Home Forums Hunting & Shooting Ask The Gunwriters Using velocity to work up hand-loads

An open question to all but going to use JB in my example

I am getting back to reloading for a pair 7x57's. Stopped re-loading around 2013 or so when I got a CLR/NULA 30-06 that shot good enough with Fed Premium 180 NP's.

Reviewed my old notes, looking at left over ammo and started re-reading old references and looking at new references...looks like I had no idea what data I was really getting out of my chronograph or how bad that data could be!

One recommendation for working up safe handloads is to use the chronograph to measure velocity and then never exceed the book max velocity or the max charge for the powder selected.

In my past reloading, I typically hit the max powder charge first. However one of my 150 gr BT loads is probably warm given the velocities I was getting and the lack of consistent procedures I had for setting up my old Shooting Chrony.

How do you know when you are at the book max velocity with all the variables and measurement errors? Lets say the max velocity is 2753 but what is the +/- of that velocity. Doubt I would ever work up a load that averaged exactly 2753. When should I stop and say I'm at max velocity, +/- 50 or 100 fps, +/- 1 or 3%??? Just looking for some general guidelines for rifles.

Thanks

Scott

Not JB obviously.

When working up loads you will typically see steady increases in velocity for each increase in powder charge.

Let's say just for conversations sake you're seeing an increase of 50 fps for each .5 gr of powder.

At some point the increase in velocity will be much less for that same .5 grains.

That charge tells me I'm at or close to max.

That being said accuracy trumps all. I'm always willing to trade velocity for accuracy.

Hoping JB chimes in on this.

I disagree....Accuracy does not trump all. I will gladly trade a little accuracy for a little speed, and I will trade all of it for consistency.

If I have a 1/4" group at 3400, and a 3/8" group at 3510, give me the 3510 as long as the SD and ES are good to go.

What good are all those fancy numbers if you don't have accuracy ? Your theory would work for short range hunting I guess .

Your comments are examples of why I asked the questions...

What is the accuracy and precision of the chronograph and can I trust it to make decisions? Am I shooting enough rounds (3, 5, 10, 20, 50, 100???) over the chronograph with consistent procedures to trust the ES and SD to make decisions and to correlate with charge weights...

The more I've looked into the data I have, I know I didn't and couldn't in the past. I have a MagnetoSpeed so that should help with the chronograph issues but don't see how I would want to collect enough data for trust worthy statistics...

Need a good enough velocity range for some basic work...kinda like the bumpers they put of when you take your kids bowling...

I don't get the big push for a hundred or so F.P.S. If that makes or breaks your combo's ability to handle your situation, or intended situation, you should probably be looking for a lot more gun.

I’ll take the 100’ in place of 1/8” every day and twice on Sunday. How do you know it wasn’t 1/4” group as well. Guns shoot better than we can right???

So far much of this thread displays how little the average handloader understands statistics.

Jim Carmichel observed decades ago that many "pet loads" are determined from a single 3-shot group, which is statistically meaningless. These days they're also often determined by the standard deviation of a 3-shot string of chronograph velocities, which is equally meaningless.

But yes, a general velocity range of a handload provides some indication of pressure, when compared to pressure-tested data.

The question about how good is the measurement system is a good one, and one that not enough people ask. We just assume that our chronograph is giving us good data.

I've done a formal Measurement System Analysis on a pair of Shooting Chronys, and the precision isn't quite good to four significant figures. That last digit is plus or minus a couiple of FPS. So in that case, the precision is sufficient.

Accuracy is another issue. Speed is a derived unit of measure, based on a measurement of distance and time. The time base in a Shooting Chrony is a crystal controlled oscillator, which is probably good to around six significant figures, so no problem with time measurement. The limiting factor is the spacing and aiming of the photocells. Ken Oehler claimed that it was difficult to get the exact aiming down below 1/8" of error. Over the Shooting Chrony's 12" baseline, that's about 1%, which is still sufficient accuracy for practical purposes, a 28 FPS error at 2800 FPS.

