Your opion on this

[dirtdobber47]

Using the same bullet,brass and primmers ,but different powders, velosity is the same through a crony, how will it effect trajectory?  Using the same rifle.  Thanks   :roll:

[leverfan]

If you're using the same bullet, launched at the same velocity, the trajectory will be identical.  Accuracy may differ, though.  That's something that you'd find out during bench testing as you develope the loads.

[Idaho_Hick]

Two projectiles of identical B.C's, launched at identical angles and identical velocities, will have identical trajectories, regardless of any other variable.

[John Traveler1]

NOT quite true!

Using an extreme example of a medium or large black powder case (.38-55, 32-40, .45-90, .45-90, etc), you can shoot BP loads and then equivalent velocity smokeless loads ato VERY different points of impact, points of aim, and with small but measurable trajectory differences.  It has to do with "ejecta mass" or the different densities of different powders.  Accuracy (grouping ability) will naturally be affected.

[Graybeard]

When you change powder all bets are off as to what results you'll get. Same velocity aside. That bullet might land in same hole or up to 6" or more away. Been there done that. Change powder and you change barrel harmonics.

I used to do a lot of such testing while running them over the chrono. I've changed powders using all esle same and gotten same velocity but wide diparity in bullet impact on target. And I've had them land in same group. You just cannot know until you shoot them.

[ricciardelli]

As I have stated in another forum, you change barrel harmonics when you change powders, and the POI will be different.

[Idaho_Hick]

I thought my reply was properly qualified by stating that the two projectiles had to be launched at the same angle.  Obviously point of impact changes, but this is due to the barrel harmonics previously mentioned.  If your barrel weebles instead of wobbling at the instant of projectile exit, then you will not have identical launching angles.  

I think maybe I thought too hard on this one and gave the physics answer, when others were thinking of the practical application, which is of course that the rifle has to be re-sighted in.  However, once that rifle is sighted in with the new load with the same projectile and velocity, the trajectory will be the same.  For example, if you were previously sighted in dead on at 200 yards and were 2 inches high at 100 and 8 inches low at 300, then once you sight in your new load of identical velocity for 200 yards, the other figures will still apply.  I apologize for any confusion.

[dirtdobber47]

Thanks a lot guys, I agree that poi could change. I think I won the disagrement with my buddy. Didn't I?