AR 15 mechanic?

[looseprojectile]

It has came to pass that I bought a new lower to dedicate to my 9mm upper.

Now when i bought the butt stock I got a rifle stock as I can't abide the adjustable stocks. Now I am told I have to use a heavy carbine buffer and spring with the 9mm cartridge. The carbine stock tube is shorter than the rifle tube. Therefore the carbine buffer and spring is too short to fit the rifle tube.
I will need to fabricate some kind of additional buffer and/or spring so that my rifle and buffer can work with the heavier thrust of the 9mm cartridge. Maybe a silicone rubber plug inside the spring for the buffer to strike?
When I first got the 9mm upper I shot it by just putting it on my .223 lower and it seemed to work great. What am I missing? Help!!!

Life is good

[StarMetal]

It has came to pass that I bought a new lower to dedicate to my 9mm upper.

Now when i bought the butt stock I got a rifle stock as I can't abide the adjustable stocks. Now I am told I have to use a heavy carbine buffer and spring with the 9mm cartridge. The carbine stock tube is shorter than the rifle tube. Therefore the carbine buffer and spring is too short to fit the rifle tube.
I will need to fabricate some kind of additional buffer and/or spring so that my rifle and buffer can work with the heavier thrust of the 9mm cartridge. Maybe a silicone rubber plug inside the spring for the buffer to strike?
When I first got the 9mm upper I shot it by just putting it on my .223 lower and it seemed to work great. What am I missing? Help!!!

Life is good

Because the 9mm in the AR15 is a blowback it requires a heavier buffer, which the carbine buffer is. I believe you could use the carbine buffer with the rifle length spring. The carbine buffer is still too light I believe. If that won't work you can buy heavier rifle buffers. Eventually shooting with the wrong buffer will wreck something in the system. Probably would take awhile though.

Go to this page and see all the buffers and note the weight differences between them:

http://www.biggerhammer.net/ar15/buffers/

http://ee.ar15.com/ItemView.aspx?iid=45514

Joe

[CWME]

Can't you cut a piece of round plastic to use as a stop? I am thinking of the plugs used in shotgun magazines to limit the number of rounds... Why wouldn't that let you use the carbine parts?

[looseprojectile]

After looking at the differences in buffers that Joe provided I believe I can turn a longer buffer out of nylon. I looked all over the internet for that site. I have a piece of nylon a foot long and an inch and a half in diameter. I am trying to do this at little cost so that I can do other things with the savings. I also might look into an AR 10 spring.
I will do what it takes to make it right. Thanks gents.

Life is good

[StarMetal]

Let me explain again. They aren't so much a buffer in the sense that they absorb the recoil of the bolt/carrier group, they play a big part in delaying the bolt from opening so the pressure in the barrel can drop. You noticed they all have weights in grams or ounces.

Not the plastic spacers is not a good idea.

It would be wise here to buy the 9mm buffer or one equally as heavy.

Joe

[bohica2xo]

Don't make a replacement buffer out of nylon - the bolt will beat the **** out of things.

The 9mm buffer is basically solid steel. It adds mass to the bolt assembly. Do not replace it with lighter parts.

If you want to run the 9mm upper on a rifle stock, make a nylon slug for the rear of the buffer tube to make up the length difference. Drop the slug in, then load the buffer & spring assembly on top of it.

9's are known for high bolt speeds, and things like broken hammers & hammer pins. This gets worse with the wrong buffer.

B.

[GabbyM]

You need the 9mm buffer as it's heavier than the 5.56mm buffers. They sell an extension for using the carbine buffer in the rifle stock.

With a blow back operated 9mm rifle the mass of the bolt and buffer is what determined delay in opening after firing. The buffer moves with the bolt so is part of this mass.

Here are links to the space and a 9mm carbine buffer.

http://www.brownells.com/.aspx/sid=51603/pid=23212/sku/9mm_Fixed_Stock_Buffer_Tube_Spacer

http://www.brownells.com/.aspx/sid=49277/pid=23212/sku/9mm_Carbine_Buffer

Same stuff at Rock River Arms.
http://www.rockriverarms.com/index.cfm?fuseaction=category.display&category_id=244

[looseprojectile]

I'm catching on now thanks all. I do believe I have a handle on the subject .

