45-70 2 loads with unexpected results. I need some input.

[crackerjack57]

I went to the range last night shooting my 45-70 expecting to get one result but getting quite another. was wondering if some of you might of done some work with these loads and could explain why these results showed up. on both loads im using 65 gn of 2F compressed with a milk carton wad separating the powder from the bullet. both loads shoot very accurate but when i but all the verified data in several ballistics programs, the results for the 500 grain load are exactly as the programs state however for the 396 grain bullet they are not even close. i will add a picture below with the trajectory but here are the details to work with.
Gun: H&R 45-70 buffalo classic
lighter bullet: NOE 460-396-RF PB AE2 .2777 BCE 1310 FPS
heavier bullet: Lee 459-500-3R .443 BCE 1200 FPS
both are loaded with 65 gn of 2F compressed.

I am zeroed at 220 yards and both loads are accurate. what i was trying to achieve was a flatter shooting load then the 500 grain greaser for hunting at the longer ranges and something that had a bit of meplat on the front. any insight to help me understand why i got these results instead of the ballistics program results would be appreciated. also if any of you have insight on what i might expect down range at 300, 400 and 500 yards would be appreciated as i dont think the ballistics programs will be right. I was clearly expecting the 396 grain NOE bullet to shoot flatter not the opposite.

Heres my drawing.
243755

Thanx for your help.

Dan

[17nut]

Given bullet weights, as you described the bullets, then they have the same speed at 200m.
From there on the light bullet is slower and will drop like a stone with the poorer BC.

What ballistic programs gives wrong data and what are these wrong data?

I use Ballistic Basics 7.5 and that is usually spot on (given the correct BC).
It shows a height at 100m for the 500gr @ 41cm and the 396gr @ 37cm.
I suspect you typed something in wrong in the used calculator!

[crackerjack57]

I already thought that i might of typed something wrong and went over my ballistics calculator several times. I have 2 ballistics calculators on my iphone. one is called bulletdrop+ and the other BulletflightL1. for the Bulletdrop app, the 500 gn at 100 m or 110 yards gives me 13" or 33 cm the other app gives me 15.6" or 39 cm. my actual is about 16" or 40.5 cm so very close. its the 396 grainer that has me stumped. putting in all the proper info from the mould manufacturer and getting the speed from my chronograph, the measurement is still out. on the first ballistics program it says 14.2" or 36 cm and the other 14.8" or 37.5 cm which are very close to what you have also so my information is input the same as what you have. where the problem comes in is that the trajectory of the lighter bullet is higher at the 100M or 110 yards then what im expecting. real world numbers are 24" or 61 cm high at the middle mark. so 9-10" higher then what i was expecting.

[17nut]

If mid range trajectory is as you describe then speed is way off, has to be.
If i dial it down to 1050fps then i get 24" at 100m with a 200m zero.
The only other way is to set BC to .1 and that's no way near a 400gr bullet of any sort.

[crackerjack57]

If mid range trajectory is as you describe then speed is way off, has to be.
If i dial it down to 1050fps then i get 24" at 100m with a 200m zero.
The only other way is to set BC to .1 and that's no way near a 400gr bullet of any sort.

I hear ya and that thought didn’t even come to mind as the speed is verified by 6 separate shots all reading 1310-1330 FPS. The exact same powder load pushes a 500 grainer to 1200 FPS. I’m thinking that the manufacturer may have his BC a little off. I also would find it hard to believe that it could be that low though.

[John in PA]

Is the midrange trajectory measured or calculated? A bullet with double the ballistic coefficient will easily retain velocity and therefor shoot flatter AT RANGE than the design with substantially more drag. If the ballistic coefficients are accurate, then I believe the results you posted above. And, if yoiu calculate the muzzle energies for both loads, I bet the 500 grain bullet is more efficient (more ME) too.

[Chill Wills]

Bc is dynamic. Very much so when working with in the transonic range. This might be described in your case as 1400 FPS dropping in the course of flight to <900FPS.
So... No one Bc fits the bullet to plug into the program.

Something to understand about these 45 BP type rifles. They carry their energy well even at long range. However, making hits on game at longer ranges comes down to knowing the distance exactly and being able to set the sights exactly. Really, past a 200-250y at starts getting unfair to the game.

Have fun!

[crackerjack57]

the question was asked if the midpoint or 110 yard trajectory was measured or calculated. the 24" rise is actual and where it should be according to the ballistics program is about 14.2"

heres where confusion comes in. your comment of no one BC fits a bullet. why would we then have a BC if it really doesn't mean much??

[country gent]

There are several online free programs that will calculate BC for a given bullet The big information you need is velocity at 2 distances preferably from the same shot. Muzzle and 100yds 200 is better. This will give you a very accurate bc to work with and produce a trajectory table.

Heavier bullets carry energy and velocity better my load with a 550 grainer is 1230 at the muzzle and still around 1050 or so at 200 yds ( this is from memory) Lighter bullets don't fair nearly as well and just getting above super sonic can introduce other issues.

Some BCs are on the generous side, actual velocity can affect the BC. Its not uncommon to see bcs for a given bullet in velocity ranges. Getting the numbers and calculating the BC works for me.

[waksupi]

Something to keep in mind. If you already have an accurate load, you will need to add 300 fps to appreciably flatten a trajectory. And then not by much. Then you are back to searching for an accurate load again. Better off staying with your most accurate load. I intentionally keep my .45-70's below the speed of sound to avoid midrange transition.

[greenjoytj]

Just to make a point as to the variability of ballistic coefficient.
For example a Sierra .458” caliber 300 grain jacketed HP flat nose bullet, SD .204
From the Sierra web site, see the BC change with velocity:
.120 @ 2400 fps and above
.145 between 2400 and 1900 fps
.185 between 1900 and 1400 fps
.210 between 1400 and 1150 fps
.230 @ 1150 fps and below

I do not know how much the group size would altered/expanded as the bullet slows to less than the speed of sound. But I would experiment with trying to load up the MV so my bullet stays super sonic all the way to my intended game range. I don’t know it this kind of MV is possible with BP.
Bullet alloy strength would surly come into play but if the bullet is too hard it may not expand reliably at long range. Good luck with your experimentation.