What Would be Your Next AR15 Caliber?

I looked for any recent threads on this discussion and didn't find any, so bear with me if this is a repeat of another thread.

I've got .223/5.56 covered and I'm thinking about what I want to do next. I've listed some options in the poll above, but that is certainly not an exhaustive list, just the ones that seem to be more common among the articles I've read and people I've talked to. The question is based on using a standard AR15 multi-cal lower.

One thing I know is that the 7.62x39 may not be a good option in a standard AR lower, but that's all I have on hand at the moment, so I'm leaving it on the list.

I'm leaning toward the 6.5 Grendel based on what I've read about it's performance out to long ranges over some of the other choices. I don't have any long range setups at the moment and it sounds like a good one to use for long-range fun, especially if you do your own hand loads. I'm not a hunter, so this would be strictly for learning more about long range shooting. I understand these cartridges can keep going well out to 1,000+ yards, which seems pretty impressive to me. I also understand it can be difficult to find ammo.

My second choice is a 9mm, just for cheap fun.

Third, I would love to do a 7.62x39, but from my research, it looks like it's best if you get a lower that will specifically work with standard AK mags, and it looks like those are limited choices at best at the moment. Maybe 5.45x39 would be a better choice.

.300 BLK sounds interesting, but I understand it's ideal for suppressed applications, and at this time, I'm not planning on running a suppressed setup.

So I'm curious, if you were looking at your next AR15 based build, what would you choose and why?

 

I kind of stated my reasons in the OP, but I was just more curious about other people's opinions for themselves rather than looking just for myself. I find it interesting why people choose particular calibers for particular reasons.

Since I don't hunt, knockdown power isn't a huge concern - but you never know, it could be something I take up some day.

For me, a 9mm would really just be a fun gun. I am a fan of pistol caliber carbines, but I don't have anything in an AR platform. 9mm is cheap to buy/reload and shoot, so likely it would be 100 yards or less. I read your thread on your 9mm build a while ago and it helped pique my interest in 9mm AR's

I haven't looked into the 25-45 Sharps, and since @Joe13 mentioned it too, I may need to take a closer look. It's a round I don't know much about.

Keep the opinions coming folks. I love hearing the why's and what's of the various choices. And again, I'm not necessarily looking for a specific recommendation for myself, just interested in what calibers get your interest.

 

I was reading about the .50 Beowolf recently. Yes, that does sound like a very interesting option.

 

I've seen his videos before, but I keep forgetting to go back to his channel. I'll be sure to check it out.

And apparently there is a new 25-45 Sharps round announced at SHOT show (posted on another thread) - apparently good for both hogs and bear. Even as a non-hunter that sounds like something I want to know more about:

 

I should mention too that I'm thinking of doing the 9mm as a pistol build. Again, all for fun, and I can always change it to a rifle later, so long as I don't create an SBR in the process.

 

Clearly, that is the only reasonable solution.

I'm going to need a bigger safe...