building custom buffer for suppressed 9mm AR?

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mr fixit
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building custom buffer for suppressed 9mm AR?

Post by mr fixit »

Wondering if anyone here has any experience with 9mm AR carbines, Specifically, making a longer than normal custom buffer to increase weight in the blow-back action as well as limit travel of the carrier/bolt.
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John A.
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Re: building custom buffer for suppressed 9mm AR?

Post by John A. »

There are a few ways you can make heavier than normal buffers. For that matter, I have seen a lot of 5oz, 8oz, and up to 10oz buffers made for 45/10 that you can buy already.

I have also seen tungsten buffer weights that you can swap out with existing buffer weights.

As for limiting overtravel of the bolt, https://9mmar.com/ sells a short plastic buffer that takes up the extra space unnecessary for the 9mm. And some guys have used nothing more than a stack of quarters in the back of the buffer spring.

For my Colt style build, I also found it necessary to modify my mag catch to make it a little longer than a standard catch by putting some stick/spot weld onto the contact face of the catch and then filing it down smooth. I think Rock River makes those now without the need for all of that. And probably wouldn't be necessary on one of the newer style glock style builds.

But I preferred to go my own way with my mods.

I warn you now though, it took some time to do and is truly custom to my gun. And it was also an odd buffer tube to begin with (meaning it was longer than normal collapsible looking style).

Back in the ban days, Bushmaster used a pinned stock that looked like a collapsible, but was in fact a fixed stock.

The tube was A1/A2 length. But it had the thing on the bottom that looked like a collapsible stock. But was not milled out or drilled to accept a collapsible stock. That's how bushmaster got the approval to use it. The stock also didn't move. It was pinned in place rearward/open.

After that stock had been collecting dust since the fall of the AWB, I finally drug it out of the box and wiped the dust off of it.

Since it is incapable of accepting a rifle stock (in this case either a collapsible or fixed stock), I shortened it down enough to not fall into atf's arbitrary "grey area" in regards to length of pull and also machined a groove in the rear of it to install a tailhook pistol brace.

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Since the tube is longer than a collapsible buffer tube, this would allow you to make up to a rifle length buffer. Or, you can make a spacer like I did and essentially make the buffer any length you wanted in between carbine and rifle length. The trick would be to find one of those old ban stock tubes. I already had mine from when the ban died.

Here is a picture of the spacer that I made from a piece of wood dowel just until I got the length right. Later, I machined a piece of aluminum rod instead of the wooden one. But the pics below all show the wooden dowel.

My setup uses standard collapsible buffer springs and buffers. But doesn't allow overtravel because of the buffer.

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garredondojr
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Re: building custom buffer for suppressed 9mm AR?

Post by garredondojr »

There are a couple of companies who make extended heavyweight buffers that address this issue. in addition to spacers. many have used quarters in the buffer tube as a limiter.
cutterspc
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Re: building custom buffer for suppressed 9mm AR?

Post by cutterspc »

https://photos.app.goo.gl/xFqm5MJAYBKMFxYo9

They do sell them and rather cheaply. I made mine cause I always have to do stuff the hard way, I'm stupid like that, lol.

I have a lathe and mill, and I enjoy making chips. Fun easy project if you have the tools.
blade1668
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Re: building custom buffer for suppressed 9mm AR?

Post by blade1668 »

Late to the party, I didn't make my own, I used A5 buffer for one of mine. I have changed the tungsten weighs around in a few buffers. The good thing about using A5 buffer or building your own is it will keep 9mm brass out of hammer pocket and shorten bolt stroke, less slamming into bolt catch and breaking it.
I have used the quarters trick a few times on it and a 308 rifle after suppressing it. On 308 I went with a SpringCo spring(s)
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mr fixit
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Re: building custom buffer for suppressed 9mm AR?

Post by mr fixit »

Just to give an update, I turned a buffer from CRS. Ended up about 5" long, weighs 9.2oz. Installed and tested with WWB 147gr. Build is a NFA Glock mag lower, 5.5" 9mm barrel, using a standard mil-spec buffer tube and standard carbine spring. Total weight of bolt/carrier and buffer is right at 23oz.
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John A.
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Re: building custom buffer for suppressed 9mm AR?

Post by John A. »

1-1/2 lb of weight forcing the bolt closed battering it and the barrel extension seem a little overkill?
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fishman
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Re: building custom buffer for suppressed 9mm AR?

Post by fishman »

John A. wrote: Sat Dec 14, 2019 12:09 pm 1-1/2 lb of weight forcing the bolt closed battering it and the barrel extension seem a little overkill?
That's why the CMMG radial delayed blowback system exists
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mr fixit
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Re: building custom buffer for suppressed 9mm AR?

Post by mr fixit »

It doesn't get full travel since it is longer than standard. Im pretty sure it doesnt make up a lot of momentum with the short travel
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Re: building custom buffer for suppressed 9mm AR?

Post by a_canadian »

While something like radial delayed blowback would be nifty in a 9mm PCC (something ECCO suggested in another thread where I'd mentioned something about this subject), unfortunately retrofitting such a system to an existing carbine might prove... challenging. So with mine I'll be working along similar lines, substituting tungsten for some of the steel buffer weight, moderating spring tension and travel, maybe changing the urethane buffer stop for something of different dimensions if necessary, all in aid of delaying blowback a bit more to reduce the uncorking noise at the ejection port while preserving feed and ejection with my favourite cartridges - 147gr stuff seems happy for mine.
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