Kinda depends on what you want to use it for.     It is better suited in the subsonic suppressed role over supersonic.  Hopefully ammo will become more plentiful in the near future.  The Blackout is no slouch but it's also not the be all end all round either.

Here is a link to a ballistics trajectory chart comparing a Blackout round to M855 and MK262.   The Blackout is always compared to M855 which is only a 62 gr bullet.  However the MK262 is a 77 gr 5.56 loaded round.   The Blackout round being compared to is the Best .300 round available....the Barnes 110 gr Black tip.

ShootersCalculator

Thanks for the help.  

I'm mainly looking for using it as a short (16in barrel), light weight rifle to hunt with.  Most shots less than 100yds.   Kinda like a brush gun, for deer and hogs.   I use my bolt gun for more open areas.   Maybe suppress it later on.   It seems like a fairly easy round to reload for,  especially since I still have some 223 brass.

I'm like ar platform,   Kinda regret selling mine during the panic.  I don't know a lot about the round, but seems like it would fit the bill for me.

If you notice in the ballistic chart I linked too even the best round is no match for the heavier 5.56 loads.  In the supersonic realm.  Even though the .300 is always perceived as "better" than the 5.56 as you can see it simply depends on which 5.56 rounds you're comparing it too.  Lighter rounds YES!   Heavier loads absolutely NOT!  Of course this is just comparing ballistics and energy.   The heavier 5.56 rounds at this point are MUCH more available at the moment.

Where the .300 is impressive is in suppressed subsonic shooting.  Here a fatter bullet it always gonna win over a smaller round due to pure physics.  And remember when comparing subsonic rounds were talking about limited velocity.  Roughly 1100 fps or less.   So it's better to hit something with a .308 sized round over a .224 sized round because velocity is the same.

Something you also may want to consider if choosing the .223 case is a new round called the .277 Wolverine.  The .277 Wolvy uses a .223 as a parent case like the .300 BO however instead of using .308 bullets it uses .277 bullets.   The .277 rounds developed for the 6.8 SPC.  The developer is still waiting for his first shipment of barrels to sell.   The advantage is higher velocities than the BO.  Which of course results in better ballistics than the BO.  Just something to consider.   At this point it is not a SAAMId round and is a Wildcat.    But has quite a following on the 68forums.

I know the .300 BO has developed something of a fan base but much of it is based on hype over actual performance which in turn ends up being more like fanboi.  Again not to take away from the round itself.  It is still a quite good round.   The chart I linked to above was using the best round developed for the .300.  That tops out around 2425 fps.  All the other rounds are simply slower or less effective bullet.   The Barnes 110 gr TTSX(Black Tip) bullet was designed for the .300 BO and will open down to 1300 fps.  That helps give it a little more effective hunting range.  The BO has been compared to the 7.62 x 39(AK) or even a 30-30 Winchester.  Neither round is exactly the top of the ballistics charts.  However they both will kill and kill well.

Some other calibers you might also want to consider is the 6.8 SPC as well as the 6.5 Grendel.   The 6.8 is arguably the best all around cartridge for the AR-15 platform.

But back to the .300.  One of the arguments for it is it is cheap to convert because it uses all the standard AR-15 parts but the barrel.  In your case you're not converting anything so really nothing to save.   This saving is always pushed for those wanting to convert to the .300 from a 5.56.  However most don't simply change calibers but add the .300 to what they already have.  With this you can use the same mags.   But does anyone actually swap BCGs back and forth other than for short periods while waiting for new parts?  Again so where's the savings?

Also a big thing for the .300 is which gas system to use.   If you ever plan on shooting subs you need a pistol gas system.  So basically you have two choices.....Carbine length or pistol length.  It you think you "might" be shooting subs go ahead and get the pistol gas because it will shoot supers just fine.

My FAL can beat up your blackout!

...in more ways than one.  Damned heavy pigs.



 

Good stuff.  Thanks for that link & comments, Bama.

Thanks for the info,  good info there.  

Well,  I pulled the trigger on an upper in 300 blk.    I took your advice and got the pistol length gas system,  16in barrel.  

What buffer spring/weight should I use?   Or does it matter.  I've heard some folks run into cycling issues due to incorrect buffer spring/weight.

Again,  thanks again for your help.