Silly question: which 30 cal for my next AR? 300BLK, 308 or 7.62x39?

After limiting myself to 223, 308 and 6.5CM in my rifles for many years, I'm at a crossroads for my next rifle. I already have .223 in 11.5", 14.5" and 16" ARs as well as a 308 LMT with 18" barrel and a 6.5CM 24" bolt gun. I'm trying to decide between these three calibers for no particular reason:

1. 9" 300BLK
2. 11.5" 7.62x39
3. 13" 308

The 300BLK, of course, brings subsonics to the table. However, although I have a 30 cal suppressor, my local range(s) always have other shooters that are unsuppressed. The 7.62x39 is cheapest to shoot of the three and 308 is the only one of the three that I already have ammo for. The idea of a 308 SBR is also tempting for some strange reason. Any of these three could be used for home defense, hog hunting, range days, etc. I don't have a specific use-case for them, but just thought I'd ask for some opinions and possibly have a discussion.

I've noticed prices on 762x39 going up. It's not the budget panacea it used to be.

I'm a huge fan of 300blk in really short barrels.

The SCAR 17 SBR is pretty sick though, especially with the recent updates.


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I did some searching online and it looks like 9” 300BLK will get about 2100-2200 fps with commercial 110gr loads. While a 13” .308 can get about 2400 fps with most commercial 168gr, 175gr and M80. My 18” .308 gets only 200-250 fps more. I don’t reload, so no custom hand loads for me.

Maybe I’m looking at it the wrong way? 300BLK strength seems to be subsonic close-range and 13” 308 brings mid-range punch. Which would be more satisfying if I already have 11.5” .223 and 18” .308?

I’ve never been an AK guy, so anything 7.62x39 will be a novelty item. It may not be in the running for long.

Maybe I'm just getting older, but unless the 308 is a heavy gun, it's not fun to shoot at all. 300 is too niche for me, and 762X39 is home in the AK. So I vote for 5.56mm!!! :cool:

And I thought maybe I was getting older because my LMT with 18” stainless barrel, 3-15x scope, bipod and suppressor is getting a bit heavy for me!

If you don't reload, subsonic Blackout in commercial loads is hit or miss whether or not it stays subsonic. It really shines when you can roll your own and create a load tailored to your rifle. This is just personal preference (everything is) but instead of a shorty 308, I would do a short 6.5 Grendel. You didn't say whether you hunt or not, but a 12.5" barrelled Grendel is a treat to carry and still packs plenty of wallup. You can use your 30 cal suppressor on it too. I will grant you that ammo is harder to find for it than a 308 but being the smaller AR15 frame a comparable sized rifle in Grendel is going to be lighter than a 308.

308 would be my favorite


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.308, but I might be biased. I refer to .308 Win as "God's cartridge" and have been told I hold the cartridge in such high regard, I'm not just a fan, I'm a member of a cult. Fair enough, but .308 still gets my vote.

9in 300 Blackout gets my vote. second pick with be the 308, but seems like 13 inches would not be much fun to shoot.

Might just be me, but I see 300BLK or x39 as being minor variations of a 5 56 gun while .308 is a more significant step. Sorta like engine options in an F150 vs making the jump to a 3/4 ton.

You gotta decide for yourself how far outside of your current box you want to go. What is the intended use that is driving you to 30 cal? Is it is just to have something different? What do you expect the gun to do better than a 5.56? You seem not to have defined answers to these questions.

In my case I went from multiple 5 56 ARs, added .308, then 9mm and .22lr.. I have yet to add 300BLK and I have AKs in the x39 flavors but not ARs. I also have multiple other guns in a spectrum of loadings. My ammo logistics are way more complicated than yours.

Though I have not followed your path of stocking limited cartridge types I do find merit to that philosophy. Were I in your shoes I would consider adding cartridges to the mix only if you feel the need to fill a specific role. I seriously consider myself to have an overly complicated "logistical chain". I stock 5 pistol calibers, 7 rifle calibers, plus .22lr and 12 Gauge. Your way is better.

Since there's no particular reason for the caliber, then you shouldn't need a particular reason to make the choice. Write each caliber name onto a small piece of paper and crumple them up. Walk to your closest neighbor's house and ask them to choose one.

I have no desire for any of the options you're considering.

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Originally Posted by utahjeepr

Might just be me, but I see 300BLK or x39 as being minor variations of a 5 56 gun while .308 is a more significant step. Sorta like engine options in an F150 vs making the jump to a 3/4 ton.

You gotta decide for yourself how far outside of your current box you want to go. What is the intended use that is driving you to 30 cal? Is it is just to have something different? What do you expect the gun to do better than a 5.56? You seem not to have defined answers to these questions.

In my case I went from multiple 5 56 ARs, added .308, then 9mm and .22lr.. I have yet to add 300BLK and I have AKs in the x39 flavors but not ARs. I also have multiple other guns in a spectrum of loadings. My ammo logistics are way more complicated than yours.

Though I have not followed your path of stocking limited cartridge types I do find merit to that philosophy. Were I in your shoes I would consider adding cartridges to the mix only if you feel the need to fill a specific role. I seriously consider myself to have an overly complicated "logistical chain". I stock 5 pistol calibers, 7 rifle calibers, plus .22lr and 12 Gauge. Your way is better.

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Thanks for sharing your thoughts. I was able to ride out the Biden/Covid ammo shortage and even sell some 9mm and .223. I definitely realized the benefits of streamlined inventory in limited calibers. In reality, I still multiple types of cartridges for each caliber. For self-defense or home-defense, 9mm and .223 has all aspects covered for me. I’m not an avid hunter, so the .308 LMT was for shooting to the 800-yard max distance at my local range. Then I took a long-range class on a windy day and got frustrated with .308 from 600-1200 yards while other students shooting 6.5CM had a much easier time. I borrowed one of their rifles and was able to make first-round hits all the way to 1000.

