- February 24, 2019 at 11:27 pm #69205
i have been thinking of a new upper for my ar. I would think a 300 bo would be about perfect for a 200 yard cast bullet shooter. The problem is there all to fast of a twist for cast. What if I got a barrel chambered in 300 bo with a 1/14 or 1/12 twist? I will only want to shoot 100 gr to maybe 168 gr cast lead bullets or jacked .No heavy subsonic bullets . Most of my shooting will be with cast at 100 yards but would like to try 200 with either. Not really wanting it for hunting deer . What do you all think of this round as a cast bullet shooter
- February 28, 2019 at 10:26 am #69206popperParticipant
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My 18″ 1:10 carbine works fine for cast, 145gr PB. I push it (2-2.1K fps) and get good results. Works good with vmax & ssts, 150gr SPP and 168 Amax (just OK) @ 100 but case vol. is low so the moderate heavies can’t be pushed too fast. 1:8 might help there. You will have to push the light ones pretty hard to get the gas to work so maybe the 1:12 would work better. I run the 100gr half jacket in 1:8 pistol with pistol powder and they go fast but won’t cycle. IMHO, 14 is too slow, 12 might work, 10 works fine.
- March 2, 2019 at 7:35 am #69207Larry GibsonParticipant
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I think a 14″ twist would fit your needs very well. The throat is starting to erode in my 31″ 30×60 XCB (DAWN with a Broughton Palma contour barrel) which has over 3,000 top end loads pushing 49 – 50,000 psi. When the throat is gone I’m having Tim put the front 24″ of barrel on my Mini MK X in 7.62×39 and chamber it in same. I think the 16: twist will be just perfect for 118 to 125 gr cast at max velocity. Might even be very good with the 165 gr 30 XCB bullet.
- March 2, 2019 at 10:08 pm #69208
Thanks for the info. Right now I got a extra lower needing to be built. I was thanking getting a 300 bo in 1 /12 or. 1 /14 twist. For mostely cast or a 9 mm 9×19 rifle leingth upper to use for my lower using a mean mag converter. There is also other converters I can use. I want to use mostely lead bullets for target pratice . Each caliber would be cheep to load if we ever have a powder and primer shortage again. I mostely only shoot 100 yards or less now but can shoot up to 300 at my range. The problem is finding a bo barrel in 1 -12 or 1 /14 . I found a few but are kind of high custom barrels. I have found one company that’s decent in price will have to find out thanks
- March 3, 2019 at 10:37 am #69209kensParticipant
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300BO should work very well on a slow twist. After all, the .30BR is a small capacity case well proven in slow twist with light jacketed in bench rest competition.
300BO or 7.62×39 are both small capacity cases and that lends itself to a efficient cartridge. I had a Mauser98 with a generic 7.62×39 barrel (.308″) and it impressed me with comm-bloc ammo. I experimented briefly with cast and showed promise but I soon hit Larry’s RPM limit with cast. It acted like it wanted to do well though. It is easy to go up to .30-30 power with Lee 170gr cast. Larry’s mini mauser would be a hoot. Small, lightweight, and every bit a .30-30 hunter.
Of course the .30XCB would likely be a natural for this.
Not mention a little light plinker might go to 2900fps on prairie varmints.
My M98 7.62×39 had a x39 chamber and .308 bore, the large throat didnt seem to bother it. I did manage a few 1moa groups but did not push farther for custom ammo. If you seek sub moa shooting you may want a .30 throat, but the x39 throat will get equal to 1 moa, I cannot verify smaller than 1 moa.
- March 3, 2019 at 11:00 am #69210
Only problem I see is getting a ar barrel with a slow twist in 300 BO. Who makes them or are they a custom made only option. I have emailed the ar guy yesterday so still waiting. Apache gun works also does custom barrels but I don’t see ar barreled on his web site. Thanks for any info on where to buy a barrel
- March 3, 2019 at 12:55 pm #69212popperParticipant
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McGowan or X-caliber HBAR carbine 1:11,12 280$ normal or 5 grove.
Took a while to get mine from McGowan (220$ IIRC and they put it together for me), several years ago but a good barrel. I chose 10 as I use 10o – 190gr so it’s general purpose – and the slowest I could find at the time.
Let’s add a twist. Larry uses 144k for the rpm threshold. IIRC he uses mostly #2 alloy. If you want softer alloy, you may want to go to the slower twist. Bama found he didn’t smoke the fast stuff if he added copper to the alloy. I used low Sb in my 1:8 pistol, pushed pretty hard and it worked, just Cu/Zn/Sb. All my moulds are essentially smooth sided so lots of bearing surface. So it’s not just stability for bullet length but fps & alloy too.
- March 3, 2019 at 3:15 pm #69214
I also found xcaliber barrels also in 1-12
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