9mm Ar build ? and Suggestions ?

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bushwacker's

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Hi friends my first question is about the buffer tube and Spring I was reading that I should be using a heavy buffer and Spring because a heavy buffer and spring are needed as the 9mm is a blowback system...not a gas one , I'm not entirely sure that makes sense to me but I don't have the upper in hand as of yet .

I learned from a friends down south today that there is a lot going on in that Mag block that comes with the kit I bought , he was telling me that there are several parts that are changed in a dedicated 9mm lower bolt catch extension , feed ramp and ejector .
He did say I should buy a 9mm Buffer Assembly and Spring CMMG who he said stocks all the parts I should need in the USA only lists the Buffer Assembly no Spring .

Any help would be great trying to get everything together so this goes smoothly ,anyone has the Buffer Assembly/Spring let me know .
Bushy
 
bushwacker's said:
Hi friends my first question is about the buffer tube and Spring I was reading that I should be using a heavy buffer and Spring because a heavy buffer and spring are needed as the 9mm is a blowback system...not a gas one , I'm not entirely sure that makes sense to me but I don't have the upper in hand as of yet .

I learned from a friends down south today that there is a lot going on in that Mag block that comes with the kit I bought , he was telling me that there are several parts that are changed in a dedicated 9mm lower bolt catch extension , feed ramp and ejector .
He did say I should buy a 9mm Buffer Assembly and Spring CMMG who he said stocks all the parts I should need in the USA only lists the Buffer Assembly no Spring .

Any help would be great trying to get everything together so this goes smoothly ,anyone has the Buffer Assembly/Spring let me know .
Bushy
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I am in the process of building a quarter circle 10 9mm AR. I am using a phase 5 pistol buffet tube and a blitzkrieg 9mm hydraulic buffer. I went with the hydraulic buffer because they are longer so you don't need spacers, and the hydraulic function is supposed to help with not breaking bolt catches on 9mm AR's. I've done some research and the shorter buffers can cause the bolt to go too far back and slam the bolt catch eventually breaking them. Some people use or add a 9mm buffer spacer, other 9mm specific buffers are already longer. The hydraulic buffer is longer and has the hydraulic cushion action at the end to softer it even further. Yes you want heavy for the buffer, 9mm specific ones are 5.5+ ounces. Also I was suggested to use a .308 buffer spring, I got s JP polished one

I should be getting my bolt and barrel tomorrow so I will know how it all works very soon
Here's my setup you can see the hydraulic buffer in the 2nd pic
IMG_3017_zpsjuh5jnxm.jpg

IMG_3012_zpsx191whvc.jpg
 
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Beautiful build thus far ! this project is getting morse costly at every turn , thanks so much for answering my question so well , very excited to see and hear from you as you get that beast to the range !
Please keep me informed very sweet unit.
Bushy
 
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bushwacker's said:
Beautiful build thus far ! this project is getting morse costly at every turn , thanks so much for answering my question so well , very excited to see and hear from you as you get that beast to the range !
Please keep me informed very sweet unit would .
Bushy
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It doesnt have to be too expensive, but dont use me as an example I have problems with online ordering. So my builds usually cost 3X more then what they have to

For the buffer I went with the spend once cry once, as I hear you can have major issues with bolt catch breakage. However a normal 9mm buffer does not have the same $150 price tag of the hydraulic. You can get a dedicated 9mm buffer for around $40-40 CAD

Out of stock at the moment but you can grab a 9mm buffer for $25-30 US
http://www.brownells.com/search/index.htm?k=9mm+buffer&ksubmit=y
https://www.rainierarms.com/catalogsearch/result/?cat=0&q=9mm+buffer
 
JohnnyP636 said:
It doesnt have to be too expensive, but dont use me as an example I have problems with online ordering. So my builds usually cost 3X more then what they have to

For the buffer I went with the spend once cry once, as I hear you can have major issues with bolt catch breakage. However a normal 9mm buffer does not have the same $150 price tag of the hydraulic. You can get a dedicated 9mm buffer for around $40-40 CAD

Out of stock at the moment but you can grab a 9mm buffer for $25-30 US
http://www.brownells.com/search/index.htm?k=9mm+buffer&ksubmit=y
https://www.rainierarms.com/catalogsearch/result/?cat=0&q=9mm+buffer
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Where did you get the upper and lower? That's the lower that takes Glock mags, correct?
 
