Velocity Question pertaining to 45-70

[Jeffery8mm]

This is really gonna sound strange, alot. I am trying to wrap my brain around this and am inlisting the opinions here.
Here is the question.
Is 1350 fps the same regardless of how you get to it??
Here is the senario
I can get 1350ish out of my 45-70 handi with a 405gr lee using 42gr +- of IMR4064 or 15gr of Unique
As long as I achieve 1350, it does not matter what powder I use does it??
One will not hit harder or fly flatter right??
I can shoot ALOT more using the unique loads.
Thanks
JEff

[crabo]

Velocity is speed, but accuracy and recoil may not be the same. I'm betting they won't be.

Some powders are going to launch the boolit better than others also, so X fps is only one part of the equation.

[paborn]

Same velocity, different powder with different burning rate (Unique 35)(IMR 4064 120), DIFFERENT PRESSURE. How did you determine the velocity? I would think the 15 grain of Unique with a cast 405 to be closer to 1200fps. I would expect the pistol powder to develop higher pressure quicker (burning curve). I use that combination as a plinker and find it is accurate to 300 yards, albiet with a 30 inch drop at 200, and a 100 inch drop at 300. How slow do IMR powders have to be for reduced loads not to be a good idea? 42 grains of 4064 is 90% of the lowest trapdoor load I can find in numerous manuals. I guess I'm wondering where the load came from as their are proven loads with IMR 3031, SR 4759, RL 7, H322, and many other powders more suitable for your purpose. Just my two cents for what it's worth YMMV

Paborn

[Catshooter]

Looking only at speed, it is what it is, doesn't matter how you get there.

Of course the 4064 load will give less pressure than the Unique, but, does it matter? Probably not.

I use 15 grains of Universal Clays on top of a 365 grain boolit for about 1365. UC and Unique are very close in burning rates. I use pistol primers and they show zero signs of pressure.

I love the UC load, it'll group right at an inch at 100 yards if I do my share and it's cheap!

Good luck.


Cat

[Bret4207]

Pressure curves will be way different. Both will develop about the same pressure since they both push the same wt boolit out the same length barrel to about the same speed. I may be wrong on that, but it makes sense since it takes a given amount of pressure (force) to move an object. But the longer pressure curve of the slower powder may alter that.......dang. We need Felix.

Which is the right answer O Wise and All Knowing Egghead???

Regardless, the different pressure curves may or may not do good things accuracy-wise. Try 'em and see which ya likes more bedder.

[btroj]

It may well be easier to get accuracy with the slower powder as pressure should be lower.
Seems to me it is a time to try different things and see what works. This is a prime example of a time to learn by doing. I find it to be the best way.

Please let us know what you find out if you try different loads.

Brad

[paborn]

Force imparted to the bullet is proportional to the area under the pressure curve. Unique will give higher peak pressure, IMR 4064 will give a lower peak pressure, but longer duration (area under the curve the same) if the velocities are the same. This is w hy slower powders develop higher velocities than fasster powders at the same peak pressure.

[Nrut]

No matter how you twist it, if Unique gives me the same accuracy/vel. in a safe load as IMR 4064 does, then it is Unique for me..
Another advantage that Unique has over IMR 4064 is that it flows a helluva lot better and throw's a more consistent charge thru my powder measure..

[Crusty Deary Ol'Coot]

Well, in all cases a load is not a load is not a load, in spite of the velocity figures being close.

A rifle is a rifle, but even with nearly identical makers, serial numbers etc. etc. they may or may not react the same with identical loadings.

So all that to say that, within reason and safety considerations the only way to really know how a combination of components will react in your rifle, is to shoot em.

Years back I was trying to develop loads for a son's 270 and not having a lot of luck.

Did the float the barrel and glasbed the action thing and although that cut groups in about half, it still didn't ring my bell.

A friend suggested I try a powder which I considered to be overly fast for the round and what do you know, bingo!!!!!!!!!! just what the doctor ordered.

Normaly I would have never tried that powder as my great wisdom said
it would never work. Hmmmmmmmmmmmmmm!

So, you have rec'd a bunch of good replies already, but providing you follow safe guide lines, it really comes down to how does it shoot in your gun.

Keep em coming!

Crusty Deary Ol'Coot

[Bob Busetti]

I have tried using small amounts of powder as Lyman liked to list a long time ago. I never liked using those loads because they always seemed to need a filler. Just me I guess. About the fastest powder I will use in the 45/70 in 2400, still needs a filler i.e. Grex or cornmeal.
When I had a large amount of H4831 on hand I would fill the case full enough so I could still
seat a 400 gr or 450 gr cast bullet.
Still, nothing wrong with it if it works for you. Good Luck with your shooting.

