Your 14.5" is WAY more accurate?? Lol. You do know barrel length has nothing to do with accuracy and plays into velocity right? Any accuracy statements or opinions your making regarding barrel length come down to the specific barrels you were shooting, not their length..
I have a 10.3" Daniel Defense and a 10.5" WOA. Both are 5.56 1:7 barrels that shoot sub 0.5moa groups.
Here's a seating depth test from the Daniel Defense 10.3" barrel...
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Here's a 7x5 target I shot at 100yds from my 10.5" Rainier Ultramatch 300blk SBR...
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Yes, as I said, my 14.5" is WAY more accurate. You can laugh at me all you want, I am simply reporting my experience.
I have heard the "shorter barrels are just as accurate" argument god knows how many times! I understand the argument that a shorter barrel should be stiffer, and suffer less barrel whip, and thereby, in theory be slightly more accurate. That may be the case for some people, and your results are very impressive, but that has not been my experience. And I have my doubts that your experience is the rule rather than the exception. Also, I don't see how your posting groups out of your 300 blackout is valid in any way, its a different caliber, and an entirely different animal. Super impressive groups though.
Honestly, I don't think there is very much good data out there on this subject. I think this is because most people don't put much effort into shooting their 10.5/11.5's for groups. How many guys shoot their 10.5 for groups at 100 yds with a red dot off a wobbly bench? 2 moa? good 'nuff its a room-clearing gun, and their right. The percentage of folks that even want, or care that their 10.5 is sub-moa has got to be incredibly small. Somebody should build several guns with the same parts and barrel manufacturers in different barrel lengths, and then shoot for accuracy, preferably an awesome shooter, off of a solid bench, and with good optics.
At the end of the day, I don't know if my bad experience with short barreled AR's was due to length or barrel make. Nor do I have the money, or inclination to find out. As is clearly stated in my original post, the 14.5" barrel is by Battle Arms Development. The 10.5" and 11.5" were both stainless Noveske barrels. All three were tested with the same PST 2.5-10X32. All three were wearing Geiselle SD-E triggers. All three had SLR adjustable gas-blocks. the 10.5 and 11.5 were full Noveske builds. The 14.5 is mostly a Battle Arms development build. All three were put together by Impact Guns in Ogden, UT. I could not get the Noveske's to shoot better than 1.5-2.0 MOA with any kind of factory ammo. The BAD build regularly shoots .75 MOA and occasionally better with good Hornady and Black Hills match stuff. That's my experience posted for free on the inter-web. Take it or leave it.