WRH said:
Where did you get the upper and lower? That's the lower that takes Glock mags, correct?
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Yes that is a small frame glock mag lower, it will take 9mm or .40 cal Glock mags. I plan to buy their .40 cal bolt and barrel soon so I can shoot both 9mm and .40 with a barrel/bolt swap

###### armory is the Canadian dealer for QC10, they also became a dealer for Gibbz arms and SLR rifleworks for me so they could supply the side charging upper and rail.

Great company

LOOKS LIKE CGN DO NOT LIKE THE COMPANY AS THE NAME IS BLOCKED FROM THIS SITE! I will PM you the company

I will try to get out to the range tomorrow or the next day, I just received my barrel and bolt
IMG_3026_zpsoqtle3m2.jpg

I just have to assemble the upper, and pop out to my friends machine shop to bore out my 5.56 muzzle brake to accept 9mm
 
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bushwacker's said:
Hi friends my first question is about the buffer tube and Spring I was reading that I should be using a heavy buffer and Spring because a heavy buffer and spring are needed as the 9mm is a blowback system...not a gas one , I'm not entirely sure that makes sense to me but I don't have the upper in hand as of yet .

He did say I should buy a 9mm Buffer Assembly and Spring CMMG who he said stocks all the parts I should need in the USA only lists the Buffer Assembly no Spring .
Click to expand...

9mm AR's are pure blowback operated. The weight of the BCG and buffer plus the recoil spring are designed to balance out the recoil forces generated by the 9mm bullet. You will need a 9mm buffer, which is heavier than a heavy 556 buffer. There is no such thing as a 9mm spring.
 
JohnnyP636 said:
Yes that is a small frame glock mag lower, it will take 9mm or .40 cal Glock mags. I plan to buy their .40 cal bolt and barrel soon so I can shoot both 9mm and .40 with a barrel/bolt swap

###### armory is the Canadian dealer for QC10, they also became a dealer for Gibbz arms and SLR rifleworks for me so they could supply the side charging upper and rail.

Great company

LOOKS LIKE CGN DO NOT LIKE THE COMPANY AS THE NAME IS BLOCKED FROM THIS SITE! I will PM you the company

I will try to get out to the range tomorrow or the next day, I just received my barrel and bolt
IMG_3026_zpsoqtle3m2.jpg

I just have to assemble the upper, and pop out to my friends machine shop to bore out my 5.56 muzzle brake to accept 9mm
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Where did you source the barrel? I'm looking for one like that.

Pm will edit out the name as well. You have to space it or add punctuation where it isn't needed mid name or something to break it up.

Edit: nevermind. AZ tec with no space.
 
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Due to a related question asked of me a few days ago, I had cause to weigh a 9mm AR bolt and buffer and compare that to the weight of a Sten bolt. Turns out they are nearly identical. Sten bolt 600g. 9mm AR bolt + buffer 590g.

In my personal 9mm AR I use an extra heavy custom made steel-carbide buffer. This gun functions flawlessly with the extra BCG weight. When it comes to pure blowback guns, reciprocating bolt weight is your friend.
 
Suputin said:
Due to a related question asked of me a few days ago, I had cause to weigh a 9mm AR bolt and buffer and compare that to the weight of a Sten bolt. Turns out they are nearly identical. Sten bolt 600g. 9mm AR bolt + buffer 590g.

