New .224 cal from Arsenal

[rintafile]

hopefully groups like those in the picture, I still do not know what that caliber would be... Maybe I'm too ambitious 

If You are ready to put some hard cold cash on barrel there is always change to get good results....

[rkr]

Yes, I saw that.... The only way is to test to actually measure the BC, but somewhere between 0.112-0.157 seems likely.... Using the SD for a GC bullet is often close for the BC at our velocities, which is right in the middle at 0.134.... If we look at the velocity at 100 yards, starting at 950 fps, a BC of 0.11 gives 825 fps, ad a BC of 0.15 gives 854 fps.... so there is not really a big difference.... By comparison, a pellet with a BC of 0.04 would only be going 672 fps at 100 yds.... 

Bob

Not much difference in speed but it's wind drift I'm interested about.

If we take a typical 5 m/s wind at 90 degrees then drift at 100 yards according to chairgun is:

BC 0.11 = 4.94" drift
BC 0.15 = 3.67" drift

Now if we take a 50 grain 225450 bullet from NOE with claimed 0.2 BC we get:

BC 0.2 = 2.78" drift

Still, it's accuracy that counts - you can always learn to read the wind they say. Now I really need to get my .224 BSA project started

Slainte, Riku 

[rsterne]

You are correct, BC is far more important to wind drift than velocity or trajectory.... However, calculated BCs are only a approximation, and without knowing the velocity and algorithms the calculator is using, they aren't good enough to calculate drift, IMO.... It takes actual measurements at airgun velocities to know for sure.... The 225450 is a Spire Point bullet, and while that design has a significantly lower BC when Supersonic, the difference between it and a bullet with a moderate Meplat in the Subsonic and low Transonic region is much less....

I ran the 225450 through the Kolbe calculators.... It tells me that it needs a 12" twist because of the extreme 0.660" length for a 48 gr. bullet.... and it predicts a BC of 0.17 from Mach 0.5-1.0.... The same calculator predicts a BC for the new Arsenal bullet of 0.15 at Mach 0.5 to 0.16 at Mach 1.0.... not a lot less.... At Mach 2, the Spire Point really shines by comparison.... The Arsenal bullet BC is 0.12, while the 225450 is 0.18.... Fortunately, we don't care what happens Supersonic.... 

Bob

[rsterne]

My mold is ready and will ship to Erik at HP Mold Services, along with a 6mm version, tomorrow....



Bob

[tronickero]

My mold is ready and will ship to Erik at HP Mold Services, along with a 6mm version, tomorrow....



Bob

Wow looks really good the mold, I await see the performance in your hayabusa.

Tron