8.5 5.56

[MrLegalAce777]

I am thinking about trading my 4.5 mpx-k for a cz bren 2 in 5.56 with the 8.5" barrel. My question is for home defense cqb is a 8.5" 5.56 better than a 4.5 9mm?

[ruckusjuice]

Better in what way? Terminal ballistics wise, definitely. There are several 5.56/.223 loads that still leave the muzzle with enough velocity to properly expand even out of an 8.5” barrel and maintain the necessary velocity at CQB distances. I think Speer Gold Dot .223 needs to be over 1700 or 1800 fps to expand properly. Are you planning to suppress it? An I suppressed 8.5” 5.56 going off indoors will really suck for everyone in the room, including you and your family members.

[Clint]

Yes, the super shorty 556 barrels are incredibly loud, even outdoors.

[MrLegalAce777]

Even from a piston gun? I have some earpro that sits on my hd guns

[ViniVidivici]

Piston or DI is irrelevant to the noise and blast at the muzzle.

[themonk]

Even from a piston gun? I have some earpro that sits on my hd guns

Yes, insanely loud.

[MrLegalAce777]

Okay but wouldn't ear pro mitigated that?

[themonk]

A suppressor would be way more helpful. I would double up and wear plugs and earpro on a gun like that even outdoors.

[jsbhike]

Yes, the super shorty 556 barrels are incredibly loud, even outdoors.

Played around with an 11.5" + A2 versus an 8.5" with a blast diverting muzzle device (not one of yours) that was roughly as long as the 11.5 overall and it was night and the 11.5" was noticeably less loud as the shooter or from any other position.

While noticeable while wearing ear protection, I don't know if there is any significant change in unprotected hearing damage between any barrel length/cartridge combination in the ranges getting discussed here. My assumption is the auditory version of falling 40' versus 50'.

[knownothing]

I purchased a 6.75" PDW Barrel from Clint and went with one of his covert comps to go with it. So far, the pistol I assembled has surprised me in terms of loudness/blast from the shooter's perspective, as in it hasn't been what I thought it would be. Standing to the back left of my buddy shooting the pistol, I'd say it was less annoying than a surefire or a JP break. So far the pistol has chrono'ed factory 62 grain Speer Gold Dots at 1880 fps at the muzzle, and I am working up a load for 62 gr reloads at 5.56 velocities so I can expand the expansion threshold over further distances.

Saying all of that to say this, based off my personal experience with a short barreled 5.56 firearm, the muzzle device plays a large role in how negatively the shooter is affected, and ammo choice is extremely important given the reduced velocities you are working with. This firearm (My 6.75) isn't my 1st choice for home defense due to the concussive nature I think I would experience indoors, but I would rather use a short barreled 5.56 with the right load over a short barreled pcc to defend myself within my home.