Besides the barrel, what else needs to be changed? Different bolt, carrier, .
Any good source (price) for barrel. Thinking about maybe using barrel that is as short as the ballistics of the round will allow. I have a short barreled rifle so the overall length is not an issue but what would be too short to get best performance. Plan on using suppressor is another reason short as reasonably feasible.

Thanks in advance for the info.

Eseaton

The barrel that is it.  Everything else is the same.

Barrel. That's it.

All other components are shared, including mags.

If you have a brake or a flash hider, you need to change it too. The 300 Blackout is a 5/8-24 thread, the .223/5.56 is a 1/2-28 thread.

Not necessarily.
My 300 BLK is 1/2 x 28.
Make sure you are using a .30 cal flash hider.

Dave N

Gas tube will likely have to be changed as well.  Most .300 barrels use shorter gas systems.

Most 300 Blackout barrels have pistol gas ports, so you'd probably need a gas block and gas tube as well.  And don't forget that the muzzle device will need to be a .30 caliber item - not only a .30 cal hole, but almost all the 300 Blackout barrels I've seen have a 5/8x24 (as opposed to the .223's 1/2x28).

Instead of saying "just the barrel needs to be changed," it would be better to say "the barrel assembly needs to be changed.

8" barrels are popular, as are 10.5s.  I have an 8" CMMG barrel that's nitrided, and I'm just waiting for the chance to load up some rounds to try it out.  CMMG and Aero Precision have decent prices on 300 Blackout barrels.

What about stiffer Recoil spring & H2 or H3 Buffer of heaver?

Thanks.
Good responses so far. This forum never let's me down.

Eseaton

 

I really wish I knew where and how this rumor got started.

Countless times people have posted a problem on 300blktalk.com where either they built one or had a gunsmith build one and when they give the parts break down they have either a heavier recoil spring or a heavier buffer.  Usually because they either claim they read it somewhere or their gunsmith told them it was needed.  My favorite lately is adding the pigtail gas tube.
AAC does recommend a H2 buffer and standard recoil spring with their short barrel but I have found it is  not needed.  maybe this is where it gets started and then grew from there.

What is even better is they usually start off the conversation like this.

" I did a bunch of reading and research and built this based on advice I saw here"

anyways.  Standard buffer and spring work great.

This......