So with the most basic of the chronographs, the precision and accuracy are sufficient. I've since switched to a LabRadar, and I expect that does even better. It's working off a Doppler shift system, and that eliminates the sensor spacing issue and reduces the problem to one of measuring the shifted frequency, which we can do with extreme precision and accuracy.

So the other question is whether we can work up loads using chronograph data. The answer is yes, we can.

Nyrifleman touched on an important factor. As you increase powder charge, muzzle velocity will usually increase in an orderly manner. But you can reach a point where additional powder starts to produce erratic results and velocity increases stall. You must be below this plateau point for the chronograph method to work.

If you are using the "book" specified components, and adjust your MV to compensate for any difference in barrel length, then if your MV is below "book" MV, your pressure is also under "book" pressure. OTOH, if you are using a "book" load and getting higher than "book" MV, then you have something like a tight chamber, short leade, etc., that is generating higher than desired pressure. Back off. Chamber geometry, brass thickness, etc. all drive pressure and pressure drives MV.

I really appreciate your posts Denton. Scientific!

A structural test engineer at work ( was a technician for this guy) had a shirt that read Rocket Surgeon, another that read Brain Scientist. Funny!

If you have QuickLoad and/or GRT (although GRT is generally not as good) and a good chrono, you can work out a fairly accurate relationship between pressure, velocity, and charge weight. At that point you can load to a reasonable max pressure for the cartridge and rifle without worrying about what an error-filled book says the charge weight that gets you there should be. Increasingly the data in manuals is just dry labbed from QL anyways, so the idea that it's somehow magically blessed is pretty funny.

If you find a charge weight where adding more powder increases velocity little or not at all, what you have found is an accuracy node.

Why you would want to load BELOW that, I have no idea unless you like wide spreads and worse accuracy.

This place is good for a frequent giggle

Thanks for the reply! What “velocity range” are you comfortable with when doing initial load work up in your rifles where you expect a MV around 2000 to 3000 fps?

If you are getting higher velocities than listed in the Manuel, I've found that you will also get higher velocities with factory loads than claimed by the manufacturer.

Is this unsafe? I'm of the belief that it is not necessarily unsafe, but maybe I'm wrong.

I couldn't agree more.

It will produce higher peak pressure than the manufacturer measured, assuming similar barrel length. Safety depends on how hot the manufacturer loaded the ammo.

So you think when Nosler puts out a loading manua0l it's just "dry labbed from QL" ?

Do you think when the Nosler manual states the most accurate load we tested it was just a lie ?

You would be better served to study some loading manuals and stop falling for all the internet bull.chit.

Barnes Vortex 140 TTSX in my 280 Rem with 24" barrel chronographs 3025 FPS over an Olher 35. Barnes claims 2980 FPS

The chamber has a tight neck and is still snug fitting to a bullet in the fired case. Definitely making more pressure than a rifle with a larger neck

Accuracy easily operates under the "good enough" theory. A slightly larger group that will keep me on steel or meat at range is more than "good enough," while the extra speed makes it easier to keep it there.

It's best to reference several different loading manuals....over the years I've owned/used about 6 or 7 different loading manuals in my opinion Nosler and Lyman are the two best.

I'll use the Nosler loading manual as an example. I load for velosity and accuracy....

So when picking a powder I look at the fasted loads they have listed for the weight bullet I'm interested in using.

Next I'm looking for the powders that are listed as most accurate at max charge.

It's a good starting point.

When the loading manuals says max pressure they are close....they tell you to start below max load for a reason.

Reason being in your gun max powder charge might be below the max charge they list....its pretty rare but it does happen.

Funny coindensce the cartridge I saw it happen with was a full custom 1909 Argentine Mauser in 7x57 Mauser.....no way you could get that gun close to max powder charge with out heavy bolt lift.