Frank:

Sure it can work under certain weather conditions or at short distances and when you increase the velocities to increase the spin rate.
How does it perform at 300 yards?
Can you verify your barrel twist to decimal one place? Since you are on the edge we need to know your exact twist.

Caliber      0.321      Inches            
Bullet Weight      187      Grains            
Bullet Length      1.18      Inches            
Barrel Twist      15      Inches/turn            
muzzle velocity      1600      fps            
Temperature      100      degrees Fahrenheit (59 is standard)            
Pressure      28      inches of mercury (29.92 is standard)            
                       
Sg =      1.39                  


I prefer to select a bullet and appropriate barrel twist that will perform well over longer distances and under all weather conditions without pushing cast bullets at high velocities.

Caliber      0.321      Inches            
Bullet Weight      235.1      Grains            
Bullet Length      1.299      Inches            
Barrel Twist      11.5      Inches/turn            
muzzle velocity      1470      fps            
Temperature      50      degrees Fahrenheit (59 is standard)            
Pressure      29.92      inches of mercury (29.92 is standard)            
                       
Sg =      1.87                  

Dave,
My Miller program, gives a different out put.

This is what my Sg program says about that bullet and twist rate.

Frank

Here are some example of calculators not doing flat base bullets justice. JBM which uses the Miller formula and Berger bullets because they publish the specs needed for the calculator and recommended twist for each bullet.

These are both .243 Varmint bullets # 24313, 24321. Berger recommended twist is 1/12.

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Something that has a shape more like something that you could cast.

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150 grain .308 #30407, recommended twist 1/15

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That's why they don't recommend it for flat base

frnkeore wrote on Dec 17^th, 2018 at 3:34pm:


Another interesting thing to do with JBM is to check bullets with a plastic tip.

This is a 178 grain Hornady Amax with a plastic tip.
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Same bullet with the tip length at zero
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So clearly the shape and weight distribution have meaning when it comes to stability, but getting the accurate data points needed to predict it is difficult.

Variations of lube grooves in cast bullet at the back of the bullet, will play with the stability just as the plastic tip does in the front.

You can get an idea, but ultimately, you're going to have to shoot them. 

Not sure if this is still available but if anyone has an interest it would be hard to beat this price.

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JLouis

Also not sure if you received my last PM that might be of some help to you and if not please let me know and I would be more than happy to re-send.

Yes similar to Bennett's but I believe the nose forming die he uses is different. I think the big benefit is the lack of having the air pockets that can be cast into poured bullets creating unbalanced bullets. All the bases are flat, the edges sharp and probably more identically the same. A poured bullet shrinks after being poured and can shrink out of round. And there are no lube grooves to disrupt the air flow Dellet and he does quite well with them. The only thing I don't care for is I like a harder bullet and one of 1-16 tin and lead alloy. I feel it helps greatly to keep the unsupported spitzer nose from slumping off center from both shrinking in length to fill the grooves and the centrifugal forces being applied to it. In Mann's testing the X factor he could not eliminate was the lack of achieving perfectly balanced bullets. 

JLouis