My quandry friends. Contemplating 5.56 AR vs .300 Blackout. Wish to cast.

I suppose I really don't have a specific question folks. Mostly hoping for other's thoughts to ponder right now. Thanks to folks here and lots of time reading threads, tutorials and researching, I've become a so-so caster and real enthusiast about the art. I recently assembled an AR pistol in 5.56 from a Palmetto State Armory kit and am quite happy with the results. Accurate and just plain fun, I have another lower receiver waiting for surplus cash to appear (grin) to fund another kit. I had decided the next would be .300 Blackout because of the ease of casting for the round and powder coating the slugs for use in the gas operated gun. I'm a range shooter. I cannot hunt any more. I'm not a competitor either, shooting hundreds of rounds weekly. I also am on a fixed income and jacketed slugs are pricey.
Conversely, I've aged though and wish to limit calibers somewhat.
Am I missing an opportunity to enjoy casting for the 5.56 cartridge, experimenting with loads, and learning powder coating and gas checking? The .30 caliber round has more options of course. But is the 5.56 a good candidate too but I'm missing the signs? DO folks think maybe I'm setting myself up for frustration and likely failure wondering if I should just choose another 5.56 kit and learn to cast for this cartridge?
Thank you all for taking a moment to offer thoughts. Don.

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Who says you can’t do both? 223 is tedious, time consuming, full of rejection, but oh so satisfying with it all comes together. I guess you have to look at why you Cast to decide. If you Cast just to fill your ammo bug, then maybe not. But if you Cast for the journey of exploration just to see if you can, then by all means tackle the 223!

Wife and I shoot cast almost exclusively out of our .223 ARs. I cast em from range scrap, so it's free and that little pill doesn't go through the lead supply very fast either.

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If you enjoy shooting, BO. If you enjoy a challenge, 223. The benefit of 223, flat shooting, HV, become difficult with cast. I, like you am not much of a hunter nor competitor, I've never shot a 223 as it doesn't have a purpose for me. BO is cheaper to shoot, mould and sizer costs will be the same.

Both!
.223:
https://videos.utahgunexchange.com/w...MgEJVyjo9.html

Blackout:
https://videos.utahgunexchange.com/w...RKgQBEUFe.html

I shoot the Grendel and my next AR is going to be 277 Wolverine.

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Thanks a goodly amount folks.
I also wonder if I do choose to begin casting for the 5.56, would it be better to choose a mold for the heavier slug weights as a starter point? The Blackout cartridge is well suited to subsonic (according to my reading), however the 5.56 was born to be wild. My 5.56 barrel is 10.5 inches long, and its twist is 1 in 7 inches. As a side note, slow is fine with me, as my favorite loads in .38 and .357 have always been 125's at under 900 FPS with Trailboss. But the 5.56 may require faster for semi-auto function. Hmm. Don.

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Originally Posted by Tallbald

Thanks a goodly amount folks.
I also wonder if I do choose to begin casting for the 5.56, would it be better to choose a mold for the heavier slug weights as a starter point? The Blackout cartridge is well suited to subsonic (according to my reading), however the 5.56 was born to be wild. My 5.56 barrel is 10.5 inches long, and its twist is 1 in 7 inches. As a side note, slow is fine with me, as my favorite loads in .38 and .357 have always been 125's at under 900 FPS with Trailboss. But the 5.56 may require faster for semi-auto function. Hmm. Don.

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Mine are 1:7 twist. Carbine length gas system. I shoot 55gn pc'd, no gas check, over 20gn imr4895.

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Thank you friends. This is great information to have and digest. The holiday sales at PSA are around the bend, and I'll surely have a better idea about what's the way to go by then. Don.

You already have a 223, just cast for it and save the $ for whatever.

I vote for one of each 5.56 & 300AAC. I shoot FMJs out of 5.56 and cast out of my 300AAC. I think both calibers work better that way. Little 55gr .223 works better with FMJs at those speeds but for 50 or 100 yard plinking I prefer 300 blackout. Bigger hole, harder steel hit and cheaper then store bought 9mm. My cast 155gr over nice charge of H110 only costs me about $0.07 per round.

If you are a “so so caster”, you may find it rather frustrating to deal with the .223. But then again, it depends on your expectations. 5 MOA @ 2000 fps will be a lot easier than 2MOA @ 2800 fps.

It will not require a large investment to start casting for the .223.

One other consideration, if you do not plan to shoot a lot, building a dedicated AR in a larger caliber for cast bullets may not be worth it. Monmouth, a vendor here, has good sales on .224 SP Hornady bullets.....I got 6000 for $420. Like you, I looked at the .300 BO for the same reason and decided against it. Making the cases, buying a good mold and sizing die ($100+), casting, sorting, weighing, and adding gas checks looked like more effort than I wanted to spend.

