More questions for the Experienced

[BuckeyeWally]

I have some questions that the old-timers could help with:

1. What are the dynamics describing the relationship for a given caliber between bullet weight, powder type (slow/fast and any additional variables that I am unaware of), primer (doesn't it just have to energize the powder or is there more to it than that?).

2. when you measure the velocity of a bullet with a Chroney, what are you looking for beyond consistency? Is it a slower bullet or a faster one, consistency in speed or something else? Why?

3. What are your measurement strategies (assuming you have a chroney) in fine tuning and/or evaluating a new round?

I am sure these are the start of many questions. Many thanks.

[603Country]

Those are big general questions, but I'll have a go, but keep it basic.

- buy a Lyman 49th reloading manual. It will give you general info on bullets, powder, etc.
- low intensity cartridges (think 30/30) will use fast burning powders
- high intensity rounds (think 257 Weatherby) will use slow powders

The primer ignites the powder. Gotta have a primer. As for the powder to use, the Lyman book will give you that info, and what range of powder charge.

My measurement is based on accuracy, not velocity or consistency of velocity. You don't need a chrono.

I hope that helps.

[big al hunter]

I agree with 603 Country and will add to it. The primer needs to ignite all of the powder consistently. So use the recommendations for primer for each powder, from your loading manual. Consistent powder charges, consistent ignition and consistent bullets provide...you guessed it, consistent accuracy. There are other factors. Some barrels won't shoot some bullets worth a hoot. Some barrels like any bullet you throw at 'em.

Some folks use the chronograph for measuring consistency. Most that I know use the velocity as one of the markers for over or under pressure. There is no such thing as a free lunch. Higher velocity than the manual could mean more pressure. It is a safety tool. It is not the only, or best way to determine pressure, but it is more obvious than some of the other methods. It will also help calculate trajectory if you wish to shoot long range. Other than that they are extra. I don't use one.

[Beepy]

1. What are the dynamics describing the relationship for a given caliber between bullet weight, powder type (slow/fast and any additional variables that I am unaware of), primer (doesn't it just have to energize the powder or is there more to it than that?). I'll try to provide you an answer based on general principles only:
Generally, the less overbore of a cartridge and the lighter the bullet, the "faster" the burning rate of the powder. That is generally speaking only. Use the manuals for specific loading information. For instance, a .45-70 with a light for caliber bullet will use a much faster burning powder like IMR 4064, where the Remington 7mm Magnum with a 175 grain bullet might be loaded with Retumbo or H1000. Again, follow the manual at all times.

A primer's job is actually two fold: #1= Light the powder. #2=Light the powder with enough force to provide complete and reliable ignition.
#1 = standard pistol or standard rifle primers for the average task. Magnum primers should be used for magnum loads and hard to ignite powders such as ball powders. (Win. 748 and Win. 760 come immediately to mind.) Always use the type and brand of primer called out in the manual for the application you are loading for.

2. when you measure the velocity of a bullet with a Chroney, what are you looking for beyond consistency? Is it a slower bullet or a faster one, consistency in speed or something else? Something else, is my answer. My purpose is to be sure I am not exceeding the velocities that I should be by more than a little bit. I am also wanting to see if the load is as consistent as my target says it is. Why? If I am getting velocities much faster than the manual says I should, it is a very good indication my pressures are exceeding what they should be and if I am near the maximum listed load, then I am probably exceeding the safe pressure levels for that cartridge which means I will back off to safe levels. Not only do I not want to have a gun blow up, feeding a gun a constant diet of maximum loaded cartridges is like driving your car with your foot on the floor all the time. Not a good practice if you want longevity.

3. What are your measurement strategies (assuming you have a chroney) in fine tuning and/or evaluating a new round? See # 2 above.
Also, a chronograph is helpful in providing information. During development of test loads, my favorite method is to load 3 rounds of each 1/2 grain increment increase in powder, always starting with the manual starting load. If during the course of fire from starting load to maximum load there is a sudden significant increase in velocity - greater than anticipated or that the book says it should be - I stop immediately. Such is an indication of excessive pressures. Also, if your velocities vary widely in any particular recipe - be it powder, primer or bullet - I'll usually make note of it in my log and move on to something else. That saves me a lot of time and money spent on components. If your rifle doesn't like a load, it will show up on the chronograph. A good example is my Remington 788 carbine in .308 Win. In defiance of all that is holy, it will not shoot BLC(2) worth a hoot regardless of bullet or primer. It shows on the chrono stats, too. Extreme spreads well over 100 fps are common and standard deviation less than 40fps are rare, and even more rarely repeatable.

I hope this is helpful

[BuckeyeWally]

Outstanding Beepy - Just what I was looking for. Thank you all for sharing your experience.

[wogpotter]

2. when you measure the velocity of a bullet with a Chroney, what are you looking for beyond consistency? Is it a slower bullet or a faster one, consistency in speed or something else? Why?

Several things.

Consistency:
Usually you want each round to have very similar ballistics to the one before & the one behind it. This is where things like spread (fastest minus slowest), variability (Standard Deviation) is the difference between any 2 successive rounds comes into play.

Pressure:
Pressure & velocity are interconnected if the pressure is high so is the velocity & so on.

