.308 vs 300 blackout
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Old 07-08-2012, 01:06 AM   #1
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Default .308 vs 300 blackout

So I am going to build a new rifle and thought at first just to build a regular ar with a 300BO barrel, but now I am wondering whether it would be better just to go .308 all the way. What are the Pros and Cons?

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Old 07-08-2012, 01:09 AM   #2
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Well first, do you want the AR-15 platform or AR-10A?

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Old 07-08-2012, 01:25 AM   #3
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Two entirely different animals.

The .300 Black Out is a wildcat from the 5.56mm case. You reload it by trimming somewhere between 1/4 to 1/3rd off the 5.56mm parent case. Bonus for the Black Out.

The .300 Black Out uses most all the same AR-15 parts including the mags, bolt and without changes to your gas system (caveat - as long as you don't have a SBR or finely tuned system to start with). Bonus for the Black Out.

The .308 is a very powerful cartridge, but it requires an AR-10 and all the gear. It is not AR-15 compatible.

.300 Black Out is expensive to buy. If you reload 5.56mm brass, you can shave a ton off that cost per round, but if you are not set up to reload, you are going to go broke shooting it.

Th .300 Black Out is really the most effective when it is suppressed. Not that it isn't a very good round, it's impressive and ballistically it's far superior to the 5.56mm.

The real benefit of the .300 Black is that with just a barrel change you can shoot it from any existing AR-15 and can up to a "factory" 220 grain round. That is IMPRESSIVE hitting power and 4 times that of the 55 grain 5.56mm

The .308 AR is much more prevalent. It's been around longer and it packs a serious punch with the ability to stretch the battlefield.

Of the two I would say the .308 is going to be more expensive to get into, but cheaper to shoot. The .300 is going to be cheaper to get into, but will be expensive to shoot and in the event of needing to get ammo for it, much-much harder if you are not set up to bang out 1,000 rounds in the garage on a weekday night for an upcoming weekend range session.

I dare you to build the .300 BO, get a quality suppressor and tell us all about the entire process.

JD

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Old 07-08-2012, 01:39 AM   #4
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300BLK is about 2/3 more expensive to shoot with commercial ammo (comparing XM193 vs. 115gr supersonic 300BLK ammo). The cost of ammo, in terms of cents per round...the 5.56 is in the low 30's, while the 300BLK is in the low 50's.

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Old 07-08-2012, 01:40 AM   #5
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Thanks yeah I agree it's the initial cost of the 308.

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Old 07-08-2012, 03:53 AM   #6
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Quote:
Originally Posted by GREGULON View Post
So I am going to build a new rifle and thought at first just to build a regular ar with a 300BO barrel, but now I am wondering whether it would be better just to go .308 all the way. What are the Pros and Cons?

What is the intended use of this weapon? There is a LOT of difference between a .300 BlackOut and a .308/7.62 in several ways. Yes they both can and do run the same bullets but the 300Blk will be 200 to 400 FPS slower. The AR platforms are very (size wise) different, the .308/7.62 being a longer cartridge by far. Costs are also higher for the .308/7.62 version.

So to the Pros and Cons.

300Blk first:

About the same cost to build as a comparable AR in .223/5.56.

All of the same hardware as the .223/5.56 with the exception of the barrel.

Hand-loads are cheaper. Brass is cut down from common .223/5.56 brass, primers are the same as .223/5.56, different powder from the .223/5.56 and generally less of it. Also different from the .308/7.62 and a lot less of it.

Less recoil.

Less velocity/energy and the range of use is limited by this. Don't plan on shooting a thousand yards in competition.

Utilizing sub-sonic loads, the use of a suppressor could actually be useful.

Limited but growing number of listed loadings.

And now the .308/7.62 version's Pros and Cons:

Greater energy, greater velocities, greater ranges. And the associated recoil and noise.

More expensive to build/buy.

Brass is more costly and a little more powder is used in loading.

Lots of loading data.

Ammunition is available most every place.


I hope this helped a little.

I don't have an AR built for the .308/7.62 round (oh, they are generically called AR-10s) but then I do have an M1A. Kind of hard for me to justify one.
I have several ARs in .223/5.56 and one in .300 BlackOut. Again, kind of hard for me to justify any more.
The 300Blk doesn't begin to replace it's skinny brother or it big brother. They all have a nitch that they fill, at least for me. And I have no interest in SBRs or Suppressors. This old fat guy likes to tote a light handy 16in AR type about in .30 cal. The likelihood of me running into a pig as I walk my NE ridge is slim, but I would like to pop one with my BlackOut.

It all comes down to what is the intended use of this weapon?

PS. The .300 BlackOut is no longer a 'wildcat' round. It has been accepted with a SAAMI standard.
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Old 07-08-2012, 08:45 AM   #7
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I just wonder if the Blackout ammo will become more common and easier to buy. I guess the .308 is not the right round to compare it too. The 7.62x39 is really the one.

