Is the .300 BLK the Ultimate.....

[Jsm180]

Exactly, I call it my garbage disposal. Got 556 brass with a boogered neck or shoulder? Make 300 blk brass out of it.

Pinch of powder and dab of lead. New primer and off to the races.

Lots of factors to consider in 'the ultimate' category but economy of brass (with right tools, made from free/cheap range brass) molds are plenty...mine eats almost every 30 Cal boolit I own. Capacity is same as 556, no special or proprietary parts, bolts or uppers- just a barrel swap.

Downrange energy for deer out to 150.

I think it's pretty awesome, some folks really balk at it....but especially today when ammo and firearms choice is in expensive or limited supply.... changing a barrel to change the game in medium game harvest is a no brainier.

300 blk makes some sense if you don't reload, but it makes all the sense if you do reload.

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Same here, I trashed a bunch of 223/556 by bumping the shoulder back too far. I had a spare lower, so I built a 300 AAC, perfectly logical in my book.

[Burnt Fingers]

There are no ars chambered in 30/30 or 308w though.

In AR platform (not AR10/SR25) there are alot of options from 25 sharps, 6.5 grend., 45 socom and 50 beowulf...but 300 blk is the easiest for cast, ease of conversion.

Like you I don't need the speed of 30/30, 308w or 3006 for my deer hunting (close in) 300 blk gives me the edge of smaller rifle, semi auto for follow ups on hogs, and more than enough penetration for all my deer hunting needs

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Ya do know the AR platform started out with the AR-10????

[Photog]

300BO is Meh in my book.
Loaded slow, its a Pistol caliber cartridge (9mm, 38spl/357mag, or 40s&w power)
Loaded sub-sonic- its a 45 acp
loaded fast pistol - its a 357mag carbine
loaded faster its a 30M1 carbine
even faster its a 30/30
even more- its 7.62x39
Then its done. It doesn't do anything different than what has been done before - except that it can be fired in an AR15.
My only 300BO is an 16" AR, and its fun and all, but I have other 30 cals that do the same things. For the time spent developing loads, it just adds to the confusion of what its supposed to do. Its better to get a 9mm upper for plinking/light duty, and a 7.62x39 upper for a hard hitting short range rifle, and of course a 556 upper for general use.
I think it comes down to your commitment level too. Do you want to develop a subsonic, semi auto heavy boolit load for the same upper that also shoots a 30/30 power load? (My Win 94 does that too) (And my 308 mauser does that too), (oh yeah, my 30-06 03A3 does that too) But then bolt guns can't chew through ammo like an AR can, so you get to reload more with your 300BO AR15. The only Semi rifle that I want to reload for anymore is the M1 carbine. Oh and the M1 Garands, but again I'm not just spewing lead at the range from those.
Tell you what is more fun - 38 special lever actions. Cheap to cast for, cheap to find brass for, easy to load, the brass never wears out, the brass isn't flung into the next county, low powder charge, my ears don't hurt after a session in the field, and I can hit what I want out to 100 yds for 5 cents per round. With 5gr of W231 under 125gr cast boolit my 38 spl is zipping along at 1400 fps, shoots 1.5 inches at 50yds, and is a hoot. Getting that fun out of 300BO from an AR takes much more work in case prep and loading, and then the 125gr boolit is too short and likes to jam in some mags or not feed smoothly.
YMMV, I don't shoot the 300BO much anymore.

[John McCorkle]

Ya do know the AR platform started out with the AR-10????

Don't think that's what op is talking about....and yes, fully aware ar 10 was first in line

Unless I am really missing the original question, op is asking about best caliber for cast in ar 15 platform

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[44Blam]

So, I have a cartridge that costs about 8 cents to load (assuming prices I bought components at and picking up range 223/556) for 300 bo and it is just super sonic. It cycles and shoots great. You need specific brass or turn the neck - either way. Sad part is you are limited by RPM to maybe 1500 or 1800 fps.
I think the 350 legend is a really great cast round as they tend to twist barrels in the 1:15 or 1:16 range. This means you can drive a boolit much faster. I've got a load that drives a 125 grain boolit (GC 9mm boolit) about 2500 fps. With great accuracy and no issues. The load I tend to go to is a 180 grain boolit at about 2000 fps and it is very accurate.

