Can you all help me build my AR

[43PU]

I’m in bit of a dilemma I have five ARs in different calibers 204 Ruger, 7.62x39,450 bushmaster,two in 556. I have a bolt action Ruger in 7.62x39,6.5grendel and 300 blackout. I have tried the AR blackout but could not get it to run with lead cast bullets so it went away and replaced it with a Ruger 300blk . I am wanting to build a ultralight hunting/planking A.R. 15 I am thinking of a 6X45 or a 556 in a 1/12 twist I’m wanting something that is a parent case of 223/556 and would be able to shoot a decent weight bullet to around 23-2400FPS. what would you all do and why

Thanks 43PU

[lefty o]

if i were to do another, it would probably be 277wolverine.

[jmort]

Try the .300 ACC BO again. The parent case is .223, but it is so popular that you can just buy ready to go cases. You can get a PSA .300 BO for $450 and it will go bang all day and night. Just got a 8.5" AR pistol and it is worth every penny.
Go light, or go heavy sub-sonic with a can.
With the BATF giving the OK to the SB Tactical SOB Pistol brace, it is perfect all around.
https://palmettostatearmory.com/psa-8-5-pistol-length-300aac-blackout-1-8-nitride-7-lightweight-m-lok-moe-sob-pistol-5165449855.html

[jmort]

BTW, all AR15s will be more of a challange with cast. Caliber is not the issue.

[Omega]

+1 on the 277WLV, there is commercial brass available now and close to becoming SAAMI, and a proven hunting round.

[Combat Diver]

I would suggest for a lightweight rifle using a A1 upper, pencil thin 16" bbl, CAR handguards and Colt N1 buttstock. For the gas issue with the .300 next time try a adjustable gas block. I wouldn't mind building either a 6x45,.25-45 Sharps or 6.8 SPC II. 5.56mm with a .22LR conversion best for a plinker however.

CD

[jmort]

I would not be surprised to see the .277 Wolverine take off or disappear. It makes a lot of sense. I hope it makes it. Right now it is a Wildcat. We shall see in the fullness of time.

[Elkins45]

I have had challenges with one particular 300 BO barrel in terms of accuracy, but I have three uppers ranging from 9.5 to 16” and all have been quite reliable with cast. What sort of problems were you having?

[43PU]

I have had challenges with one particular 300 BO barrel in terms of accuracy, but I have three uppers ranging from 9.5 to 16” and all have been quite reliable with cast. What sort of problems were you having?

I had a 16” 1/9 twist 300 upper, the throat was so tight that any cast bullets over .299 nose would not chamber. It would shave a lead ring off the bullet every time it cycled it even had a problem with M80 FMJs

[popper]

decent weight bullet to around 23-2400FPS That is a hot 110gr load in BO. Lightest cast I run is 145gr @ 2100 tops in the carbine. 10" pistol with light barrel will get you under 5# and is accurate. Yea, you had a barrel problem. I run 110vmax to 185gr RD cast in mine.

[Handloader109]

My 300BO can be a challenge if I PC too heavy, but if you go with a coat that is not too heavy, it works. CFE Blackout powder cycles all I have tried in 9" barrel with my suppressor.

[dogmower]

i shoot the lyman 311413 (about 170 grains), pc, over 18-20 grains imr 4198 in 300 b.o. shoots grapefruit sized groups at 300 meters, cycles the action perfectly, and doesn't lead.
also the rcbs 130 grain gc mold (forget the #) in 7.62x39 over 25 grains rl 7. shoots great in my ar, ruger bolt gun, ak and sks.

[StratsMan]

CFE Blackout powder cycles all I have tried in 9" barrel with my suppressor.

+1 /\

It may be interesting to add another caliber, but it may be more satisfying to figure out the BlackOut rather than letting it best you...

I had to abandon my first 300 BO pistol barrel (7.5") and replaced it with a 9" ... Much easier to get reliable function with Lee 230gr cast boolits now. The bore ride is a little small, so the throat doesn't jam up like some of my other molds... And it cycles reliably with or without the can at sub-sonic speeds using CFE BLK or 1680....

[roysha]

Since you specifically stated a preference for something using the 223 case as a base, I"ll throw in my $.02 worth.

My Grandson and I built a 270-223 on an XP-100 with a 16" barrel. I don't have the exact numbers handy but it chronographs in the area of 2325 fps, with the Sierra 130 grain SPT flat base. I don't think you could quite reach that velocity because of having to seat the bullet somewhat deeper in the 223 case to function through the magazine. However, since the project started out as a 270-221, (sort of a 270 Whisper) and chronographed just shy of 2000 fps with the same bullet, you should be able to come close. Since the XP is a single shot we throated the barrel deep enough so we can seat the bullet only about 1/8" into the case. Very accurate and with the custom stocked XP, he's a left handed, very pleasant to shoot.

[mattw]

You know, I feel your pain with cast in a 300 BO. I have been chasing that goal for a few weeks and thought I was close. But this weekend, a minor change in the bullet profile jacked my pressure way up. I switched to RCBS 150gr FP and they cycled fine, but the load that I had worked up for the Lee 7.62x39 bullet was to hot??? I am about out of time for this year, gonna get cold and crappy and I am losing 2 weekends to deer season.

[Elkins45]

I had a 16” 1/9 twist 300 upper, the throat was so tight that any cast bullets over .299 nose would not chamber. It would shave a lead ring off the bullet every time it cycled it even had a problem with M80 FMJs

A throating reamer from Brownell’s is only around $30. I bought one for my problem barrel but haven’t gotten around to using it yet. That might solve the problem if you still have the barrel.

[DougGuy]

A throating reamer from Brownell’s is only around $30. I bought one for my problem barrel but haven’t gotten around to using it yet. That might solve the problem if you still have the barrel.

If that's a hardened barrel that reamer will be toast in the first 1/8 of a turn. Gone. Ruined. HIstory.

The $30 reamer is likely the worst choice, they make the pilot on those small enough to fit any barrel which effectively makes it a non piloted reamer if it doesn't ride snug in the lands, you might as well use a Harbor Freight drill bit.

[Tracy]

.300 Fireball. For practical purposes it is a .300 Blackout with a 1:12" twist. It's pretty much a custom barrel now, but it used to be available as a production barrel. Anyone who has shot cast in .30-30 can tell you that 170 grain boolits at 1200 fps and up are no problem in the 12 twist.
In fact I wouldn't mind trying one with the 1:20" twist that .30 Carbine barrels use. That should work fine with blunt cast boolits up to 150 grains, and probably jacketed spitzers up to 125-130 grains.

That doesn't meet everyone's needs, and it might not meet yours. But I think it would be great for my needs.

[Baltimoreed]

Looks like you’ve got a pretty wide range of AR rifle cartridges there 43PU. Have you thought about a pcc, pistol caliber carbine? assuming that you do shoot pistols. My first AR was a Seekins .300 blkout, the next 3 were dedicated greasegun mag .45acp’s. The .300 lower now has a dedicated cmmg .22 upper on it which I use alot more than the 300. I’ve shot my AR.45 carbines in ipsc matches and it’s a bunch of fun. Just a thought.