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View Full Version : 9mm AR builds, mixing CMMG w/ RRA


///D
05-27-2009, 10:24 AM
I am in the process of a 9mm AR build and am using CMMG as the main components (Upper & Lower) but am using the RRA conversion kit (mag-block, hammer, buffer). The RRA kit advertises it to be used w/ RRA uppers etc. Although it "shouldn't" be a problem...has anyone had any compatibility/fitment issues mixing and matching these 2?

foxtrotuniformlima
05-27-2009, 10:37 AM
You are alright. A non-9mm upper will not have the funky deflector and since the 9mm BCG has no FA on it, there is no need for the FA assembly on the upper.

NSR500
05-27-2009, 10:38 AM
No problems on mixing and matching with one condition, the hammer & bolt combo.
If you are using an RRA bolt, you should use their hammer. If you are using the CMMG, or any other ramped bolt, you can use your standard hammer.

///D
05-27-2009, 10:44 AM
No problems on mixing and matching with one condition, the hammer & bolt combo.
If you are using an RRA bolt, you should use their hammer. If you are using the CMMG, or any other ramped bolt, you can use your standard hammer.

The 9mm CMMG upper I will be using includes their BCG. So you are saying that it is ok to stay w/ the standad hammer included in any old LPK? If so, that would be awesome, no need to spend extra on a new hammer.

NSR500
05-27-2009, 10:48 AM
Yes, the ramped CMMG bolt is made that way to be used with the standard hammer. A ramped bolt 9mm system is easier on the standard hammer and will not do damage. The advantage to the ramped bolt is a 100% AR lower compatibility, so you don't have to dedicate a lower to just being 9mm, as long as you use a drop in mag block.

///D
05-27-2009, 10:49 AM
Yes, the ramped CMMG bolt is made that way to be used with the standard hammer. A ramped bolt 9mm system is easier on the standard hammer and will not do damage. The advantage to the ramped bolt is a 100% AR lower compatibility, so you don't have to dedicate a lower to just being 9mm, as long as you use a drop in mag block.

Awesome, thanks for the info.

NSR500
05-27-2009, 10:52 AM
Good luck with your build!