[Lloyd Smale]

300BO is Meh in my book.
Loaded slow, its a Pistol caliber cartridge (9mm, 38spl/357mag, or 40s&w power)
Loaded sub-sonic- its a 45 acp
loaded fast pistol - its a 357mag carbine
loaded faster its a 30M1 carbine
even faster its a 30/30
even more- its 7.62x39
Then its done. It doesn't do anything different than what has been done before - except that it can be fired in an AR15.
My only 300BO is an 16" AR, and its fun and all, but I have other 30 cals that do the same things. For the time spent developing loads, it just adds to the confusion of what its supposed to do. Its better to get a 9mm upper for plinking/light duty, and a 7.62x39 upper for a hard hitting short range rifle, and of course a 556 upper for general use.
I think it comes down to your commitment level too. Do you want to develop a subsonic, semi auto heavy boolit load for the same upper that also shoots a 30/30 power load? (My Win 94 does that too) (And my 308 mauser does that too), (oh yeah, my 30-06 03A3 does that too) But then bolt guns can't chew through ammo like an AR can, so you get to reload more with your 300BO AR15. The only Semi rifle that I want to reload for anymore is the M1 carbine. Oh and the M1 Garands, but again I'm not just spewing lead at the range from those.
Tell you what is more fun - 38 special lever actions. Cheap to cast for, cheap to find brass for, easy to load, the brass never wears out, the brass isn't flung into the next county, low powder charge, my ears don't hurt after a session in the field, and I can hit what I want out to 100 yds for 5 cents per round. With 5gr of W231 under 125gr cast boolit my 38 spl is zipping along at 1400 fps, shoots 1.5 inches at 50yds, and is a hoot. Getting that fun out of 300BO from an AR takes much more work in case prep and loading, and then the 125gr boolit is too short and likes to jam in some mags or not feed smoothly.
YMMV, I don't shoot the 300BO much anymore.

i do the same with my 9mm ar15s. The 16 inch gun shoots a 145 cast with 4 grains of surplus pr200 into 1 1/8 at a 100 yards. YUP a 100. My 4.5 ar pistol in 9 does 2 inch at 50. Good enough for the girls i run with. Brass is even cheaper then 38s these days and lasts a long time. 9mm ars have about replaced my 22lr shooting. Almost as cheap and the place i score mine at is WELL STOCKED Add to that a guy can put together a 9mm ar a heck of alot cheaper then your going to buy a marlin 94 or winchester for. Another plus is they use ar parts which i have drawers full of about anything that could possibly break and if it came down to it i could strip parts off of one to keep another going.

[milsurpcollector1970]

I have had nothing but problems getting the 300blk to chamber in the ar with cast also had issues with the 30 hrt (a rimless 30 herrett made from 6.8 spc cases)

I finally gave up on 30 cal cast in the AR

I even got a throat Reamer to try fix the issue

[Burnt Fingers]

I have had nothing but problems getting the 300blk to chamber in the ar with cast also had issues with the 30 hrt (a rimless 30 herrett made from 6.8 spc cases)

I finally gave up on 30 cal cast in the AR

I even got a throat Reamer to try fix the issue

Maybe it was you? I've had no problems as long as the OAL is correct. You were using a 300 BLK barrel right?

[Lloyd Smale]

I have had nothing but problems getting the 300blk to chamber in the ar with cast also had issues with the 30 hrt (a rimless 30 herrett made from 6.8 spc cases)

I finally gave up on 30 cal cast in the AR

I even got a throat Reamer to try fix the issue

sizing to 308 solved most of my problems with the thick brass made from 556. Never had a problem with factory 300bo brass at 309. But the 308s shoot just as well so thats the way i do it today.

[roharmon]

You got the bolt to go forward with a 300 BO in a 223?

If I wanted a cast bullet AR, I would want the .358 based on the .223 case, not the .350 Legend.

The .300 BO has one issue....it can be chambered in a .223 gun and the result is unpleasant. One mistake is all it takes.

[M-Tecs]

You got the bolt to go forward with a 300 BO in a 223?

http://bulletin.accurateshooter.com/...23-rem-barrel/

[roharmon]

Obviously I am not h]going to try it, but still seems unusual to me

[jim147]

It makes long skinny boolits that way.

[iomskp]

I had a 300bk in a bolt gun, the heaviest mold I could get locally was a 220 gr, it shot really well. I have since sold the rifle and am concentrating on my 7.62 x 39.

[Burnt Fingers]

You got the bolt to go forward with a 300 BO in a 223?

It's happened to quite a few people. It starts with having light boolits loaded in the 300 Blackout and involves at least one idiot.