.3lb closed, 16.3lb open SpringCo Red (extra) - 10.5lb closed, 18.4lb open SpringCo Orange (increased) - 13.9lb closed, 24.8lb open IMHO, an extra power spring isn't needed , nor wanted. I tried both the "Red" and "Orange" ... both caused needless muzzle dip, and were slamming the BCG really hard into the breach face

September 22, 2017, 09:16 AM	#8
railroader Senior Member Join Date: February 8, 2000 Location: Tucson Arizona Posts: 1,756	I have an AR9 and I also have the folding Keltec sub 2000. I'm right handed but I can see how the Keltec would put gas to a lefty's face. The sights are short so you really have to get your face down on the stock tube right behind the ejection port. My AR9 isn't like that.