[greg_r]

No, not firearm. Cartridge. Talking AR=15 here. I can keep them all, M4gery, DMR, MSR, doesn't matter I can keep them all, just all have to be chambered for the same cartridge.A question posed by my brother.

obviously the first thought that came to me was the 223 Remington / 5.56 NATO. It’s the iconic AR-15 cartridge. From ground hogs to deer, there is a loading that would work. But no, I passed on that.

The 300 BLK / 300 Whisper? I have a long history with this one. I like it…a lot. But it’s velocity challenged. I know it can reach out there to 200 yards, but in reality, it’s a 100 yard cartridge for me. Another pass.

The 277 Wolverine? I think it’s what the 300 BLK wants to be. Varmints to deer to hogs. This cartridge shines. But nope, I passed.

The 25/45 Sharps? Another good one. It could be better though. Had they just shortened the case a smidgen so it could take advantage of the heaviest .257 bullets. I passed.

The 300 Ham’R. I think this could possibly be the ultimate AR-15 cartridge. I still want to build one. Maybe I will get around to it. But since I have no personal experience I passed, reluctantly, but passed.

I rejected any cartridge that did not have a standard STANAG case head. Remember, I had very bad experiences with the M16A1 during my active time in the Marine Corps and worked in the armory as a reservist. I just do not like to stray from the norm.

So what cartridge did I choose? The cartridge that I so much want to hate, the 350 Legend. It has the disadvantage that the case can not be made from the 223 Remington like all the others, but I really don’t see much more negative. True, it’s certainly not the best for ground hogs, but it can be loaded with the lighter bullets intended for 380 acp and 9mm Luger and it can at least play the game. Step up to coyote sized varmints and it starts coming into its own. It has proven to me to be much more effective on deer and pigs than the other cartridges mentioned that I have used. and it is effective out to 200 yards, maybe a bit more. If I wanted to use it for home defense, I could certainly build one in pistol configuration. And finally as a range toy, it can be fired as cheap as the 223 Remington even if you do not reload.

So there you have it, my choice for the perfect AR-15 cartridge. At least for today, my mind is subject to change. I am fickle like that…(thinking 6mm ARC, that cartridge intrigues me)

 

[KSR]

Due to commonality and availability if for some reason I could only have one AR chambering it would be the plain ole vanilla .223/5.56.

 

[Pistolkitty]

.223/5.56 here.

My main purpose for ar-15 is self/home defense against bad people. I have other rifles for hunting purposes and yet others for critter defense large and small.
.223 and 5.56 current stock is sufficient, and finding more is easier and more cost efficient than finding just about any other caliber, save for 9mm.

 

[ajole]

You bypassed the 6.5 G and AR-47’s. I know they use a different bolt…but they could fill the niche.

My solution may turn out to be AR15 size/weight, but in .308. I get the SFAR on Monday, I know it has proprietary bits, but…I’m curious how it stacks up. Obviously not within your parameters.😉

If forced to stay in the STANAG world, I’d do 5.56. Ammo availability in terms of quantity and variety, the plug and play nature of bits and parts, and my own situation….I have more than a few already, from 4-20 inch barrels, pistols, fast and light carbines, middle ground rifles, and more dedicated longer range rifles.

 

[Dagwood]

I am inclined for availability purposes to agree with 223/5.56, but 6.5 Grendel has been one of my favorites for awhile. I would consider 7.62x39 as well, but I am already invested in Grendel and the ballistics are better.

 

[Delbert]

I think the 7.62x39 gives just as much reason to have in a caliber as 223/5.56 here in America, at least. While being a larger 30 caliber compared to 22 caliber size, the price cost for ammo is about the same, while also giving good ballistics and availability is worldwide due to also foreign military usage, so this is a cartridge that won't be shelved anytime soon and the AR15 built for this caliber eats it up like your fat date at an all-you-can-eat BBQ rib joint.