As a recreational shooter, maybe I’m wondering if I have any gaps in my set of “clubs” for shooting. I don’t have any visions of an EDC backpack gun or truck gun or nightvision to defend my suburban house. The easiest thing for me to do may be to swap a 13.5” lightweight barrel in my LMT but I haven’t found any KeyMo mount can bring it to 16” so I’d have to Form 1 the LMT. Or maybe it’s just a temporary itch that’ll pass.

I bought a 10 inch PSA KS47 pistol along with a KS47 16" upper. Excellent shooting guns. I already have a bolt action .308 with 22-inch barrel for hunting and a few AR of varying legnths. Loaded up with relatively cheap and effective PPU 123g PSP, the KS47's are great truck/camping guns/HD if ever needed for just about any situation

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Originally Posted by crosseyedshooter

After limiting myself to 223, 308 and 6.5CM in my rifles for many years, I'm at a crossroads for my next rifle. I already have .223 in 11.5", 14.5" and 16" ARs as well as a 308 LMT with 18" barrel and a 6.5CM 24" bolt gun. I'm trying to decide between these three calibers for no particular reason:

1. 9" 300BLK
2. 11.5" 7.62x39
3. 13" 308

The 300BLK, of course, brings subsonics to the table. However, although I have a 30 cal suppressor, my local range(s) always have other shooters that are unsuppressed. The 7.62x39 is cheapest to shoot of the three and 308 is the only one of the three that I already have ammo for. The idea of a 308 SBR is also tempting for some strange reason. Any of these three could be used for home defense, hog hunting, range days, etc. I don't have a specific use-case for them, but just thought I'd ask for some opinions and possibly have a discussion.

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I wouldn't think a 13" 308 would be very fun... handy, yes.. but the muzzle blast would be crazy.

As for the 300BLK a 9" has a place for me, and just buying a Upper would be the easy button.

The 7.62x39 in 11.5"... now that would be something that would interest me , especially if it was a "AR" lower that would accept AK mags.

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Originally Posted by bfoosh006

I wouldn't think a 13" 308 would be very fun... handy, yes.. but the muzzle blast would be crazy.

As for the 300BLK a 9" has a place for me, and just buying a Upper would be the easy button.

The 7.62x39 in 11.5"... now that would be something that would interest me , especially if it was a "AR" lower that would accept AK mags.

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Chris Bartocci (sp?) did a review of the PSA KS47 and gave it high marks.

But without having true bolt hold open mags I would think a side charger would be better.

Supposedly the 28rd duramags are extremely reliable.


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I love Chris B’s stuff about the AR. I have purchased multiple books by him. But I really don’t trust his reviews of specific guns. Also, I found his conversion to Sig from Glock bemusing after he railed about the selection a couple years ago.

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Originally Posted by JediGuy

I love Chris B’s stuff about the AR. I have purchased multiple books by him. But I really don’t trust his reviews of specific guns. Also, I found his conversion to Sig from Glock bemusing after he railed about the selection a couple years ago.

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Yeah, his rant about the MHS was pretty epic.


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Originally Posted by mig1nc

Yeah, his rant about the MHS was pretty epic.


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Love the guy, and I appreciate it is hard to accumulate a social media following. But I’d bet a dollar you can pick up on the “I’m doing this review for the views and really don’t like this crap but will say it’s OK because I kinda have to.” There were like two videos where it almost felt like he was sulking while doing the review.

Again, I love his analytical stuff, the Caracal discussion, Black Rifle II, his armorers assembly/disassembly manual, etc etc. But just like I don’t go to an imam for a sermon about Jesus…

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Originally Posted by bfoosh006

The 7.62x39 in 11.5"... now that would be something that would interest me , especially if it was a "AR" lower that would accept AK mags.

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I spent a considerable amount of time building a 16 inch X39 that runs and eats everything. Then I replicated the process on an 11.5 (stamp is in process.) Then bolted on a Razor 7.62. It's one of my most favorite guns by far. No AK mags but don't feel the need with Duramags run perfectly. But I also don't own an AK so no stash of AK mags lying about.

Double tap

If you don't have a dedicated suppressed home defense setup, then a 7-9" 300 blackout is a nice addition to your toolkit. Just do a little home defense scenario larping when the wife and kids aren't home and you'll see how much of a difference it makes to navigate the corners and spaces in your house with a shorter barrel and suppressor.

Ex: My 8" 300 blackout with suppressor is still shorter than my 13.9 P&W 16" carbine by over 1.5" without a suppressor on it.

Sure, there is the MK-18 as a solution. But 5.56 gets real gassy at shorter barrel lengths and you'll need to tune your buffer weight, spring, and preferably your gas port.


13" 308 is cool, but what's the real application scenario there? Is it going to be a hard-hitting battle rifle that brings more oompf than 5.56 in the same range territory 5.56 normally covers?

I wish we saw more manufacturers doing 13.9 or 14.5 barrels in 308 expressly meant for pin and weld. I freaking love the length savings on my 5.56 with a 13.9 barrel.

I would go .300 blackout in a really short barrel. I have one with a 6” barrel and Maxim PDW stock. It’s a lot of fun to shoot. My .30 can for it is still in jail, so I haven’t been able to shoot it suppressed yet.

I had a .308 SBR (HK51) years back and it was a completely different beast. Huge fire balls and muzzle blast. I sold it and would never go that route again.

I've got shorty 300 BO and x39 uppers. The BO is just a subsonic range toy (for me, nobody get your feelings hurt). The x39 is just a blaster, but is so cheap to shoot....
My 12.5" 6.8 SPC is my hunting rig.
A short .308 seems fun, but expensive for fun.

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