I bought a 80gr NOE 223 mold. Already had a 55gr. Mostly it was for subsonic, with a fixed velocity, weight is what you want. They shoot great sub and full power. Mold can cast PB or GC, PB works fine subsonic. 55gr works well in my 22 hornet.

Plenty of other calibers you can build an AR in. I looked at 300BO, but always find something else. Another 80% lower was in the mail today for another lower. Fixed ACE stock on the one lower is not easy to remove. I wanted an M4 stock to be able to compare back and forth. Will imagine the 223, 9mm, 450bushmaster will grow soon enough to include another caliber.

At 53, I just bought my first AR. It is a 1:8 300 black out 16" barrel with a pistol length gas system. I would have liked a carbine length gas system, but at $400 for a complete PSA lower and a Radical upper unfired with an Alpha bolt... I could not pass it up. It had a Radical m-lok hand guard that did not have rails everywhere, so it sits well in a rest and felt great off hand. I have not had much time to shoot it, but I had a few Lee 155 grain PC'ed slugs and had to try them out! They worked great, I will be doing much more of this. I do not know how well cast will work in the current 1:7 5.56 barrels, I am thinking about an upper in 223 Wylde with a 1:10 barrel... I think it will provide great cast results. I would like to shoot without the PC as I am not very good at that process, but I am not sure that is a good idea.

A very experienced OP on another board is trying for 2900 fps heavy (223) boolit PCd, in MVP rifle - 2" @ 100 is best he can do so far. Add an AGB to the pistol port and it will work fine. BO uses 30% less powder and anything from 100-250gr lead. So there is some cost tradeoff but terminal performance can be anything you want, effective hunting range is typically 200. Think cheap to shoot 30/30 or x39. PC works great in the BO, keep trying, you will get it right. I've pretty much given up on HiTek for rifle as it's just too much trouble. Works well for large batches of pistol but if you mess up, no way to fix. I'm not looking for MOA @ 100 from 40SW or 9mm.

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Originally Posted by Markopolo

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Who says you can’t do both? 223 is tedious, time consuming, full of rejection, but oh so satisfying with it all comes together. I guess you have to look at why you Cast to decide. If you Cast just to fill your ammo bug, then maybe not. But if you Cast for the journey of exploration just to see if you can, then by all means tackle the 223!

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Think this is a great perspective.

I am a huge fan of 300 bo...there are alot of reasons but I get to be involved in making the brass...casting...hunting plinking target home defense...I use 300 blk for everything...but that is me. Not only may your mileage vary we are totally different people and the nuances of casting.223 may far outweigh anything else.

It takes alot of finess to cast 223 from what I read here...tried it some...can get it to go bang bang but nothing close to what I can do with 300 ...but to be able to do it well and get good results must be absolutely thrilling!!

I get my kicks experimenting with paper patching...it fits that intricate and detailed process for me in the "technical achievement" category. I think 223 would easily do that for you too especially if you give yourself good goals to stretch for.

Good luck and keep us informed!

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In my experience, the larger the boolit, the easier it is to get better results with powder coating. With the 300BO, you may not even have to use gas checks. That will keep costs down. There are people who shoot .223 PC with out GCs too.

I want to get a .458 socom upper and run my 350 NOE ranch dog boolits through it... With a near max load - against some unruly watermelons and soda bottles.

With the powders that will function an AR15 bolt system you will most likely need to use gas check with the 300bk.

Making cases for the 300blk is super easy.

Once fired 300blk cases are also avialible for reasonable prices.

Imo the 300blk is basically a 357 in a ar15 platform.

I have not tried very hard yet am right at 2moa at 100 with mine. But I'm shooting a 14bhn lee 312-160gr sized to .310 powder coated and gas check bullet out of 10" pistol. Velocity is 1700fps and I use 15grs of little gun or h110. My goal for this load was a fun inexpensive plinking load with 500rnds per 1lb of powder.

In conclusion I would go with the blackout. Its easier to cast for, easier to work up a load with and flying crayons are just fun.

I've only been casting for 35+ years, so I don't have all the answers.
However, I can tell you, .22's are a challenge for some, and genuine PITA for most folks.
You'll have better success earlier with 300 BO.
If you already have .30 caliber molds, likely you'll have one that works reasonably well.
OLD Saeco 315, Lyman 31141, RCBS 165 SIL or similar RCBS 150, or RCBS 180 grain, have worked for me, with SEACO being the easiest.
The Ranch Dog 165 ogive is a bit too fat for my chamber without seating more deeply than I'd prefer.
I have a 247 grain designed for the 300 BO but I've not yet used it.
Keep us posted, and good luck.