Those that also have or collect military/sporterized rifles like Mauser, Springfield, Enfield, Remington in 30-06 have very capable "only one" type guns too. In new(er) models, like Mossberg, Savage, Marlin and others, it's hard to find another cartridge with such worldwide capabilities in an off-the-shelf ammo. Of course the costs have risen sufficiently since Covid and the supply/manufacture shutdown for components.

 

[adam01364]

.223 / 5.56 for me. Main purpose is self defense/ protect property.

 

[greg_r]

I think the 7.62x39 gives just as much reason to have in a caliber as 223/5.56 here in America, at least. While being a larger 30 caliber compared to 22 caliber size, the price cost for ammo is about the same, while also giving good ballistics and availability is worldwide due to also foreign military usage, so this is a cartridge that won't be shelved anytime soon and the AR15 built for this caliber eats it up like your fat date at an all-you-can-eat BBQ rib joint.

Those that also have or collect military/sporterized rifles like Mauser, Springfield, Enfield, Remington in 30-06 have very capable "only one" type guns too. In new(er) models, like Mossberg, Savage, Marlin and others, it's hard to find another cartridge with such worldwide capabilities in an off-the-shelf ammo. Of course the costs have risen sufficiently since Covid and the supply/manufacture shutdown for components.

Remember, this is the AR-15 platform. I don’t dis-like the 7.62x39 cartridge, I have several rifles for it, the Mini-30, SKS , AK, and the Howa mini action. I just do not think that cartridge belongs in the AR platform. Remember, the bolt is a wear item, the further you get from standard the more it wears. That is the main reason that I have not built a 6mm arc, and one of the reasons that I got rid of my 6.5 Grendel. The other is that it’s velocity challenged.

 

[greg_r]

You bypassed the 6.5 G and AR-47’s. I know they use a different bolt…but they could fill the niche.

My solution may turn out to be AR15 size/weight, but in .308. I get the SFAR on Monday, I know it has proprietary bits, but…I’m curious how it stacks up. Obviously not within your parameters.😉

If forced to stay in the STANAG world, I’d do 5.56. Ammo availability in terms of quantity and variety, the plug and play nature of bits and parts, and my own situation….I have more than a few already, from 4-20 inch barrels, pistols, fast and light carbines, middle ground rifles, and more dedicated longer range rifles.

rejected any cartridge that did not have a standard STANAG case head

Did not skip the 6.5 Grendel. I rejected it out right.

I do like the 223 / 5.56. I have rifles in 223 REM, 223 Wylde, and 5.56. I person could do a lot worse.

I predict you will like the SFAR.

 

[Delbert]

Remember, this is the AR-15 platform. I don’t dis-like the 7.62x39 cartridge, I have several rifles for it, the Mini-30, SKS , AK, and the Howa mini action. I just do not think that cartridge belongs in the AR platform. Remember, the bolt is a wear item, the further you get from standard the more it wears. That is the main reason that I have not built a 6mm arc, and one of the reasons that I got rid of my 6.5 Grendel. The other is that it’s velocity challenged.

Oh I do have a few AR's that I've built and not built. I have them in 223/5.56 (in unlined and chrome-lined barrels), and 223 Wylde.

I suppose one thing the 223/5.56 chassis does good is also having the ability of just a magazine/BCG change and it can go from centerfire to a rimfire while still retaining the stock upper and lower assemblies. I don't know of any other firearm that can do this reliably. I really should get a rimfire conversion kit now that I think about it.

 

[greg_r]

Oh I do have a few AR's that I've built and not built. I have them in 223/5.56 (in unlined and chrome-lined barrels), and 223 Wylde.

I suppose one thing the 223/5.56 chassis does good is also having the ability of just a magazine/BCG change and it can go from centerfire to a rimfire while still retaining the stock upper and lower assemblies. I don't know of any other firearm that can do this reliably. I really should get a rimfire conversion kit now that I think about it.

