Ordered today for the C Sharps that should arrive real soon (I hope). 

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As a rule Accurates turn around time is pretty quick.They do make very nice molds.  When you get it, if you ordered the aluminum mold blocks, give is a nice bath, dry it well and then use a butane lighter or one of the ones for lighting a gas grill and give the inside a good coat of carbon and that mold will quickly start to cast good bullest. Yea it makes that nice shiny mold look kind of nasty but I have yet to have an aluminum mold cast well without  that coat of carbon on the inside.
Sam

Red Cent - you may want to consider this Accurate mold also ...
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It is the clone of the Ideal 375166 bullet, that in a 1:18 twist calculates to 17.65 for the Greenhill black powder rating.
100yds 
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200yds
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300yds
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The bullet needs to be the right length to obtain the best spin of the bullet. 
The gyroscopic stability (Sg) is dependent mainly on bullet length and barrel twist. The accurate bullet you specified is: 

Caliber      0.378      Inches            
Bullet Weight      310      Grains            
Bullet Length      1.16      Inches            
Barrel Twist      20      Inches/turn            
muzzle velocity      1250      fps            
Temperature      50      degrees Fahrenheit (59 is standard)            
Pressure      29.92      inches of mercury (29.92 is standard)            
                       
Sg =      1.44                  

Caliber      0.378      Inches            
Bullet Weight      310      Grains            
Bullet Length      1.16      Inches            
Barrel Twist      18      Inches/turn            
muzzle velocity      1250      fps            
Temperature      50      degrees Fahrenheit (59 is standard)            
Pressure      29.92      inches of mercury (29.92 is standard)            
                       
Sg =      1.78      
           
Caliber      0.378      Inches            
Bullet Weight      310      Grains            
Bullet Length      1.16      Inches            
Barrel Twist      16      Inches/turn            
muzzle velocity      1250      fps            
Temperature      50      degrees Fahrenheit (59 is standard)            
Pressure      29.92      inches of mercury (29.92 is standard)            
                       
Sg =      2.26                  
           
                       
Sg shouldn't be less than 1.4. Not enough spin and the bullet will tumble. Using a shorter bullet will increase the Sg.

If Sg is greater than about 2.0 you are overspinning the bullet; you may gain some accuracy by going to a slower twist barrel or using a longer bullet.

So you need to confirm the twist of your barrel and the groove-to-groove diameter.            

The bullet base band has to be at least the same diameter as the groove-to groove diameter of your barrel.
However you can easily use bullets where the base band is .001" to .002" wider than the groove-to-groove diameter.

I always use molds .002" wider to obtain a tight fit since it helps prevent gas cutting around the edge of the bullet.            
You have ordered a tapered bullet which is great for barrels with no/or little chamber leade.

However if you have a long and/or wider chamber leade then a straight bullet with equal driving bands may be more suitable to prevent bullet runout before it goes down the tube.

C Sharps Hi Wall w single set trigger and PG stock. Custom bedding.
Green Mountain barrel 30" full octagon #4
14:1 twist
groove .376
Monatana Vintage Arms  Winchester “B” Series Scope with No.2 Mount
If this is redundant, bear with me. The chamber specs match this:

In my experience, overspinning the bullet definitely is the lesser of evils, if an evil at all:  I've gotten stellar accuracy with bullets sopposedly  too short for the ROT of rifles.
Meaning I'll prefer anytime to have a twist that's a bit faster over a slower one - the alternative is a bullet that's unstable, which definitely is MUCH worse...  And it also will limit usable  bullet selction, whereas a faster twist  doesn't.

I'm with Joe and MB on this one. While the rifle was obviously set up to shoot heavier bullets in the 38-55 for BPCR, it should do just fine with the somewhat lighter one. My 16 twist 40-65 shoots 400 grainers for BPCR and 285 grainers for 200 meters with no complaints while my 18 twist 40-60 Maynard did not like the 400s (as might be expected) but thrives on 370s.

The bullet can be ran through a .377 sizer. I could have Tom reduce the base but I will try the bullet in my Marlin 336. .379 groove but that heavy bullet should bump up fine with BP. Who knows. John Boy uses an awfully heavy bullet in a 1:18 twist with success. 
And I do plan to get another mold. Or three. Maybe this one increasing the driving bands to .377.
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John Boy, will keep that one in mind.