AR-57 Buffer weight for 16" Barrel?

Discuss rifles chambered for the 5.7x28mm; P90, PS90, and AR57.
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spicoli
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AR-57 Buffer weight for 16" Barrel?

Post by spicoli » 04 Mar 2022, 08:02

Hello All,

New AR-57 SLC (gen 3) owner here with the 16" barrel. Problem is the upper I received did not include the factory buffer so I need to purchase one. What was the factory buffer weight for this model? Do other weights work better? Any insight would be appreciated.

Thank you in advance!

Toprudder
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Re: AR-57 Buffer weight for 16" Barrel?

Post by Toprudder » 25 Nov 2022, 20:15

The buffer is also a different length (3.025”) from a standard buffer (3.25”) so I am not sure a standard buffer will work.

My buffer is 4.8oz.

Armed Eye Doc
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Re: AR-57 Buffer weight for 16" Barrel?

Post by Armed Eye Doc » 29 Nov 2022, 20:05

I checked the buffer on my AR57 (gen2 iirc). It is 3.075 inches. My scale died and I haven't replaced it, but I believe it is in the 4.8 oz range as well. I have used my upper on a lower with a binary trigger without changing the buffer from a standard length H2. I had no function issues with it at all.

Toprudder
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Re: AR-57 Buffer weight for 16" Barrel?

Post by Toprudder » 05 Dec 2022, 14:45

After running a test this past weekend, I now fully believe a standard carbine length buffer will work. I also believe a heavier buffer will be better than the 4.8oz buffer.

The first rounds from my Panzer AR57 had shoulders that were pushed out, making me think the cases were extracting too quickly, allowing the high pressure to push the shoulders out. So, I decided to try the heaviest buffer I had, a 7.5oz buffer from a 9mm carbine. Although that buffer is much longer than a standard carbine buffer, It would pull back just far enough to manually lock the bolt open. There were no problems manually chambering rounds. I had no problems with cases ejecting, but I had a few failures to feed/chamber. I attribute that to the length of the buffer causing it too shorten the stroke and cycle too quickly. I’m going to order a standard length heavy buffer to try.

On the plus side, the cases fired with the heavier buffer all looked really good.

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panzermk2
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Re: AR-57 Buffer weight for 16" Barrel?

Post by panzermk2 » 05 Dec 2022, 18:12

FYI Shoulder movement while under full pressure is normal for the 5.7 and part of it's operation.
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Toprudder
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Re: AR-57 Buffer weight for 16" Barrel?

Post by Toprudder » 06 Dec 2022, 15:37

panzermk2 wrote:
05 Dec 2022, 18:12
FYI Shoulder movement while under full pressure is normal for the 5.7 and part of it's operation.
Yeah, that is true, but I’ve gotten a lot of 5.7 brass shot from other guns that don’t have the shoulders pushed out nearly as much as those from my AR57. I do understand the shoulder will move, that is a problem with any bottleneck cartridges shot from blowback actions, 357sig PCCs are known for it.

I like to tinker, and I am curious if I can get a heavier buffer working. They work really well in 9mm carbines.

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Re: AR-57 Buffer weight for 16" Barrel?

Post by panzermk2 » 07 Dec 2022, 09:43

Pics of the brass?
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panzermk2
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Re: AR-57 Buffer weight for 16" Barrel?

Post by panzermk2 » 08 Dec 2022, 14:46

This is normal movement of the shoulder.

EA S4
MKII Gen2 pistol.

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Jay Wolf
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"Engineers, the oompa-loompas of science!"

Be'ein Tachbulot Yipol Am Veteshua Berov Yoetz
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