View Full Version : 8.5 5.56
MrLegalAce777
04-07-20, 15:11
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
04-07-20, 15:42
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.
Yes, the super shorty 556 barrels are incredibly loud, even outdoors.
MrLegalAce777
04-07-20, 15:58
Even from a piston gun? I have some earpro that sits on my hd guns
ViniVidivici
04-07-20, 16:02
Piston or DI is irrelevant to the noise and blast at the muzzle.
Even from a piston gun? I have some earpro that sits on my hd guns
Yes, insanely loud.
MrLegalAce777
04-07-20, 16:02
Okay but wouldn't ear pro mitigated that?
A suppressor would be way more helpful. I would double up and wear plugs and earpro on a gun like that even outdoors.
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
04-07-20, 20:14
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.
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.
IMO I think this is where 300 blackout come into play.
Is the terminal ballistics really going to be a game changer at that length vs 9mm?
The noise is incredible, in a bad way. Linear comps might help, but inside a house, it wont matter.
300blk or 9mm at that length in my opinion, and train.
If something happens, you wont die because you picked the wrong gun or caliber.
Get the best gun for the job, train, buy decent ammo.
Why do you need an 8” barrel? As a side note, I find when you get really short, controlling recoil is more difficult. Not saying you cant run a short gun well, but I prefer 11” min for rifles.
ViniVidivici
04-07-20, 23:09
Yeah, for me 11.5 is the sweet spot for a shorty AR in 5.56.
I agree, less than that is .300 BO land.
Specifically for the Bren 2 you mentioned, if you look at what has been fielded, the French GIGN selected the Bren 2 with a 9" barrel, but picked the 7.62x39 caliber. Which I think is a much better choice if you are going that short.
My memory may be faulty, but I think they switched to the Bren 2 from the G36C 5.56 which also has very short barrel around 9" or so.
bamashooter
04-08-20, 14:35
My 8.5" (5.56) is on top in the pic. Though noticeably louder than a 16" carbine, I don't find it that much louder. There's very little difference using an A2 flash hider or linear comp. I've fired it several times outdoors and inside a poultry-house. I like the maneuverability of it and have little concern for hearing issues if it's needed to pop someone. 99% chance I'd never use it indoors for defensive purposes.
https://i.imgur.com/gFQBNVN.jpg
Depending on your ammo, you could run out of the expansion envolope relatively quickly. And some rounds may not stabilize out of such a short barrel. There’s a reason why people who fight in close quarters don’t use such short barrels for 5.56.
For home defense, were another 3" of length is a non-factor, 10.5-11.5" is the answer. Only reason to go shorter than that is specialized concealment requirements (bag, backpack, etc) IMO.
As I have no interest in a 300BLK build, I use my Scorpion-K Pistol build 5" 9MM or my SCAR 16 SBR 10.5", but only if it has to go into a bag.
For HD 11.5 Suppressed 5.56 SBR.
There’s a good thread on P-F about the same exact topic, and there was some evidence that specific grains of gold dots will still be inside of the threshold with normal indoor ranges from an 8” barrel. That being said, I’m of the belief that a MK18 is the shortest worth going in a 5.56 and it’s compact enough that unless there is a definite need, it’s a good balance.
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MK18 is the shortest worth going in a 5.56 and it’s compact enough that unless there is a definite need, it’s a good balance.
100%! There is a reason that SOCOM uses 300 blackout below 10".
titsonritz
04-08-20, 16:23
This is precisely what 300 BO was designed for.
knownothing
04-09-20, 07:50
I agree. I bought the 6.75 5.56 Barrel for two reasons; it was a good deal with a sale BRT was running and ammo commonality. I don't own a 300 blk right now and will be holding off on one for a while until I can get enough reloading components in place to make it economically viable for me to shoot in higher volumes. But yes I agree, a 300 blk is definitely a better choice in terms of terminal effects with such a short barrel.
In my opinion if your going to go below 10" on 556 you should own a chronograph and find ammo that will do what it is supposed to do at the velocities you are getting. If you are not doing that you are completely flying blind and good luck.
I agree. I bought the 6.75 5.56 Barrel for two reasons; it was a good deal with a sale BRT was running and ammo commonality. I don't own a 300 blk right now and will be holding off on one for a while until I can get enough reloading components in place to make it economically viable for me to shoot in higher volumes. But yes I agree, a 300 blk is definitely a better choice in terms of terminal effects with such a short barrel.
If you had not bought that barrel you would be that much closer to your .300 goals.
knownothing
04-09-20, 21:17
If you had not bought that barrel you would be that much closer to your .300 goals.
It's been a fun project seeing what the lower limits of .223 effectiveness look like. My .300 goals are pretty low priority.
daddyusmaximus
04-10-20, 08:28
These small package deals are exactly what the .300 BO is for... as has been mentioned... I know, I know.
I put an 11.3" .300 BO together for myself as a HD gun, but though I love it, It doesn't get used much because it's chosen duty ammo, (110 gr Barnes VorTX) is expensive, and hard to get. After training with my 10.3" 5.56 so much, I just started stocking up on better 5.56 rounds, that are much more cost effective, and easier to find. (as long as there's no pandemic panic buying going on)
That said, I think I wouldn't go any shorter than 10.3" or 10.5" for the 5.56. From there to 11.5 or 12.5 is the sweet spot. They are where you want to be, and the only real limiting factor is how small it needs to pack up in for travel. I've gained a lot of weight since I got blowed up and retired, so I'm about 280 now, but I can still move around with my 10.3", and 11.3" guns pretty well in my home. I can even use them from vehicles. There's really no need to go down into the 7 or 8 inch realm unless you're in the "it looks cool" category... You're just making for a smaller handrail, and a louder gun, that shoots slower bullets.
Need a small package to travel? Get a Law Tactical folder for a 10.3" gun.
These small package deals are exactly what the .300 BO is for... as has been mentioned... I know, I know.
I put an 11.3" .300 BO together for myself as a HD gun, but though I love it, It doesn't get used much because it's chosen duty ammo, (110 gr Barnes VorTX) is expensive, and hard to get. After training with my 10.3" 5.56 so much, I just started stocking up on better 5.56 rounds, that are much more cost effective, and easier to find. (as long as there's no pandemic panic buying going on)
That said, I think I wouldn't go any shorter than 10.3" or 10.5" for the 5.56. From there to 11.5 or 12.5 is the sweet spot. They are where you want to be, and the only real limiting factor is how small it needs to pack up in for travel. I've gained a lot of weight since I got blowed up and retired, so I'm about 280 now, but I can still move around with my 10.3", and 11.3" guns pretty well in my home. I can even use them from vehicles. There's really no need to go down into the 7 or 8 inch realm unless you're in the "it looks cool" category... You're just making for a smaller handrail, and a louder gun, that shoots slower bullets.
Need a small package to travel? Get a Law Tactical folder for a 10.3" gun.
You can setup a folding brace on an 11" Bren as well.
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