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Posted: 8/15/2025 1:53:35 PM EDT
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I’ve put together a 10mm AR, and I’ve finally got enough weight for it to work. Because it’s a blow back, I’ve had to get the BCG and buffer up in weight, and use a stronger spring. I’ve managed to get the BCG(technically the bolt) up to 16.1 oz, and the buffer up to 12 oz, and I’m using an extra power 308 spring. It could be heavier, though I don’t know how. If KAK Industries would redo their extra heavy 9mm weight, and add about 3/8”, that would add about 1oz. Helpful, but I don’t know if it would be enough. I didn’t fire many rounds. This was just to test the build. Using reloads loaded to approx Lyman maximums, the results were interesting. 180gr Win JHP, 10.1gr Blue Dot, new Starline brass. Loads chrono’d at 1550fps. I was rather surprised. Empties looked great, though they were about 16’ away. But, since I was sitting at a bench, that might have affected things a bit. I also tried a maximum load of AA#9. Normally too slow for a handgun, but I thought it might be okay in the longer barrel of the PCC. Velocity was slightly faster, but the bras had visible smiles. One was really bad. So, I think AA#9 is too slow of a powder. I don’t think it can handle any boutique rounds as it’s currently setup. Anyway, I will do some more testing. |
Joined:
Jan 2023
Posts:
194
EE: 100% (18)
PA, USA
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Whats your buffer setup to reach 12 oz? have you read any of blowback9s writing about the 10mm blowback buffer weight recommendations? curious to see how they would play out in the real world as his numbers for .40/10/45 are speculative. This is his article about it. Here |
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I saw a Reddit thread where the poster claimed that a combined BCG/Buffer weight of 26.5-28.5oz was necessary for a 180gr in the 1250fps range. Which is about what my reloads should be. My bolt is about 16.1 oz, and the buffer is 12oz(from Foxtrot Mike), for a total of 28oz. I think that’s not enough, by one to two ounces. That’s why I made the comment about KAK making their weight about 3/8” longer. That would add about 1oz, but I’m not sure that’s enough. There are 2 basic types of AR bolts for the 40/10. One uses a shortened bolt, with an enlarged weight. This one has the most potential for increase, because the weight is larger, it would weigh more in tungsten. So, the bolt alone would weigh about 18oz. So, that would give a combined weight of about 30oz. Close. But, due to the shape of the weight, it would probably be cost prohibitive to make it. https://imgur.com/a/0r6EeIS Edited: It might be just as easy to make a buffer out of solid tungsten. Which would put the weight around 20oz. Which would work just fine. |
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Have you read the GRS thread yet ?? https://www.ar15.com/forums/AR-15/Building-My-First-GRS-Gentle-Recoil-System-by-Blowback9-Lower/15-790568/ Start there, and see what you can gleen from that thread, to improve your buffer function. I would go with an A5 buffer tube, that will allow you to add the 2.5oz Kynshot weight at the front of a buffer. Maybe look into the HD Kynshot buffer while you're at it. https://www.kynshot.com/products/our-products/r15015098-spacer-weight-29/ https://www.kynshot.com/products/our-products/kynshot-rb5015hd-heavy-damped-28/ Ditch the .308 spring, and use the spring chart in the above thread for a flat wire spring that has a higher/heavier spring rate. |
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