.300 WM: Will Berger 230 gr Hybrids stabilize in a 11 twist barrel?

[BravoSierra]

Been looking all over for 208s amax, 215 hybrids, 225 bthp for my win mag (to no avail) when I ran across some 230 hybrids. Before I pick these up, I'm wondering to what degree they will stabilize. My stick sports a Broughton 5c 28" tube, 11 twist. Wanted a load that would feed from my AICS mags, about 3.6 coal. Anyone try these in their 11 twist, thoughts, or recommendations?

 

[Aimsmall55]

Been looking all over for 208s amax, 215 hybrids, 225 bthp for my win mag (to no avail) when I ran across some 230 hybrids. Before I pick these up, I'm wondering to what degree they will stabilize. My stick sports a Broughton 5c 28" tube, 11 twist. Wanted a load that would feed from my AICS mags, about 3.6 coal. Anyone try these in their 11 twist, thoughts, or recommendations?

Litz is pretty adamant about the 1:10 but who knows.... I shoot the 208's out of a 1:11.25 .308 and they shoot lights out. All you can do is try....

 

[BravoSierra]

Thank you, I know that the hornady 225s are fine, but 230s may be a bit too much. I'll just get the 230, i can always trade out if it doesn't work.

 

[Disturbed]

You could try it but don't invest in too many before testing them.

 

[BravoSierra]

Thanks, i figured as much. Just playing with the JBM stability calculator this morning. For the sake of posterity im posting this. Im using a constant velocity of 2800 fps for comparison:

Berger 230 Hybrid
Length: 1.640"
Factor: 1.185
G1 BC: .743

Hornady 225 BTHP
Length: 1.585"
Factor: 1.281
G1 BC: .670

220 SMK
Length: 1.493"
Factor: 1.491
G1 BC: .629

Berger 215 Hybrid
Length: 1.620"
Factor: 1.148
G1 BC: .696

Hornady 208 AMAX
Length: 1.533"
Factor: 1.305
G1 BC: .648

I know the 225's are stable out to a mile from my search, i think ChadTRG runs that in 11 twist. But the 230's are really pushing the edge of stability. I think i'll just wait in backorder hell for the 225/208's to be safe.

 

[BryanLitz]

What altitude are you primarily shooting?

You want the stability factor (SG) around 1.4+. Your 1:11" produces an SG ~1.2 around sea level which should work, but is a little low (technically anything above 1.0 'should' work, but you want a margin for error). At 5,000 feet altitude, your 1:11" produces an SG ~1.4 so it would be totally fine there.

Temperature plays a role as well, with warmer air being good for stability.

In cases of questionable stability, it's also a good idea to verify your actual barrel twist rate.

Take care,
-Bryan

 

[varmint slayer]

[MENTION=18711]BryanLitz[/MENTION] what kind if velocity have you seen with these in a 300WM? Seems like if you could get 2800 FPS, the ballistics are a hair better than a .338 Lapua in some cases.

 

[BravoSierra]

Primarily 500-1000 ft asl, north texas plains. I just used standard temp of 59 and pressure 29.92 that jbm defaults to. Primarily, id be shooting it from about 45 to 95 degrees OAT. I know it would be on the edge, but id want a bit of margin to be safe.

 

[BravoSierra]

Thanks Brian. Playing with JBM at 45 OAT, the factor is 1.153 at 29.92 hg, and the factor gets better as pressure drops. Conversely, gets worse as it increases. Makes sense, as density altitude is changing. Whats interesting is when its 95 OAT, and low pressure of 28.9 hg, the factor creeps up to 1.31.

Sounds like if i could actually get good velocity, and its hot and low pressure outside, id have just the ticket. And texas isnt exactly cool for most of the shooting months.

Well, wont hurt to try!