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Discussion Starter · #1 ·
I'm on the waiting list for the 300 Blk out 9" barrel for my MCX. But after seeing some of these penetration videos the 5.56 actually out performs. (But 300 still carries the punch)
So now I'm debating going with the short 5.56 barrel for my SBR.
I understand that the bread and butter for the 300 is sound suppressed with a can. The cost/availability also plays a factor.
Now I'm debating.....thoughts!?
 

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300 blackout for the win. I guess it really depends on what you are using the gun for though. I cut my 16 inch MCX 300 blackout barrel down to 10.5 inches and it works great.
 

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It's a good question!! Am on the MCX 9" 300Blk kit list too.

My 1st SBR is a 10" 516 though. As you mention, 223/5.56 is an effective round. So, this gun serves as our home defense rifle.

A BIG plus for 5.56 is the ammo is MUCH cheaper, and I've greatly enjoyed this 516. If we could have only 1 SBR, this is still my pick.



Since our SBR is setup for home defense, we're running it suppressed - Am interested in 300Blk, because it's very quiet suppressed with sub-sonic ammo, and offers a lot of versatility with the broad range of available loads.

We'll probably always shoot the 516 more, given the ammo is so much cheaper. But, am also looking forward to the MCX 300Blk kit as potentially an even more effective home defense SBR.

Cheers
 

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I'm on the waiting list for the 300 Blk out 9" barrel for my MCX. But after seeing some of these penetration videos the 5.56 actually out performs. (But 300 still carries the punch)
So now I'm debating going with the short 5.56 barrel for my SBR.
I understand that the bread and butter for the 300 is sound suppressed with a can. The cost/availability also plays a factor.
Now I'm debating.....thoughts!?
Look at it from a bore diameter/case capacity standpoint! Also you need to think "outside the box"! As I've stated here before, when you consider factory ammunition, they have to manufacture ammunition for sale to the general public that will be safe for the "longest" commercially available barrel. I think the 300 would be more efficient in the shorter barrel, and burn "less" powder outside of the barrel.
 

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Discussion Starter · #6 ·
Called Sig Cs today to see if the 11.5" 5.56 barrel was available....in sure you guys can guess the answer.
So looks like I'll be waiting either way.
They did tell me today that the 300 blk out has been approved to start production next month and should be shipping before summer. We shall see, not holding my breath.
 
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If I read this correctly the 300 BO burns up all the powder in a 9-10 inch barrel thus giving you the max in your SBR\pistol - which makes this an excellent choice for that application. You may lose some vel\energy with a SBR in 556 since I think you need more barrel. In addition 300 BO spans from a 110 grain bullet to 220 grain which is really nice as well.

One down side of the 300 BO is ammo is not as cheap or readily available as 556.

Good luck.
 

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.300blk gives full powder burn and full velocity in a nine inch barrel.
5.56 does not. Minimum length most would recommend would be 11.5 for 5.56.
10.5 works well but there are plenty of tests showing that just that extra one inch results in considerable more 'dwell time' for the powder to burn and the bullet to develop energy. Results in much less muzzle blast/flash.

9 inch barrel? .300blk for the win.
 

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The ISR I just bought has a 9" barrel and the suppressor is stamped to it to make the 16" limit. If you get into a 300 blk you should really look into reloading.
 
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