.300 Blackout vs 5.56

[Pdvdh]

I like the 62 gr gold dot/fusion bullets for 223 hunting, they are bonded and retain more weight than most other bullets

My son just killed a Timber Wolf with a 64gr Nosler Bonded Solid Base. Heart shot from 50 yds.

 

[MudRunner2005]

8 twist will stabilize anything that is magazine fed. 8 twist will also let you shoot lightweight varmint bullets.

7 twist will cause some lightweight varmint bullets to come apart from centrifugal force. I have had 53g SMKs come apart in a 7 twist.

I have had an AR15 with everything from a 10.5" barrel to a custom 26" barrel. My personal preference is an 18" barrel that is not a bull barrel. Bull barrels add unneeded weight unless you are hunting prairie dogs where the barrel can heat up. But for most people a standard profile is perfectly fine without adding weight.

As far as 5.56 versus 223 there has been several studies done showing a far amount of 5.56 marked guns actually having 223 chambers. Shooting 5.56 in a 223 will not blow your gun up. It might show some pressure on the brass but even that isn't anything to worry about. I have an AD with a 223 match chamber and it has only had 5.56 fired out of it without an issues at all. If shooting 5.56 in 223 chambers caused the gun to blow up we would hear about it a lot more.

And while you are building it install an adjustable has block. Most ARs are over gassed so the manufacturers do not have to do warranty work on a gun that won't fire cheap, underpowered ammunition. With an adjustable has block you can tune the gun and reduce recoil, reduce has in the face, reduce crud in the receiver and make the gun more reliable. With an adjustable has block that is tuned and a quality muzzle brake an AR will Feel like a 22.

That was most likely a defective bullet or bad batch. An extra 1" of twist at 223 velocities is not going to cause that much of an issue. I shoot 55 grain bullets through 2 different 7" twist barrels and have never had that issue in thousands of rounds.

Please show me links to these studies you talk about... The cartridge chamber dimensions are the exact same...HOWEVER, a 5.56 NATO spec chamber does in-fact have a longer throat dimension and different leade angle than a commercial .223 Remington chamber...Thus allowing you to shoot .223 Rem in a 5.56 NATO chamber, but can cause pressure issues if you shoot 5.56 NATO ammo in a .223 Rem chamber. This is fact, and not up for debate. If you don't believe me, then I suggest arguing with the people who designed and spec'd the differences between the 2, and tell them you think they're wrong.

Nobody said your gun would blow up, but it can... And it can cause problems. Just like shooting commercial .308 Win ammo in a 7.62x51 NATO chamber CAN cause issues because commercial .308 Win brass is thinner than 7.62x51 NATO brass, and the excess headspace in the NATO chamber can cause stretching that can cause a case rupture.

Also, as for the adjustable gas block, it is far from necessary. I've shot both, and all of mine have high-quality standard non-adjustable gas blocks, and no ill-affects, even shooting cheap steel-cased ammo, the rifles are just as clean, and are just as reliable as all the rifles I've shot and messed with that have adjustable gas blocks. If you want the cleanest and most-reliable setup, get a self-regulating gas piston system for your AR.

Gas blocks won't reduce your recoil, but they can change the bolt speed by adjusting the amount of gas that operates it, which changes the felt impulse, which can trick you into thinking that the recoil is more or less than before. Also, they don't make your gun any less or more reliable. That's just a manufacturer ploy to get you to buy into what they're selling. It's the exact same gas block as a non-adjustable gas block, it just allows you to adjust the amount of gas passing through the tube. You are, however, correct that they reduce gas in your face when shooting suppressed.

 

[MudRunner2005]

Barrel length... Sorry

Are you wanting more of a varmint/target type setup, or something more portable and lightweight?

 

[Vortex!]

I have a 5.56 and I was going to get a 300 blackout but then I found out about 6.5 Grendel and decided that it was better than either of the two mentioned. Just my .02.

 

[MudRunner2005]

I have a 5.56 and I was going to get a 300 blackout but then I found out about 6.5 Grendel and decided that it was better than either of the two mentioned. Just my .02.

I have all 3 cartridges mentioned, and for hunting, you're correct... The 6.5 Grendel all day long. But for plinking, the 5.56 is the most cost-effective, and for a suppressed or SBR setup, the .300 BLK takes the cake. They all have their place in the food chain.

 

[dolomite_supafly]

Firing 5.56 in a 223 will increase pressures but if it caused any sort of damage we would hear about it every single day, we don't. It isn't going to blow your gun up unless it has other issues.

There was a website that took SAAMI spec 5.56 and 223 gauges to a public range. They tested almost all of the 5.56 marked guns present and more than 25% had 223 chambers. I am trying to find it but I remember reading about it.

I have had several other shooters report the same thing, 53 SMK above 3,300 fps in a 7 twist will sling the jackets off. Of course every gun is different but when I posted about it when it happened ~10 years ago I was not the only who had experienced it. It was going ~3,380 fps out of a 26" barrel that was 7 twist. Standard 55 grain FMJ bullets are very different than SMKs. SMKs have a much thinner jacket so the FMJ will not loose it's jacket from centrifugal force like an ALL with a thinner jacket.

I will say that my 223 chambers AR shoots better than most of the 5.56 chambered guns I have owned. But for my purposes the difference doesn't matter because I am no longer a paper puncher and shoot steel now.

 

[Elkeater]

So after all the info on here reads I decided two things. First I bought a Wilson combat 16" 1:8 twist barrel in 5.56. Second the AR build rabbit hole is a very deep dark place. Fun and interesting but deep and dark. It might keep me sane while I recover from surgery instead of chasing critters this fall.

 

[Ckgworks]

[QUOTE="Elkeater, post: 1475577, member: 103670"Second the AR build rabbit hole is a very deep dark place[/QUOTE]

Once you build a couple, they seem to multiple like rabbits as well.....

 

[dolomite_supafly]

When you have spare parts they tend to turn into complete guns. I built a gun so I would not waist a few parts.

 

[stwcattle]

I have owned/own 5.56, 6.8SPC, 6.5 creed, 6 creed, and 6.5 Grendel.

Grendel all day long for one rifle, all around use.

If planning a lot of rounds down range on paper and steel, .223/5.56 probably makes more sense. But if wanting to shoot longer distance with hunting capability, 6.5 Grendel would be my choice/recommendation.

 

[Pdvdh]

First I bought a Wilson combat 16" 1:8 twist barrel in 5.56.

I say Git'r Done!

 

[Lasiter]

No mention of 7.62 x 39?

 

[Chevy Miles]

So I finally bought a stripped AR lower and decided to build an AR. I've never owned an AR of any kind but always wanted one. Anyways what I'm curious about is what caliber to go with. For simplicity sake I'm looking at either 5.56 or .300 blackout since they both use the same parts except the barrel. Right? So what's the pluses and minuses of these two cartridges?

Any input is appreciated. Thanks all

No, the 300Blk is a 30 cal barrel...the .223 cartridge requires a .223 barrel!

 

[Deleted member 48126]

I would just get a .300BO upper and a .223/5.56 upper and swap them out whenever you want. The market is absolutely flooded with ARs. I got a rock river arms AR upper in .300BO with a Midwest industries rail for $300!!!