A few years ago (Feb of 2011) I bought a CMMG pistol upper from an online retailer. It was advertised as a 7.5" 5.56 upper. I used it to finish my SBR and never had any issues with it.
I recently decided to convert the SBR to 300 BLK. I bought a CMMG 8" barrel for the conversion.
I wasn't sure if I would need a new gas block or not, but from what I could find online, the gas port location on the 5.56 barrel should have been the same size as the 300 BLK barrel, so the gas block should have worked.
I took the upper to a local place to swap out the barrels. They called to let me know that the gas block would not fit because the old barrel was a thinner profile than the new barrel. I had them order a new gas block from CMMG to complete the build.
When I got home with the upper and the old parts, I looked at the original barrel and could not find any markings right away to identify it. It doesn't look like pictures I've seen of CMMG pistol barrels online.
Did CMMG make pistol uppers with pencil barrels?
Here's a picture of mine:
Here's a picture I found online for a CMMG 7.3" barrel:
I just wanted to be sure of what it is I have here.
Thank you!