Observations - velocity, OAL, etc

[38SPL HV]

Checking my records, a 158 gr swc 38-44 load (38 Spl cases) under 11.0 grs 2400 and 1.465 OAL gave me a average velocity of 1,053 FPS. The same charge of 11.0 grs using the heavier 358429 Keith 170 gr SWC in 357 Magnum cases seated to crimp over its driver band (1.545 OAL) gave me an average of 1,136 FPS.

These measurements were off a LabRadar with the same Ruger 4 5/8 inch Blackhawk, the same day!

All proving that one must always pay attention to your reloading manual and start low, and if you have the resources, use a chronograph.

 

[308 Scout]

I've found that when loading cast bullets, minor changes in bullet weights doesn't make much difference in velocities, but hoe deep the bullet is seated does.

I was recently loading some cast 230 gr. RN's for my 1917using the universal 1.27" o.a.l. My velocities were quite a bit lower than I expected. What I found was due to the profile of this particular bullet, it needed to be seated deeper in the case. Once the bullet was seated to the point that it used as much powder space as other 230 gr. bullets, expected velocities were achieved.

How much bullet is in the case is far more important than how much is out.

308S

 

[gwpercle]

You would "think" the lighter bullet would be faster under the same powder charge . But the variables are the bullet weights , bullet lengths , case lengths and seating depths...
With that many variables it's not surprising the results were different .
Can't assume anything in reloading...gotta test it out .
Gary

 

[ruggyh]

In addition to Gary's post/list above, bullet material and bullet bearing surface play a important role. As he stated

Can't assume anything in reloading...

be safe
Ruggy

 

[Rule3]

Which is why heavier bullets generally have a lighter charge plus stuffing a heavier bullet deeper into the case raises your pressure therefore your velocity
If it was s super fast powder in less of a gun you may have had a BIG problem!

 

[38SPL HV]

You would "think" the lighter bullet would be faster under the same powder charge . But the variables are the bullet weights , bullet lengths , case lengths and seating depths...
With that many variables it's not surprising the results were different .
Can't assume anything in reloading...gotta test it out .
Gary

Exactly my friend

With the velocity I'm obtaining with the 170 gr Keith SWC and the very good accuracy, this is fast becoming my standard magnum load. It's velocity (1,136 FPS avg) in the 4 5/8 inch Ruger BH duplicates the velocity of the lighter Federal 357 Magnum 158 gr JSPs, with the added benefit of the heavier Keith 358429.

 

[38SPL HV]

Which is why heavier bullets generally have a lighter charge plus stuffing a heavier bullet deeper into the case raises your pressure therefore your velocity
If it was s super fast powder in less of a gun you may have had a BIG problem!

Learned this when staring out reloading in 1970s...and proven over the chronograph. Rule3 made sure I learned that the truth is over the chrony...it took some perservance on his part due to my stubborn German nature and the fact when living back East we were precluded from having chronographs at the indoor ranges.

Thanks again Rule3

 

[ruggyh]

Which is why heavier bullets generally have a lighter charge plus stuffing a heavier bullet deeper into the case raises your pressure therefore your velocity
If it was s super fast powder in less of a gun you may have had a BIG problem!

Velocity is not increased by pressure, it is a function of pressure under the curve.

If this was the case, you could determine peak pressure from velocity.

be safe
Ruggy

 

[Rule3]

Velocity is not increased by pressure, it is a function of pressure under the curve.

If this was the case, you could determine peak pressure from velocity.

be safe
Ruggy

A function of pressure is still pressure

If you have the same bullet for two different loads and one has more powder which will increase pressure than will you not have more velocity? Yes there is a curve but it is all in the equation.

Set your sights on pistol reloading data | Hodgdon Reloading

Winchester 231
.357"
1.455"

3.8
661
12,600 CUP


4.3
779
15,900 CUP

So let see with the above

3.8 grains gives 661 fps and 12,600 cup

4.3 gr gives 779 fps and 15,900 cup

So the higher pressure yields a higher velocity
Call it what you want more gas in the same confined space yields more pressure yields more velocity.

 

[ruggyh]

A function of pressure is still pressure[/B]

Yes pressure is pressure but pressure is not velocity

In your first statement

Which is why heavier bullets generally have a lighter charge plus stuffing a heavier bullet deeper into the case raises your pressure therefore your velocity
If it was s super fast powder in less of a gun you may have had a BIG problem!

Seating any bullet deeper increase the peak pressure, with out regard to weight, this is a function of case fill, not bullet weight.

While a heavier bullet weight will contribute to peak pressure, it is because the bearing area is increase and the moment of inertia is greater.

If you have the same bullet for two different loads and one has more powder which will increase pressure than will you not have more velocity? Yes there is a curve but it is all in the equation.

This not what you said in you first statement and is only true if the case fill is greater in the case with the increase powder. This assumes the same seating depth.
If the seating depth is the same would could expect an increase in both peak pressure and velocity.

If I keep the case fill the same by seating the bullet in the case with more powder, the peak pressure would be the same but the velocity would increase. By doing this we would have increase the pressure under the curve and hence in creased the velocity without increasing the peak pressure, more velocity with same pressure!!!

Set your sights on pistol reloading data | Hodgdon Reloading

Winchester 231
.357"
1.455"

3.8
661
12,600 CUP


4.3
779
15,900 CUP

So let see with the above

3.8 grains gives 661 fps and 12,600 cup

4.3 gr gives 779 fps and 15,900 cup

So the higher pressure yields a higher velocity
Call it what you want more gas in the same confined space yields more pressure yields more velocity.

This would be as expected, all the rules as I called out above are demonstrated in this example. You have presented two very different examples.

Same cartridge, same bullet, and same seating depth.

You increased the case fill and increase the both the peak pressure and pressure under the curve. The Pressure under the curve is moved by not one but two reason in this case volume increase in powder and increase in pressure.

If you do a little more review of you data you will find that many different powders with same bullet and same seating depth at the same peak pressure produce different velocities, and in some case much lower pressure and clearly higher velocity.

Easy to see that peak pressure doesn't equate to same velocity.
If you think this because the charge weights are higher were velocity is higher, this will not be the case in most (this is a topic for a different thread).

be safe
Ruggy