Powder suitability:
A "good" powder will be very close to estimated velocity every time you fire it. Powders that "jump" or fall too low or too high, or have a large variation round to round are not as "good" (for that particular load).

Safety:
If your 900 FPS load suddenly is giving 1500 FPS then you've done something wrong, (such as using the wrong powder, or wrong amount of it, by accident!)

3. What are your measurement strategies (assuming you have a chroney) in fine tuning and/or evaluating a new round?

Calculate the "ideal starting load" from a manual or by comparing several manuals. Fire a few (5 is plenty) round with that load & compare the chrony results (see above) to see how your individual gun likes or dislikes the load. Now look for accuracy. Is this load really accurate in your individual gun? (they all have preferences, even "identical" models.)
Make a set of slightly different loads one "lght by a small percentage, one "by the book" & another slightly hotter (but never exceeding the book max. Fire all 3 sets & see if there's an improvement with one or another. Pick the best result & fine tune it again with a closer set of High, Low, Normal.

[WaltherRuger]

I think a chrono is very valuable.
Due to differences that you may not be aware of (seating depth, bullet type), you may get much different results than published data.

Although velocity is not the same thing as pressure...............
If you get 1130 fps when the published data says 1050, you know that you're also getting higher pressure then the published data, which is important if you're near the high end of the published data. It may be that you've seated the bullet deeper than the round used in the data.

Also, I do pay attention to Standard Deviation. If I am shooting rounds with an average of 1050 fps, and my standard deviation is small, say 7. Then I know that I don't need to be too concerned that I may get a round that has much higher velocity (and pressure) that could cause problems.

[TimSr]

Pressure & velocity are interconnected if the pressure is high so is the velocity & so on.

If you get 1130 fps when the published data says 1050, you know that you're also getting higher pressure then the published data, which is important if you're near the high end of the published data.

I disagree with the general assertion that higher velocity equals higher pressure.

Our concerns with pressure are with PEAK pressure, where our reactions in velocity are more related to the length of duration of the pressure.

When we get 1300 fps from a 6" .44 magnum revolver but get 1600 from the same round in a rifle, does it mean the same round created higher pressure in the rifle or was it the duration of the same amount of pressure?

Why is it that you can't get nearly as high velocity from your magnums with fast powders as you can with slow magnum powders, even though max chamber pressure for both powders is the same?

For that matter, there are cases where overpressures can result in a reduction of velocity.

A Chrony can show when thinsg are totally out of whack with reality, and they can show inconcistancies that you can't see in other ways, but if your velocities are above published test data in a non-drastic way, it's a lot more likely to be difference in their test components and yours.

[wogpotter]

I disagree with the general assertion that higher velocity equals higher pressure.

Please re-read the "safety" part of my post.
When I say pressure & velocity are interconnected, there's the assumption that the same gun is being used.

[gman3]

Big case-little hole=slow powder...generally speaking

[Jeffm004]

I would add that the shorter the barrel, the faster the powder. Generally.

[jmr40]

I would add that the shorter the barrel, the faster the powder. Generally.

No!

The powder that proves to be fastest will be the fastest regardless of barrel length. All powders burn within just a few inches, slower powders may need an extra inch or so, but all completely burn in any barrel long enough to be legal. Longer barrels are slightly faster because the pressure of the burning powder has more time to accelerate the bullet before it leaves the muzzle.

Start shooting 300 WM from 6" barrels and there may be something to this myth.

To answer your questions you 1st have to determine what you plan to do with the bullet after it leaves the muzzle.

Are you going to hunt with it? If so, what game, and how far do you plan on shooting? How much recoil are you willing to tolerate? Are you just going to shoot at targets? And once again at what range?

Slower burning powders generally give better speeds, faster powders can be sightly more accurate. Powders that are considered slow in one cartridge may be too fast to be optimal in another. The bullet type and weight is determined by the game hunted.

It is also a factor in target shooting. Flat based bullets at slower speeds are often very accurate at 100 yards or so, but perform poorly at longer ranges.

Bullet shape is huge. Some bullets are far more aerodynamic than others. A bullet with poor aerodynamics may be 100 fps slower at 200 yards than a bullet with excellent aerodynamics even though it started 500 fps faster.

[Sevens]

I think there is one important facet of a primer that has been (thus far) left out. In addition to the obvious jobs that it does, a less obvious but still extremely important job it has is to be a safe stop-gap for pressure.

This is most obvious in a few well defined roles-- such as .454 Casull, .460/.500 S&W Magnum. Places where the cartridges develop a max working pressure beyond (or FAR beyond!) what is "typical." It's also why we use small rifle primers in .30 Carbine amd .327 Federal Magnum.

As for the chrono, I am not a huge fan which seems to put me at odds with most who own them. I handloaded phenomenal ammo for 20yrs before buying a chrono. What do I need it for? I load 15-20k rounds a year and I am certain I do NOT need it.

What do I use it for? Curiosity. Admittedly, I think it is far more useful for a rifleman estimating bullet drop over a distance. But it's always going to be my staunch position that it's nowhere in the hemisphere of "necessary" to make safe, fantastic handloads.