Loading Based on Velocity Results

[Joe4d]

Normally the erratic velocity is above and below the book loads. The laws of physics dictates that more pressure will give more velocity. For every action, there is an equal and opposite reaction. Erratic velocity means erratic pressures, which indicates a problem, all the more reason to use a chronograph.

Not quite, more pressure doesnt equal more velocity. Look in a loadmanual,, Its more a pressure over time. I could load rounds that blow your gun up but barely launch the bullet, or fast bullets with low pressure.
Your gun will come apart due to an instant peak, Powder burns and pushes all the way down the barrel.
Thats why slow burning powders generally launch bullets faster at the same peak pressure.
So a slower burning powder with lower pressure peak, but it holds that peak longer,, or actually the pressure wave is flatter will result in more velocity.
Any time I have ever done a ladder.. ( same everythign just load 5 rounds of incrementally more powder) You usually have a sweet spot in Standard deviation, which generally means a more accurate load.
To light and I suspect its a case volume issue, usually the increase in velocity is pretty linear and a direct ratio,, as u get higher the velocity starts flattening out with increase in powder.
I suspect the pressure spike is increasing but not much velocity gain.. ur SD tends to fall apart around there as well.

 

[fredj338]

Hello... I've read about reloading for the 38spl/357mag and a consensus is that pressure signs aren't there until passed the safe pressure level and that loading based on velocity is the way to go. I'm sure that could also be applied to loading for 44 mag, which I'll be doing soon as I have a model 29 on the way.

After shooting 38's in my 357 I've decided I don't want to use 38 brass anymore, nor will I want to use 44 spl brass in the 44 mag. Will only be using the 357 or 44 mag brass.

That being said, I want to load "light target 38 loads" in a 357 case, light magnum loads, and I will also want to load up some heavy hitters for 357 sake. And the same for 44, some light medium and heavy loads all in the mag case.

Can a light 38 spl load (i.e the standard 2.7gr BE 148gr WC) be replicated into a 357 case?
Is it acceptable to load purely on velocity results?
What would be considered acceptable minimum and maximum velocity's in 357 and 44 for light target loads, and heavy but safe loads? (out of 6" barrels)
Bullets to be used for 357 would be campro's copper plated 158's, hard cast 158 SWC, hard cast 148 button nose WC. And for the 44, most likely a 240 plated and/or hard cast lead.

Well no. Vel variation can be enormous in revos. I have 5 diff 4" 357mags. They can vary as much as 125fps with identical loads. So trying to chase a given vel would certainly put me over pressure in one vs another. There are over pressure signs to watch for, like diff extraction or excessive case head pounding, all over pressure events, regardless of vel achieved.

 

[Wise_A]

Normally the erratic velocity is above and below the book loads. The laws of physics dictates that more pressure will give more velocity. For every action, there is an equal and opposite reaction. Erratic velocity means erratic pressures, which indicates a problem, all the more reason to use a chronograph.

Well, pressure doesn't create velocity, pressure over time does. You can have a high-pressure load with a fast-burning powder that generates less velocity than a lower-pressure load with a slower-burning powder.

The rest, you're agreeing with me. I'm not saying chronographs are dumb. I'm saying that it's dumb to load over max because your chrono results were lower than the book velocity for a load.

Perhaps you meant to say more or less the same thing, except whenever one starts mentioning "pressure = velocity", it's possible to interpret that as a license to go hog-wild if your gun doesn't duplicate the rather optimistic velocities listed in manuals.

What is a good reason to start shoveling powder in?

There really isn't one.

If the book says 15 grains at 1200 FPS, and without pressure signs I am getting 1400 FPS, should I be backing off? If I am getting 1000, is it not safe to up my charge?

If the book says 1200, and you're getting 1400, I'd be shocked. In fact, my first order of business would be to pull and weigh my bullets, verify the powder charge I'd dropped, and then check that my scale was working properly.

If the book says 1200 is the max, and you're getting 1000, no, it's not safe to continue. Your gun isn't going to explode if you go .1 grain over, but there's no percentage in pushing things, and the fact of the matter is that you really have no idea what's going on in the chamber.

What is a good approach to loading "off the books", and basing the charge on velocity?