In my personal 9mm AR I use an extra heavy custom made steel-carbide buffer. This gun functions flawlessly with the extra BCG weight. When it comes to pure blowback guns, reciprocating bolt weight is your friend.
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I dont have the greatest scale but I popped my bolt onto the scale we have at work to weigh packages. The bolt alone came out to 0.9 Lbs, add 6oz for my buffer and Im roughly 567 grams bolt and buffer
 
JohnnyP636 said:
I dont have the greatest scale but I popped my bolt onto the scale we have at work to weigh packages. The bolt alone came out to 0.9 Lbs, add 6oz for my buffer and Im roughly 567 grams bolt and buffer
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My bolt is an older design and has a bigger internal weight than the Colt pattern bolt. Still, your 567g is pretty close to the 600g I got.
 
Suputin said:
My bolt is an older design and has a bigger internal weight than the Colt pattern bolt. Still, your 567g is pretty close to the 600g I got.
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Mine is cut for Glock mags but it also has internal weight added to the bolt. The whole back area that is hollow on a regular BCG has been filling in with a weight that is pinned in place. Also there is som much material added to the bold, it has a groove cut into it just enough for the trigger hammer to clear it.

If I had a more accurate scale I would assume its actually heavier then the 567g I got on my crappy scale

I have also read that depending on your barrel length, you can use more or less weight in bolt. I will have to see how my work out as is and go from there, hopefully it gets me close enough to run decent. Ive just started to mess around with different weight buffers in my other AR's and it can make a huge difference in how the rifle functions.

I got out to a buddies shop yesterday to bore out my muzzle brake, I was going to find the center on the mill, but I figured Id be better off asking my buddy to bore it out on his lathe. Woke up late today and traffic was stupid, so Im going to try and make it to the range tomorrow to test it out. Ive got some AE 124g and 147g to run through it
IMG_3037_zpskejnybwf.jpg
 
JohnnyP636 said:
I have also read that depending on your barrel length, you can use more or less weight in bolt. I will have to see how my work out as is and go from there, hopefully it gets me close enough to run decent.
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The only way barrel length would affect a blowback gun is if it either shortens or lengthens the bore pressure dwell time. A short bbl would result in a shorter dwell on the bore pressure and a longer would have the opposite effect. However this would require either a very short bbl or a fairly long one. An inch or two either way isn't going to make much difference at all.

The ammo itself would have a much greater effect. Light loads may cause short stroking and very heavy loads would result in overly high bolt velocities.

What you are going to find is that a blowback SMG is pretty tolerant of ammo and bbl length.
 
Suputin said:
The only way barrel length would affect a blowback gun is if it either shortens or lengthens the bore pressure dwell time. A short bbl would result in a shorter dwell on the bore pressure and a longer would have the opposite effect. However this would require either a very short bbl or a fairly long one. An inch or two either way isn't going to make much difference at all.

The ammo itself would have a much greater effect. Light loads may cause short stroking and very heavy loads would result in overly high bolt velocities.

What you are going to find is that a blowback SMG is pretty tolerant of ammo and bbl length.
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Sounds good the only experience I have with SMG so far is my KRISS Vector in .45 acp. Love that gun but .45 gets expensive in these little guns that are a blast to rapid fire. So rather then buy another KRISS in 9mm I decided to build this to fill that 9mm SMG gap. 10 rd mags are awesome too! Many other options were only 5rd capacity
 
Davie Sprocket said:
So wish I had picked up one of the sten mag 9mm kits, I think olympia made them, remember that name for some reason. Nice build, very jealous.
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Mine is an old Oly Arms model. They are a bit different as the ejector is a spring that is held into the upper via a cross pin which requires two small holes to be drilled in the upper. It originally came on a carry handle type upper but I retrofitted the ejector and its pin to a more modern flat top upper. The whole thing works really well. Has been very reliable with 147r subsonics.
 
When i built my spikes 9mm. It was wolff XP buffer spring and H3 buffer. Even then, the recoil impulse was stronger than my 16" 223.

I believe slash buffer uses a 7oz buffer for the 9mm apllication.

Ps: i did run the spikes buffer spacer to limit the travel of the bolt
 
I don't want to de rail this post but we should have a dedicated thread to this subject as I have been thinking of building a 9mm AR but no almost nothing about it. I think it would be great fun! The building and the shooting. I can see the exchange being an issue but that is for another thread.
 
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