bullet size vs. bore size vs. twist

[mortre]

I've never worked with cast bullets before, so some of this may seem like basic info but...

I'm thinking of building up an upper for my AR-15 to use with a straight walled .223 Rem case. This wildcat can produce 2000 fps with 200 grain bullets (according to the smith with the reamer) in a carbine barrel. What I am wondering is what bore size should I be looking for in the barrel? Should I just ream out a new chamber in a 9mm barrel, or try and order a .357 or .358 caliber barrel? What twist rate would I need to stabilize these bullet weights.

[Blammer]

I'd try for a standard 357 mag barrel with a 1:14 or 1:12 twist

[Blammer]

I'd also specify the size of the gas port in the barrel, or at the worst get an adjustable gas block.

[Blammer]

20" barrel with Rifle lenght gas tube for sure.

[Blammer]

or just forget it and get a 458 socom and shoot 45 cal cast boolits in it. MORE thump...

[mortre]

Actually I've talked to 2 AR-15 smiths and 1 said a carbine gas system MIGHT work, but a rifle length one wouldn't (pistol powders, too fast for the rifle length tube system). The other one said my best bet would probably be a blow back system like (other) pistol cartridge AR setups used. Starting loads are supposed to use mid-range .357 maximum data.

I want to try this so I don't have to worry with another type of brass. Just do some annealing and necking on spare .223 brass =p.

Oh yeah, I'm not trying to kill elk here. Feral hog's would be the biggest thing I'd be using it for.

[Larry Gibson]

I'd go with the carbine gas tube, adjustable gas block and 14" twist barrel. I'll venture that the cartridge will be optimal with 150-160 gr bullets (cast or jacketed) as anything heavier will eat up too much case capacity. I'd also venture powders in the 2400/4227/H110/296/4198/5744/4759/322 will give optimal performance, perhaps a tudge more than a .357 magnum in a 20" barrel or about the same as a .357 Maximum. Magazine length will limit your OAL and choice of bullets on the heavier side. Should be kick ass with 125 FP/XTPs on jack rabbits!

Larry Gibson

[mortre]

UP, Wa. Thats not too far from my neck of the woods! I'm down in Yelm.