Originally Posted by Jon A
I think taking this as a fact is helping to skew your hopes and dreams the wrong way.
I do agree with the Berger being conservative for how we think of BC's. If you measure at high velocity (close to the muzzle) you should get a higher G1 BC. In fact, you can see this by plugging in their G7 number of .323 and converting that to a G1 with an average velocity of 3000 fps (which would be typical if measured over 200 yds from a 300 RUM) and it comes out to a G1 of .656 (using the JBM converter). That's only a hair higher than I measured the 210 SMK by using that method but lower than the 208 A-Max.
You are making an error which is understandable. Do not use manufacturer supplied BC specifications for your estimates. Two of the companies you mentioned are good on this kind of reporting, the other is not... you are relying too heavily on the one that is not.
Jon and Noel
I agree that some BC #'s are questionable. In fact, I look at ALL BC #'s with a grain of salt )sometimes a shaker of salt) after reading the many threads in this forum. Some are probably more accurate than others and I see all of them as starting point of reference.
A number of things can affect BC in a single type and weight of bullet, probably the most significant being velocity. Typically, higher MV's produce higher BC's in a bullet, and as the bullet flies down range, the BC usually deteriorates.
Michael reported testing the 208 Amax (listed BC of .648) with a BC of .671 and another member, MT300RUM reported a BC of .6443
1200yd culligan water jug shot..
I dont doubt any of the BC reports for the Amax bullet, and take each for face value with a grain of salt. There are a number of reasons that the BC's may differ, including possible errors in data. There may have been no errors in data and the differences may be purely enviromental and/or differing velocities, etc.
On the mentioned bullets I used for a relative refference, the 180 E-Tip probably has a fairly relaible BC and I read one post where a forum member tested them to be just about right on. At what velocity and range, I don't know. The overall lengths differ by .110, 1.47 vs 1.58, the noses differ by ~.12, ~.7 vs .82, and the tail of the E-Tip very roughly "appears" to be about half the length of the 177. The only BC edge for the E-Tip is a pointy poly tip vs the unknown HP meplat of the 177. I see those differences as fairly significant, maybe enought to account for about a .07-.08 difference in BC?
With the 210 Berger, the OAL is 1.484, .096 shorter than the 177, the tails "appear" to be the same and the noses are the same except the Berger has a smaller meplat. So with essentially the same tail/nose length and more mass and a smaller meplat the Berger certainly would have a better BC, but by how much and is it's BC actually conservative relative to other bullet BCs? I have read several posts from members saying the old BC's worked spot on for them.
The HATs are definitely more of an unknown commodity. They have been advertized to be greater than .7 and I have not seen anything posted to dispute that, nor confirm it. The HAT tail is slightly longer than the Berger, maybe .003? And the nose is .002 longer than the Berger and the overall length is .091 longer than the Berger, so shape wise it is more BC freindly, but the Berger has more mass. Hmmmm....
Based on all this, I still believe the 177 could possibly have a BC of .6, especially if fired at speeds in excess of 3500 fps, and the fact that it's design boosts its velocity over that of similar weight bullets actually also boosts its BC, a factor we haven't really considered.
Anyway, I am hoping to give them a try in my 300 RUM as soon as I can get some, which probly wont be until early fall. When I do, I will also shoot them against the 210 Bergers for grins. That should be interesting.
Congrats on your ZA50/6.0-M tests. Hopefully these results will bode well for your other projectiles.
Also, If you can develop a 195 gr pill with a BC in the upper .6's I think you should a good advantage over the other current offerings. I think the upper velocity limit needs to be higher than the 338 though.