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Posted: 7/6/2007 6:58:19 AM EDT
| Does anyone have any experience with a CMMG 9mm upper? I plan to buy one for my soon to be SBR, but I want to know what kind of bolt CMMG uses in their 9mm uppers. I've read all the info about ramped and unramped bolts, and all the hammer info as well. I'd like to be able to keep a hammer in my lower that would also work with a 5.56 upper. |
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CMMG is a good company and IMHO has the best barrels. Ramping is a gunsmithing feature that isn't necessary, but neither is that stupid 'notch' that can lock your bolt halfway back. Ramping is probably a good idea as long as it's done right. I just use a standard rounded hammer and a extra heavy buffer in all my setups. |
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CMMG 9mms are the colt pattern, and probably get their bolts from the same company RRA does, which is basicly a FA 9mm bolt. I think ramping the bolt allows the use of a standard 5.56 hammer (with the notch), if I'm wrong someone will correct me. The DPMS and CMMG hammers work in both 5.56 and 9mm without ramping the bolt. |
DPMS hammer in unramped 9mm if your lucky and a few have been here . Mike ETA: I ramp bolts so you can use any ar15 hammer you would like |
Ramping generally requires the standard UN-notched hammer, or M16 hammer (without the autosear tab) Another question, why does CMMG not offer a 10.5" barrel? what's with the 11.5"? I know that COULD add some reliability in a 5.56 gas system, but it won't affect a 9mm sys. |
I just talked to them last Monday about that. I have a CMMG 10.3" 5.56 barrel and wanted a 9mm to match it. They said maybe in the future but no plans anytime soon for the shorter setup. I really wanted the chrome lined CMMG barrel for my build but unfortunately they use a 5/8-24 thread instead of the 1/2-36(or 28) that everyone else uses. If you plan on using a suppressor on them this could be a problem. I talked to SWR and the Trident9 cannot accept an endcap to fit the 5/8-24 threading and it looks like the Gemtech Trinity won't either. Back to the original topic, ramping is a good idea for use with any 5.56 hammer, notched or not. This has to do with the speed at which the hammer is reset as the bolt goes across it. I wanted to share my same receiver as I use for my 5.56 SBR but decided to go ahead and go with the dedicated 9mm setup. I think in the long run it will be a better option. |
Crap! to the part highlighted in red. Adding a suppressor was going to be my next step after getting my SBR stamp. After reading about the Trident 9 I had decided that's what I was going to get. |
Any reason you don't just 3-lug it? I know SWR offers a 3-lug for the Trident. Not sure about the Gemtech, but the Trident is supposed to be the quietest anyway. In fact, that's going to be my next purchase. |
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When I had my 16" RRA 9mm upper, I had all kinds of FTF and FTE. After getting my Form 1 back, I went with a TROS 3 lug barrel and a CMMG 9mm bolt. They told me that they make the bolts themselves in-house. Not sure if I buy that but regardless the bolt works 100%. I also wanted to use the same trigger/hammer setup, a RRA NM 2 stage trigger, with multiple uppers. Me being a graduate of WECSOG, I took a dremel and a hand file to the bolt and ramped it myself. It was easy, took about 15 minutes and runs perfectly with the RRA 2 stage trigger. After getting rid of a couple "less than cooperative" Colt mags, I have about 2500 rounds thru it now with no problems. |
From CMMG's website: 11.5 9mm Stripped Barrel New production stripped 11.5" 9mm barrels. Features include chrome lined chamber and bore, MP testing, 9mm chambering, 1/10" twist, mil-spec parkerizing, and 1/2x36 threads. Barrels have not been drilled for taper pins. Barrels are engraved "CMMG MPC 9mm NATO 1/10". |
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