1911

 

[backbencher]

Remember, this is the AR-15 platform. I don’t dis-like the 7.62x39 cartridge, I have several rifles for it, the Mini-30, SKS , AK, and the Howa mini action. I just do not think that cartridge belongs in the AR platform. Remember, the bolt is a wear item, the further you get from standard the more it wears. That is the main reason that I have not built a 6mm arc, and one of the reasons that I got rid of my 6.5 Grendel. The other is that it’s velocity challenged.

I think all cartridges that fit belong in the AR-15 platform, and for those that don't fit, there's the POF/Ruger Rogue/SFAR until we can get some more side-feeding uppers.

Isn't the 6.5mm Grendel supersonic to 800m in the right loading?

 

[Think1st]

Accounting for the fact that a 7.62x39 bolt is a wear item and that I'd have to keep a spare around, I would still go for the 7.62x39 round as my single cartridge. A 122-124gr round will hit a torso plate at 500yds, but a 154gr soft point, while having less effective range, will still pole axe deer and could fell elk at closer distances, too. It's a versatile round and quite prolific, so the cost isn't prohibitive.

 

[backbencher]

Accounting for the fact that a 7.62x39 bolt is a wear item and that I'd have to keep a spare around, I would still go for the 7.62x39 round as my single cartridge. A 122-124gr round will hit a torso plate at 500yds, but a 154gr soft point, while having less effective range, will still pole axe deer and could fell elk at closer distances, too. It's a versatile round and quite prolific, so the cost isn't prohibitive.

And while it will crack bolt lugs, it won't be hammered home in a 5.56x45mm chamber by an H2 buffer or forward assist and blow up a gun like .300 Blackout will.

 

[Think1st]

And while it will crack bolt lugs, it won't be hammered home in a 5.56x45mm chamber by an H2 buffer or forward assist and blow up a gun like .300 Blackout will.

Absolutely. There are just too many stories of that happening. The ammo is also a LOT more available off the shelf, and you can stack sealed spam cans of the stuff pretty cheaply.

 

[lklawson]

I don't really have anything meaningful to add to what's been said. However, I always find myself draw to odd and unusual cartridges. I own .38 S&W, 7.62x25, 9mm Largo, 9mm Makarov, and the latest 5.7x28.

So, given that I'm not right in the head, I'm thinking for an AR chambering... 38-40. 'Cuz why not have an old-school oddball 10mm?

To be a bit more serious, I'd have to waffle between 5.56/.223 because of it's general flexibility and ubiquity, or maybe either the 6.5 Grendel for more efficiency and downrange energy or the 300 BLK for heavier bullets, great flexibility, and similar ballistics which could range from subsonic/suppressed and .357 Mag on one end to encroaching on on the classic 30/30 on the other.

Most of the mainstream cartridges available to load in the AR15 platform have a lot of flexibility and I guess most of them could work just fine for a wide range of applications.

So, yeah, 38-40.

Peace favor your sword,
Kirk

 

[backbencher]

I don't really have anything meaningful to add to what's been said. However, I always find myself draw to odd and unusual cartridges. I own .38 S&W, 7.62x25, 9mm Largo, 9mm Makarov, and the latest 5.7x28.

So, given that I'm not right in the head, I'm thinking for an AR chambering... 38-40. 'Cuz why not have an old-school oddball 10mm?

To be a bit more serious, I'd have to waffle between 5.56/.223 because of it's general flexibility and ubiquity, or maybe either the 6.5 Grendel for more efficiency and downrange energy or the 300 BLK for heavier bullets, great flexibility, and similar ballistics which could range from subsonic/suppressed and .357 Mag on one end to encroaching on on the classic 30/30 on the other.

Most of the mainstream cartridges available to load in the AR15 platform have a lot of flexibility and I guess most of them could work just fine for a wide range of applications.

So, yeah, 38-40.

Peace favor your sword,
Kirk

Gonna use a Desert Eagle magazine?

 

[lklawson]

Gonna use a Desert Eagle magazine?

The 38-40 is both a rimmed and a tapered cartridge. Basically a 44 Mag necked down to .40 / 10mm so the 44 Mag DE magazine might work.

Peace favor your sword,
Kirk