Originally Posted by Varminator 911
So you must be near a BC of 1 to surpass the 265 and 280 338 bullets. Are we talking that high? If so, I may be ordering a 308 8 twist as you suggest. Also, what is the length of that 220?
BTW an estimated BC is all I want. Won't hold anyones feet to the fire over an estimate.
There are some rules of thumb (again rules of thumb and not statistically proven theorems or postulates) we developed when testing and anticipating the performance of the .338s and the .30s.
--The first one was that the 300 SMK and the 265 grain aluminum tip were within .010" in length. The advertised sea level BC of the SMK is .768 and the calculated value (based on velocities) of the 265s was .770. Fairly close and fairly accurate rule of thumb...... Like profiled bullets of the same length should yield close BCs. Nothing new here.
--The next rule of thumb again involves around Sierra bullets. The .338 250 grain SMK and the .30 240 grain SMK. They are the same length and their sea level BC difference is .124. So for for bullets the same length with like profile geometry but changing the diameter from .338 to .308, you get a boost of .124 in BC. Again, these are Sierra bullet values and the noses on these aluminum tips are more slippery and uniform.
--Last thumb rule we will discuss is that on the aluminum tipped .338s we achieved a relationship of .1 BC change for a .1 change in length. This should be more in a .30 caliber since the frontal diameter is less.
--So, the 212 .30 caliber bullets are the exact same length as the 300 SMK and the 220 is .056" longer than the 212.
You can do the math for these sea level calculations and come up with what we believe is a very conservative BC since the profiles of the Henson bullets are more aerodynamic than the SMKs.
The main reason for the hold up on getting the BC information is that we broke a Nightforce NXS 12-42x56 scope. I don't want to disturb/seperate other scope rifle combinations that are set up. Secondly, my wife had surgery yesterday for a foot reconstruction and we had to get some things done prior to the surgery and I am unavailble at this time to conduct the BC testing (playing nurse). Should be done soon after that Nightforce scope gets here. I would think it will be by Wednesday/Thursday (if the weather cooperates).
In review, 212 advertised is mid .8xx and the 220 advertised is high .8xx low .9xx. I feel we are very very conservative on the BC numbers in the discussions we have had. No one gains when performance claims are inflated. I think we have a good chance to be north of the above numbers. However, I feel we have left evough wiggle room in case all the previously proven rules go bust.
When you run the above numbers at .30 velocities in comparison to the .338s at their velocities, it is impressive.
I don't know what the BC is for the Wildcat 265gr .30s, but I am confident based on measurments that the 220 grain Henson should eclipse it.
Who knows, but it is fun to speculate and perform testing.
Finally, do not order any barrels based on our testing until we get the final .30 cal 220 grain BC hammered out and published. Just start hiding piggy banks in preparation for the order.
One other point, when we are measuring bullets (both the Henson variety and the others), we noted that the others had more of a deviation from bullet to bullet than the aluminum tipped Henson product. This is probably due to multiple dies being used for manufacture. A major goal (since we are all long range fans) was to minimize the deviations in BC from bullet to bullet. All the Henson bullets are made on one set of dies for that caliber. It really does minimize dimensional variations.
We are not trying to be non professional by putting out the information as it becomes available vice waiting until all the testing is complete as other companies do. We know hunting season is around the corner and we are trying to get the bullets ready and tested for those who wish to use them this season in their own firearms. We are avid hunters and we understand what hunters want and when they want it.
We are trying to support your interests and desires.