I don't think there's any point to it unless you're in a few very specific forms of competition--and even then, I think those instances have been corrected-out by rules changes. There are so many cartridges and powders available, there's no sense pushing it. Another 100 or 150 fps isn't going to solve any real-world problems. I'd pick a different cartridge--either .41 or .44 Magnum, or .357 Remington Maximum.

Is there a method? Sure. Do I know it? You bet. Am I going to tell you how to do it? Christ, no. To be frank, the questions you're asking frighten me. Somebody mentioned to you something about loading based on velocity, and you've extrapolated that in entirely the wrong direction. You simply can't start exceeding book values until you correct that.

What velocity in a 357 is starting to get questionable? (low or high) For simplicity, base it off a 158 gr bullet.

Velocity isn't your limiting factor, erratic powder behavior is. I bet that I could blow up a gun with an overly-fast powder before I hit the maximum velocities achievable with a slower powder. And I can blow up a gun by jamming the bullet deep-enough into the case to spike pressures. And I can blow up a gun by loading it too long and jamming the bullet into the rifling. Similarly, just because I can hit X fps in my 6" 686, doesn't mean your 6" 686 will produce the same velocities. Even if we happened to have consecutive serial numbers.

Velocity means nothing. Average velocity means nothing. The relative consistency of five or even better, ten rounds means a lot.

The path you're asking about is dangerous, especially when you get into .44 Magnum. Things go very wrong very quickly when you get into big-bore Magnums.

 

[LoboGunLeather]

Learned the lesson many years ago. Everything I load is well below recommended "maximum" loads (9X19, .38 Spl, .357, .40S&W, .44 Spl, .44 mag, .45ACP, .44-40, .218 Bee, .25-20, .32-20, .300 Sav, .250 Sav, .308, .30-06, .33 Win, .45-70, .45-90, .45 Sharps Express, and a few others along the way).

Revolver ammo at 90% or so loads provides great practice ammo without undue strain on the gun. Magnum loads at 90% provide excellent performance within reasonable handgun range. Semi-auto pistol ammo only needs to consistently operate the pistol to provide good range service. Hunting ammo at about 90% loads provides excellent results on game animals at reasonable ranges. If I feel the need for more power I can simply change to a more powerful firearm, rather than try to stretch the capabilities of a less powerful caliber.

Works for me. I own several modern firearms from the past 50 years that have never been fired with factory ammo. I also have several 100-plus year old antiques that continue to provide fun at the range and critters for the dinner pot.

YMMV

 

[Protocall_Design]

Up to a point you are correct. It falls apart when your bore is of a different condition than the bore on a test gun. Take a well eroded rifle barrel that looks like a bad road. The friction from the eroded barrel will give less velocity than a smooth barrel at the same pressure.

If you only change one variable, the pressure, then you have the same equation. That means higher pressure in the same barrel. If you change from one barrel to another, you have a different equation and are not comparing apples to apples.

 

[rwsmith]

Hopefully....

Hopefully, one day in the future there will an affordable way for reloaders to measure their chamber pressures accurately.

Do you mind if I expound a bit?/

I'm not a mathematician, but I would think that the total area underneath the time/pressure curve would be total energy produced. If a powder can make this curve wider (longer time) WITHOUT exceeding the maximum pressure, it will have time to impart more velocity to the bullet. Is this right?

 

[Wise_A]

Yes. That's how powders of different speeds work. The number listed is the peak pressure. The manuals don't describe the duration of the pressure.

As per Hodgdon, .44 Magnum, 240-grain JHP:

Titegroup - 10 grains - 1292 fps - 37,700 CUP
HS-6 - 15.1 grains - 1417 fps - 38,200 CUP
Lil'Gun - 24.5 grains - 1582 fps - 38,100 CUP

Hence why slower powders tend to use larger charges. They're converting more mass to gas (et al), at the same peak pressure, by taking more time.

 

[BC38]

The bottom end of the charge range for most 38 special loads is about 10%v under max, and a 357 magnum case has about 10% more volume than a 38 special case (roughly).

In my experience, if you load at the top of the range for a given 38 special load - but in a 357 magnum case - your results should generally be in the same ballpark as what you'd get at the bottom end of the range using a 38 special case. Not exact, but reasonably close.

So, that is where I start when I load 38 special recipes in 357 magnum cases. Same for 44 special in a 44 magnum case. You can bet the power, pressure and velocity will be equal or a little higher than the minimum 38 special load, but WAY below a 357 magnum load for the same bullet