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Old 07-08-2012, 09:45 AM   #8
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Quote:
Originally Posted by GREGULON View Post
I just wonder if the Blackout ammo will become more common and easier to buy. I guess the .308 is not the right round to compare it too. The 7.62x39 is really the one.
300BLK has been around much longer than I honestly know, but has gained a lot of popularity over the past couple years. Just about every major manufacturer has a 300BLK rifle in their lineup. There are already dozens of ammunition manufacturers cranking out super and sub ammo...a few big names and a lot of small outfits. The cheapest that I know of right now is the Remington/UMC 115gr. CTFB for just over $10 for a box of 20 rounds. 300BLK products will become more prevalent and as long as more and more companies jump on board the AAC BLACKOUT train, we should see pricing come down further.

LMT has one of the easiest platforms to switch between 5.56 and 300BLK. Their MRP line of rifles and uppers allow the end-user to switch barrels very quickly via their quick-change barrel locking bolt in their monolithic upper receiver. I received a small order of the LMT 300 Whisper/AAC BLACKOUT barrels last week and they sold out within hours. Templar Custom also makes a couple of rail systems that allow relatively quick barrel swaps by using their proprietary barrel nut. Their FastRail is a free float quad rail and their RaceRail is a free float top rail only handguard, yet gives the end-user the option to add rail sections anywhere along the 3, 6, and 9 o'clock positions.

You are correct that the 300BLK is more comparable to the AK's 7.62x39...300BLK is 7.62x35. The biggest problem with the AK round in the AR platform is the 7.62x39 round's taper does not allow it to feed reliably in an AR magazine. The 300BLK can be used reliably in standard 5.56mm magazines.
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Old 07-08-2012, 05:53 PM   #9
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Quote:
Originally Posted by GREGULON View Post
I just wonder if the Blackout ammo will become more common and easier to buy. I guess the .308 is not the right round to compare it too. The 7.62x39 is really the one.
Another beast to look at.

I will start with full disclosure. I don't like the AK and or any of the items associated with it and that includes the M43 round. This is personal with me and doesn't mean that there isn't many good qualities to that stuff, but not for me. Anything that me or mine was shot at with is not for me.

That said.

The 7.62X39 has a larger head, this equates to weakening an AR type/size bold. That's not a lot to be concerned with, everything is over-built to some extent. And the 7.62X39 is (exaggeration here) shaped like a wedge. This causes a lot of rearward thrust and adds a lot of stress on the bolt's lugs. Worry not, everything is over-built to some extent. But, add the two together and their could be a problem in a modified AR type/size bolt. I am only going on things I have read by several people that may or may not know what they are talking about. I have no idea and it has no effect on me, see above disclosure.
This case shape also adds to feeding problems with straight mags. I am sure that some/many can and will/have came up with a fix for this.

The weapon/s and what they eat. The attraction is well founded. A very strong, simple and functional action, dummy proof. The ammunition is currently cheap in price and in my opinion quality. Moving up to quality ammunition, the cost go up. I see no reason why accurate ammo could not be found/made. The current actions are not designed for tight tolerances (thus they shoot and shoot and shoot, no matter how much gunk comes their way) and this looseness is not going to benefit the weapon in accuracy. Oh, the actual bullets are not the same 7.62s we think of. A different but still correct method of measurement. They are .311 inches compared to .308 inches, the same general diameter as the 7.7 Jap and British 303 and that limits the number of production bullets available.

OK, the problems with an AR chambered in 7.62X39 set aside. The standard 7.62X39 is a 120 to 135 grain FMJ with a sharp tip, that is pushed at 1900 to 2400 FPS. Switching to better (not sanctioned by any Geneva Accords) bullets and we have a respectable loading. Not unlike the old faithful 30-30. The big plus in the magazine capacity. Oops, most States hunting regulations limit capacities, hmm.

A quick comparison with the .300 BlackOut in this same vain.
Trying to stay in the same bullet weight range. I load 125 grain OTM (I think them to be too expensive and have moved on to better, in my opinion, options) to a velocity of 2123 FPS average @ 10ft. And these are Open Tipped Match bullets. Very accurate, limited expansion and well on par with the 7.62X39. [Note: I prefer 110gr VMax running 2302 FPS average @ 10ft and 147gr FMJ Mil running 1988 FPS average @ 10ft. I think either of these kick @$$ over the 125gr OTM. And I will soon, if the heat wave ever breaks, move on to 150gr bonded core bullets, another over priced bullet in my opinion.]

So, my stance is set. As for you, go for it. You decide what you want to do. I will applaud your actions no matter what your course.
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Old 07-08-2012, 08:14 PM   #10
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Quote:
Originally Posted by GREGULON View Post
So I am going to build a new rifle and thought at first just to build a regular ar with a 300BO barrel, but now I am wondering whether it would be better just to go .308 all the way. What are the Pros and Cons?
Does the 300 blackout ballistically meet your requirements?
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