Thoughts on Velocity

[ET]

In some of my spare time with no range access yet because of this pandemic I’ve given some thought-on velocity. Have to give the brain some exercise during this slow period. Eventually I will be crossing that path of boosting velocity for some given loads. Higher velocity reduces the ballistic curve and extends the range of the bullet. With the advent of all copper bullets higher velocity is beneficial and usable. By pressure I’m referring to the pressure curve developed. Peak pressure doesn’t dictate the final velocity result. The amount of pressure remaining, reaching the muzzle also influences final velocity result. IMO this includes both sabot and sabot-less shooting.

Through observing different pressure traces done by TG I believe I can formulate a concept of what transpires. To start with is the Rise Time for achieving load velocity at peak pressure. I believe the faster the rise time the higher the velocity will be at peak pressure. For continued load acceleration the rate of dropping pressure and remaining pressure to the muzzle will dictate the final resulting velocity. For now, this is theoretical but a starting point.

The first thing needed is a good ignition source. Not ruling out duplex.
The second thing needed is a specific load resistance to hold the bullet load stationary to develop a good level of pressure for the start of the accelerated burn.
Then a slower pressure drop from peak pressure with a certain level of remaining pressure reaching the muzzle.
Sounds simple right, chuckle?

So now it’s time to choose a bullet weight and powder candidate to see what velocity can be obtained using above parameters. I’m a little way off for velocity testing but have a direction to go when the time comes. I enjoy putting a theory together and then see if it pans out or if I’m full of you know what, chuckle.

[cuda]

The Barnes 290gr .451 TEZ all copper might be a good starter.

[ET]

Aug 4, 2020 16:30:06 GMT -5 cuda said:

The Barnes 290gr .451 TEZ all copper might be a good starter.

This is one time I have to disagree with your choice, chuckle.
The direction I’m going to start with is 4198 and 250gr bullet. Here I have some load references for comparison. Also, I want to begin in familiar territory gaining some experience before venturing elsewhere.
My theory is based on the principle of bullet acceleration is the amount of pressure applied behind it. That also has to take in account the rate of pressure applied. The faster the pressure build up behind the bullet the more acceleration has to occur resulting with higher velocity at peak pressure. I think of this as the jump point before the down hill run with remaining pressure.
Now after the jump point as the pressure drops so does the rate of the bullets acceleration. By lessening the rate of pressure drop we get more bullet acceleration. Hence the use of slower burning powders.

The catch here is how to stimulate the slower powder for a faster pressure build up (burn) for a shorter Rise Time. One answer seen so far is using a duplex powder load.
Not to bore anyone with further thoughts on the subject I will end here for now.

[cuda]

They make it in a 250gr .451 TEZ. My son is shooting the 290gr TEZ with a lubed wad and 69grs of IMR4198. It is a Stevens 200 with a 45cal barrel on it from Luke.

[ET]

Aug 5, 2020 7:56:40 GMT -5 cuda said:

They make it in a 250gr .451 TEZ.

Now that I do have on hand.

[edge]

Do you have a specific velocity goal?

edge.

[ET]

Aug 6, 2020 10:55:44 GMT -5 edge said:

Do you have a specific velocity goal?

edge.

Good question. For the 250 bullet I would like to see at least 2800fps for the all copper bullet.
Now I’m prepared to move my redline of 40K to 45K if needed as the barrel can easily handle that pressure. Also, I plan to use the faster developed load for hunting only. For range practice less shoulder pounding loads will be more comfortable, chuckle.
If 4198 doesn’t give me what I seek with certain parameters then I will move to Reloader10. The results from PT testing will direct me to what direction I need to go.
This will be my most interesting project with the 50.

Ed

[ET]

One obstacle after another. I was hoping to eventually start my velocity testing with acquiring 4198 for future preparation of testing but nobody has any in stock. I do have some of the longer grain 4198 but not enough to run a proper test. Okay plan B.
Reloder 7 is my next best option. Here I have the bonus of a reference trace TG made.
2450fps, peak pressure of 32K, and a Slower Rise Time of 130-160. From 2450fps to 2800fps isn’t a long hop with plenty of peak pressure to work with, chuckle. Here too by adjusting the Rise Time I’ll see if my theory has any merit. Just hope Reloder 7 is readily available.


I also like the grain configuration of Reloder 7.


Ed

[jims]

Each area varies on powder it seems. There is plenty at my gunshop in Ohio but primers are nearly non existent.

[ET]

Aug 12, 2020 7:10:40 GMT -5 jims said:

Each area varies on powder it seems. There is plenty at my gunshop in Ohio but primers are nearly non existent.

It's ironic that you have a primer shortage whereas up here primers galore. But powders we have a real shortage. If I find 2lbs of reloder7 it's mine bought and paid for. I see a lot of potential with reloder7 even for other loads. Okay I'm not there for velocity testing but when I arrive I want supplies on hand.