[fredj338]

I think pressures & pressure curves have a lot to do with cast bullet accuracy & leading. Fit is king, but matching pressures to your alloy seems to matter almost as much.

[HangFireW8]

Jeff,

This is really gonna sound strange, alot. I am trying to wrap my brain around this and am inlisting the opinions here.
Here is the question.
Is 1350 fps the same regardless of how you get to it??
Here is the senario
I can get 1350ish out of my 45-70 handi with a 405gr lee using 42gr +- of IMR4064 or 15gr of Unique
As long as I achieve 1350, it does not matter what powder I use does it??

This is actually a really good question.

It MAY matter. You may find the one powder creates less lead fouling than the other, because the initial pressure is different, and the time it takes for the boolit to obturate and seal the bore against blow-by differs.

Besides time-in-bore, the extra powder weight of the slower powder creates more recoil, because it is counted as ejecta along with boolit weight. Or, think of it as 27 extra grains of rocket fuel pushing against your shoulder.

That being said, the 45-70 is a very cast-bullet friendly cartridge.

One will not hit harder or fly flatter right??

Due to a different time-in-bore and recoil, one bullet may exit sooner while a slower powder may exit later, while the muzzle jump is in a different stage of progress, causing the trajectory to differ a bit. Essentially one powder will cause you to aim higher than the other.

I can shoot ALOT more using the unique loads.

That is a very common goal amongst cast boolit shooters.

-HF

[Bret4207]

Force imparted to the bullet is proportional to the area under the pressure curve. Unique will give higher peak pressure, IMR 4064 will give a lower peak pressure, but longer duration (area under the curve the same) if the velocities are the same. This is w hy slower powders develop higher velocities than fasster powders at the same peak pressure.

Okay, now that I've confused myself, let me see if what I'm thinking is right-

2 powders, same boolit, rifle, etc. Both powders achieve the same velocity despite large differences in pressure curve/burn rate. The pressure curve is different, but the energy produced is the same...right? My thinking is that to move e given object at a given speed the same energy is needed, correct?

Sincerely, Bret4207, who never took a physics class in his life....

[Cap'n Morgan]

If I run the powders through Quickload the numbers are as follow:

Unique:
Bullet travel at Pmax = 0.63" (the distance the bullet has moved when pressure peaks)
Pressure rise time = 0.384 ms (the time for the pressure to reach it's peak)

IMR 4064:
Bullet travel at Pmax = 0.93"
Pressure rise time = 0.535 ms

Obviously you'll get a more 'gentle' acceleration with the slower powder. The Unique will be "all-burnt" after the bullet has moved only 1.7" where as the IMR will only burn approx 70% of the load in a twenty inch barrel.

Whether it's worth burning almost trice the amount of powder to achieve a less steep pressure curve is up to you and your rifle.

[btroj]

In the end it is personal preference. It comes down to what you, and your rifle, seem to like best.
I would rather use 2400 for loads in that velocity range but that is my own preference- no science behind it.
While either will work I would say this- try bother and see what the rifle prefers. That should be the ultimate deciding factor. Every rifle is a unique entity and has likes and dislikes- find what your wants and give it what it wants, you will never be disappointed this way.

Good luck.

[Crusty Deary Ol'Coot]

Yep btroj,

It seems like I read that same basic info back a few posts.

It can be fun to "what if" and "how do you think this will work" and a bunch of other spectulations/questions, -----------

But you are totally correct, in the end it comes down to what you and probably more importantly, what your rifle likes.

Now to arrive at certain goals, you may choose to shoot a less then perfect load for your rifle's likes and best proformance, so be it, your choice, but as already said, your rifle will tell you what it likes.

Keep em coming!

Crusty Deary Ol'Coot

[Dave B]

Once it leaves the bbl, I can't see how it got up to speed would make a difference. Recoil might give it a little different trajectory, but other than that, I don't see it.

[btroj]

That is true Dave, to a point. The key is what shape is it in when it leave the barrel. If the pressure was too high for the alloy/barrel fit/lube combination it could be very different than when all is well.
To me the key with cast is what happens in the barrel rather than once it leaves the barrel. Pressure can be a huge factor here.

[MtGun44]

Since powder is sold by the pound, I would go with the Unique if it provided the accy and
lack of leading you need. Why spend a bunch more money on propellant if you don't need
to? Now if the harder acceleration that the Unique is providing is causing some sort of a
problem, then try 2400, which is slower than Unique but faster than 4064.

Bill

[thx997303]

15 gr of Unique is a highly accurate load in my Guide gun.

However, I am unsure whether you will actually get 1300 fps with the 405 gr boolit.

I get 1300 fps with 15 gr under my 350 gr ranch dog boolits.