Life is good

[looseprojectile]

You guys are wonderfully tolerant and patient. I am catching on now.

Here is what I propose.
I will dissasemble the rifle buffer and add lead to 8 - 10 ounces. The bolt carrier in my .223 AR has a loose piece sliding back and forth inside it. Does that work like a recoil reducer? Then add a spacer inside the stock tube to limit the movement of the bolt . Doesn't need to travel 4 inches.
The spacer will tend to compress the spring adding more push with the heavier buffer. At least I think I am going in the right direction with this, no?
Also I will look into the profile of the hammer and the radius on the bottom of the 9mm carrier. I believe I can make it work.
This 9mm rifle will probably be used for trading stock when completed though I would like for it to be as good as possible. I have recently acquired an urgent need for a DPMS .308 rifle:lol:.
Thanks again for your enlightenment.

Life is good

[rickt]

Why don't you use the carbine buffer and glue the collapsible stock fast to the buffer? That is what the manufactures did to make NY compliant M4's besides grind the lug off and change the name of the thing on the end of the barrel to muzzle break.

[bohica2xo]

If you want to use a rifle length buffer in the rifle stock, no length adjustment is necessary. The spring preload is right with the proper tube & buffer assembly.

A mass adjustment is necessary on the rifle buffer. If you drive the pin out, and remove the rubber bumper you will find a set of steel slugs & rubber discs.

The slugs & discs fit loosly in the assembly, and serve to dampen out the rebound of the bolt carrier slamming into the barrel extension. The 9mm buffer has a floating head & one rubber disc to do this job.

You can increase the mass by adding some lead to the rifle buffer. It is close to right as-is, so by removing a steel slug or two & replacing it with lead you can adjust the weight. Keep the slugs & rubber disc arrangement, it is necessary for reliable operation. A cut down 50 cal linotype bullet works great for this.

As for the "loose piece" in your 223 carrier - that ain't right. There should be no loose parts inside the carrier behind the firing pin. This can lead to either jamming or uncontrolled full auto operation.

If you meant "loose parts" in the recoil buffer, then yes the slugs & discs should rattle when you shake the buffer.

B.

[StarMetal]

It sounds like the loose piece in your 223 carrier is a David Tubbs type carrier weight. You should set the 9mm up correctly, but you're not seeming to want to follow the good advice here to do so. You will end up paying consequences if you don't follow that advice.

In my opinion the carrier weights are the wrong way to go on the 223/5.56 AR15's. AR15's are over gassed to insure their operation under all conditions and climates. What extra weights do is beat the carrier against the barrel extension which is not a good thing to do. I find the best method to tune the AR15 is with an adjustable gas valve.

This has nothing in relation to your 9mm as it's blowback operated and has no gas system like the rifle caliber AR15's.

Follow the advice here and enjoy your 9mm rifle.

Joe

[looseprojectile]

I don't know how that word "carrier" got where buffer should go.
I shot the rifle a few minutes ago and it functions really good. Used some 147 grain subsonic and some reloads with 115 grain cast, no difference in POI.
I have taken apart the buffer and added a steel piece in the place of an aluminum weight inside the buffer which is the standard rifle unit. I might have gained an ounce. I radiused the bottom of the carrier so it doesn't hang up on the hammer. The hammer in the lower parts kit is the wide hammer from DPMS, works fine. I may radius the top corner just to make it run smoother. I can feel about three or four impulses during recoil.
The beauty of it is at thirty yards I shot a ragged hole a little to the right of the bull that measures one inch wide by two inches high. About thirty rounds. Was resting/leaning on a tree.
This putting together of parts to make an AR must not be rocket science as I can do it![smilie=l: With help from some of my friends.

Life is good

[Just Duke]

I had one and had to many issues. It was a Olypic Arms ***.

[82nd airborne]

i might be too late to help, but rock river makes a tactical entry stock that is an A2 stock but shorter. it works with carbine buffer springs. also affordable. if you cant find what im talking about i have one not in use, maybe we can work somethin out. aaron