Do I really want a 10.3" upper vs. another 11.5"

[slowrx]

I have a few 11.5's and also had a two 10.3's. I found myself shooting the 11.5's almost exclusively. I eventually sold off the 10.3 uppers and replaced them with more 11.5's . It was more personal preference than anything performance related. I like the little bit of extra rail space for lights/lasers and my go to can is a mini so the OAL added was insignificant. If you are curious try it, you can always sell it off or re barrel it....or go with what you know and like.

[HMsailor]

10.3 supressor ready

[kirkland]

Do you really want a 10.3 upper? Only you can answer that. I would argue that you already have two 11.5's so why not add a 10.3?

[Bullz]

I just built a 10.3" upper with a brand new DD barrel assembly with FSB. DD Barrel & FSB, BCM everything else. I used a standard round handguard, no rails. Gas port measured right around .070 (my gauge actually read .068 but I doubt that's correct).

Just got back from the range where I ran 150 rounds through it to break it in. Shot some groups at 50 yards to zero, then moved out to 150 and 230 yards on steel silhouettes. Some slow fire, some fast, one mag dump. All Federal XM193. No issues whatsoever, which kind of surprised me. It's also very, very soft shooting, which also surprised me. Consistent 4 o'clock ejection pattern with an H1 buffer.

I wanted the shortest 5.56 on carbine gas and went with the DD barrel figuring they'd know what they were doing on something that short. One range session and I'm in love with it.

[Joelski]

I say go 10.3"/10.5" in .300 BLK and have all the good and none of the potential problems 5.56 does. My gun runs fine with a regular carb buffer with, and without a suppressor.