Will the same boolit at the same velocity but a different powder have different POI?

[44Blam]

I'm going to answer my own question in a couple days, but I have two loads that yield a similar velocity.
The cartridge is 45-70 and the boolit is a NOE 460-350 RF and I cast them with a cup point. They are gas check'd and PC'd. And they end up weighing in right at 335-337 grain.

The two loads are varget and H335 and they end up sending that boolit right around 1900 fps in my Marlin 1895 with the 20" barrel. That rifle also has a Montana #101 sight on it...

The H335 load recoil impulse is a little snappier while the varget load impulse is a little smoother.

I've done some long range DOPE with the H335 load where I've been able to record the MOA measurements out to 625 yards. I'm kind of curious if the speed of the powder burn at the same boolit velocity will affect the POI at all...

Here are the contenders:
286153

[Texas by God]

The answer is in your rifles barrel. Maybe they will, maybe they won't. The wonderful unpredictability of ballistics is afoot. Please let us know how it does.

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[Mr_Sheesh]

Same thought here, if the barrel resonates differently (More amplitude from a sharper impulse) it would potentially change POI. But it depends on timing of the whip, could be zero difference if you are lucky. Curious what your results will be!

[762 shooter]

If it were lighter bullet I would guess maybe.

With a 45 70 cannonball, my guess would be same POI.
762

[Shanghai Jack]

Agree with Sheesh. We want repeatable harmonics and want the bullet to exit the barrel at the same precise location along the harmonic curve so that each bullet enters the same hole.. Different powder charges, different seating depths, different powders, land engagement, yada yada yada . . . would all seem to impact the barrel harmonics.

Not sure I understand where 762 shooter is coming from. Let's ignore harmonics for the moment. What happens if you fire a projectile perfectly parallel to the surface and and at the same time the bullet exits the bore, you drop the same bullet from muzzle height? They hit the ground at the same time. Gravity is immutable. F(net)=(m)(a)

That having been said:
whether a bullet is traveling 2 feet per second or 2000 feet per second in the horizontal direction it still falls at approximately 9.8meters (32 feet) per second squared in the vertical direction
whether a bullet weighs 20 grains or 200 grains, it still falls at approximately 9.8 meters per second squared in the vertical direction.
Reference the legendary alleged Tower of Pisa cannonball experiment.

[charlie b]

And don't forget the effect of recoil. A 'sharper' recoil pulse will make the barrel move a bit different than a 'softer' recoil pulse, resulting in slightly different muzzle position when the bullet leaves the barrel.

[William Yanda]

Jack, I dispute your assertion. I was not a whiz in Physics, but it seems to me that you are discounting the time required for the fired bullet to reach it's peak. Assuming that you meant similar projectiles, not "the same" for I am sure that you will agree that it is impossible for one object to be in two places at the same time.

[Conditor22]

If you look in the Lyman CB loading manual, they highlight the best/most accurate load for each boolit and list the fps. there are several other powders with comparable fps.

There has to be a reason the one they highlighted is better.

I'm more of a basic/non-technical reloader. I look at BHN and not alloy content, groups on paper, not chrono fps, function over style/looks .....

[dverna]

Even if they hit the same POI in your trial, one event is not enough proof to make a general statement.

[remshooter]

my 30-06 when i used , remington cases ,remington primers ,and remington bullets ,loaded to same velocity as factory remington ammo exactly the same but the powder ,.Cant know what powder remeington used ,,would hit 3 inches lower ,than factory remington ammo. Everytime i tried doing that

[remshooter]

my 30-06 when i used , remington cases ,remington primers ,and remington bullets of the same weight as factory ,loaded to same velocity, as factory remington ammo exactly the same but the powder ,.Cant know what powder remington used ,,would hit 3 inches lower ,than factory remington ammo. Everytime i tried doing that

[rbuck351]

There are so many variables that a same poi would just be luck of the draw.

[oley55]

with absolutely no intent to ridicule, but expecting/hoping for the same POI is just about as naive as my past posts and attempts to find loads/cast bullets that would perform equally well in my revolvers and rifles. Try though I did, that dog just wouldn't hunt, at least not yet...

[Dieselhorses]

I deleted my post earlier but I’m gonna say it anyway. Slower burning powders need heavier crimps. Faster burning powders not so much. Adjust the crimp and that’s the ticket to POI.


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[Shanghai Jack]

Jack, I dispute your assertion. I was not a whiz in Physics, but it seems to me that you are discounting the time required for the fired bullet to reach it's peak. Assuming that you meant similar projectiles, not "the same" for I am sure that you will agree that it is impossible for one object to be in two places at the same time.

Yes the identical bullet, not the same bullet. As for the time to reach its peak, I shouldn't take my medicine before I post. Perfectly parallel to the surface. Thanks for catching that error

[Shanghai Jack]

I deleted my post earlier but I’m gonna say it anyway. Slower burning powders need heavier crimps. Faster burning powders not so much. Adjust the crimp and that’s the ticket to POI.


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And another interesting point - it would be interesting to play with the crimp as well, changing the crimp incrementally and seeing what happens. Neat thought Diesel.

[Shanghai Jack]

I deleted my post earlier but I’m gonna say it anyway. Slower burning powders need heavier crimps. Faster burning powders not so much. Adjust the crimp and that’s the ticket to POI.


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And another interesting point - it would be interesting to play with the crimp as well, changing the crimp incrementally and seeing what happens. Neat thought Diesel.

[Shanghai Jack]

I am mostly a breach-seater. I remember reading some reloading notes from the Schuetzen era. One author sought to test the effect of bullet indexing on POI. He cast as close to identical bullets as possible, each with an index mark indicating its original orientation in the mold. Then after mounting the rifle in a shooting vice, the bullet was seated in the chamber with the index mark at he 12 O'clock position and fired. The next was seated with the index mark at the 1 o'clock position and so on. The claim was that an accurate rifle could be forced to shoot a generally circular pattern on the target as a result of unseen minute variables in the mold concentricity. Anyone remember who it might have been. Maybe Pope,Rowland or Hubalek. When my wife lets me retire again this summer, I may give this a shot.

[mr surveyor]

Jack, I dispute your assertion. I was not a whiz in Physics, but it seems to me that you are discounting the time required for the fired bullet to reach it's peak. Assuming that you meant similar projectiles, not "the same" for I am sure that you will agree that it is impossible for one object to be in two places at the same time.


I have to ask .... what do you mean by "fired bullet to reach it's peak"?

Just asking


jd

[charlie b]

It means that a different bullet path means a different peak of trajectory.

Shanghai, I think it was Pope who did the indexing thing, along with testing bullets deformed in different ways.

[Shanghai Jack]

I have to ask .... what do you mean by "fired bullet to reach it's peak"?

Just asking


jdWill

I initially said perpendicular instead of parallel - William identified it and I corrected itl

[William Yanda]

Yes the identical bullet, not the same bullet. As for the time to reach its peak, I shouldn't take my medicine before I post. Perfectly parallel to the surface. Thanks for catching that error

Now that changes things. LOL I read your original post literally, didn't think about the similar situation oriented 90 degrees differently.

[Cosmic_Charlie]

Pistol barrels are short and rigid compared to most rifle barrels. Yet, different powders do deliver different results. I have always thought that the pressure curve was the cause, how fast the boolit is forced into the rifling and it's rate of acceleration down the barrel. This is pure speculation though.