Can bullet BC be better at Subsonic ?

[Blancoalex]

Is it possible for a bullet's BC be better at Subsonic speeds. I ask because with very limited testing so far I have to increase my BC in app to match my impacts. Bullet I am working with so far requires a 30% increase. OR is something else happening that I am missing?

Thanks

 

[Plinker147]

No, BC goes down as speed goes down. If your having to increase BC that much something else isn't inputted correctly. Be sure your using g7 type apps for g7 BC. I've always found it better to adjust velocity than BC since most of us have no real way of measuring what the BC is for our conditions and individual rifles. I wouldn't adjust BC more than 5ish% percent.

 

[Blancoalex]

I am currently using Flat base pointed spitzer bullet. Not able to find a g7 for it. Only Nolser's g1 , isn't g7 usually around half of g1?

 

[ShtrRdy]

Well, BC is a multiplier to the Drag Coefficient curve for the representative bullet. You've likely seen BC number for a G1 or a G7 ? The G1 BC best matches a bullet shape that has a flat bottom and a shorter nose/ogive. The G7 BC best matches a bullet shape that has a boat tail on the aft end and a long slender nose shape up front.

Are you firing these bullets at subsonic velocity? Or is the bullet flying through the trans-sonic regime?

 

[Blancoalex]

These are starting at Subsonic (1140) . I am going down a unusual rabbit trail to see how far out(LR) I can be precise. For now this just for the fun of it. Not much info about Subsonic long range other than cast bullets.

 

[ShtrRdy]

It sounds like G1 would be the better choice since it's a flat base bullet.

Since BC is a function of velocity I would go ahead and choose a BC that gives you what you're seeing. You need a good measure of velocity and the scope to bore distance.

 

[Blancoalex]

Jus t found Shooter Calculator it gives adjusted bc using my station conditions. You start with factory g1 and it converts to little higher bc.
normal SP for me is 28.4 +\- few each direction.
temperature shows a big spread when going from 29F to 89F. Wonder if I should consider using g6 . Will try more testing to hopefully to find working compromise.