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Posted: 9/26/2025 1:38:27 PM EDT
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I tested my 10mm PCC today. This is a build that I’ve been working on for some time. I finally got the bolt and buffer combination up high enough. Empties were hurled 6-10 feet away, depending on the powder. None of them have bulged, so brass appears to be reusable. Velocity is about 1600fps with a 180gr bullet. So, I now have a carbine that can use the same ammo as my handgun. I actually found an article about making an additional buffer weight for a 9mm. The idea appeared sound. So, I made one for my 10mm. It got my moving weight up to 32.5oz(16.1+10.8+5.6). That, plus a Griffin Armament Extra Powerful 308 Spring(+15%) seems to have done the trick. Now, more testing and sighting it in. |
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Originally Posted By EDL: That would be sweet. Wonder what the angle of the cut on the bolt lugs will be on that, 65 degrees? If you look at old posts when the Dissent came out for 45. Some asked if it could handle 45 super and CMMG posted that NO, the Dissent couldn't handle it since it was NOT tuneable and that the old Banshee could since it used the buffer tube and you could also use the tuning weight kit. I suspected they would have a hard time to ever come out with a 10mm Dissent being bufferless and I'm skeptical that will ever come out which doesn't bother me at all since I personally don't like bufferless setups as they are less tuneable and if you get them to run full auto, they shoot way too fast. I'm waiting for the 10mm Retrofit to come out and if it does, I will use it for 40SW suppressed. Like I did in the past. It worked but still ate ejector springs every 800 rounds or so. I don't really have an interest in 10mm. I do have bunch of .40SW brass that I would load up and leave at the range.  |
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Originally Posted By EDL: You mention liking the 40/10mm bolt Originally Posted By EDL: You mention liking the 40/10mm bolt I also noticed below a few days ago..... This is new to me that CMMG has two different bolts for 40SW. I wonder if the 40SW bolt for a 16" barrel is really just a 67 degree 10mm bolt.  what did you have to do to the bolt to get it to fit to the smaller 9mm case head? |
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OP here. I did a minor test this morning. It was only to test functionality. There was no accuracy testing, or chronographing done. The one with the rifle length buffer tube(“receiver extension”), 10” in length, had ejection about 2-3 feet away. About perfect. Its set up is 11oz buffer, 2.5oz KynShot buffer spacer, and 5.6oz homemade tungsten weight. The bolt weighs 16.1oz. Total moving weight is 35oz. Length of the moving buffer weights is 4”+1”+.81”, for a total of not quite 6”. Since I’m using a rifle length tube, and to prevent the bolt from getting caught by the buffer retainer pin(yes, I’ve had that happen), I put a short(2.5”) buffer reversed as a spacer. I can probably get away with using a 9mm buffer spacer. But that’s a test for next time. The second gun has a Carbine A5 buffer tube(7.75”). I used the same weights for this gun that had been in the rifle tube. But, because of the shorter tube, no buffer spacer was used. Empties stll went 6-10 feet. So, I either need to increase the buffer weight a bit, or use a stronger spring(Red). The spring is a bit easier, but the weight is probably better. I have no idea why the difference. Ammo was my reloads, using AA#9, which is slower than my preferred powder(Blue Dot). But, I’m running out of BD, so I thought I would try AA#9. It seems to work fine, but more testing will tell. |
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Originally Posted By amphibian: BarrelXchange made full auto UZI bolt that work with both .40SW and 9mm. When opened up for 40SW still works fine for 9mm. I figured since it works great in my UZI's, it would be fine for the CMMG RDB and it is. The diameter under the rim is nearly identical for 9mm and .40S&W, which is why you can often use the same shell plate when reloading. It's also why Glock .40S&W guns can easily run 9mm with just a conversion barrel and magazine. |
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Originally Posted By Sailormilan2: I tested my 10mm PCC today. This is a build that I’ve been working on for some time. I finally got the bolt and buffer combination up high enough. Empties were hurled 6-10 feet away, depending on the powder. None of them have bulged, so brass appears to be reusable. Velocity is about 1600fps with a 180gr bullet. So, I now have a carbine that can use the same ammo as my handgun. I actually found an article about making an additional buffer weight for a 9mm. The idea appeared sound. So, I made one for my 10mm. It got my moving weight up to 32.5oz(16.1+10.8+5.6). That, plus a Griffin Armament Extra Powerful 308 Spring(+15%) seems to have done the trick. Now, more testing and sighting it in. Curious what lower receiver and barrel you're using and how reliably they feed rounds? |
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