Friday, September 27, 2013

Perfect Timing - a Day at Camp Chronograph

There's a lot of good information in various reloading manuals as to how much powder to put in a particular reload. But like anything where humans are involved, there can be a lot of "hit or miss" as well, especially in manufacturer's claims as to the velocity of a load in your gun.


Because they did the measurements with THEIR gun. NOT yours. Variations in bore smoothness, chamber dimensions, throat shape, headspace and other factors make your firearm unique, even if your buddy next to you is shooting the exact same make and model of firearm (maybe it's just me but I seemed to notice that 9 mm round bore diameters vary wildly between manufactuers).

Finally, be especially careful with near maximum loads; never assume that because a maximum load is safe in one gun that it will be safe in others.
Knowing the velocity of your loads allows you to refine them for the best possible accuracy at distance as well as removes the guesswork from holdover while insuring optimum bullet performance on game.

I'll be honest. I knew almost nothing about such things when I was new at reloading.Reloading isn't just for the self sufficient crowd. Many folks are finding that reloading not only saves them money per round but I've found that carefully assembled handloads will almost always yield more consistent velocities than commercial ammunition.  If you're going to reload though, the chronograph, as nifty as it is, wouldn't be my first purchase. Frankly for me, then, and even post Chronograph, my favorite reference for reloading is my well worn  Lyman manual. But the information from the chronograph is not just interesting it IS useful.

I have seen several chronographs since then and I can tell you, when it comes to buying the equipment, there IS a difference. Many of the chronographs are manufactured overseas. They are cheaper.

But as my Dad always told me, you get what you pay for.

The Brand in use here is the PACT one. The brand was a friend's recommendation, after owning a couple of them. There are several good chronograph brands out there, such as the Shooting Chrony Alpha, which, for my friends up North who shoot, keeps Canadian Jobs in Canada.  This isn't a product you want to go for cheap (but babe, if I get the Sam's Club Chronograph, I get a free camo snuggee!) Certainly PACT could make them overseas and cheaper, but they choose not to, and the quality is evident (not to mention keeping jobs at home for Americans as well).

In addition, you don't have to have a CSI ballistic lab to measure bullet velocity, all you need is a good quality chronograph. And unlike a TV CSI, you don't have to carry your gear around while wearing a $800 suit, solving all crimes in an hour, all the while looking like a supermodel.
I had four bags of "test" rounds to start with (three pictured) Two bag were Missouri Bullet Company bullets (a company I've had great service from) with different powder loads. Two bags were Roger's Better Bullets (a gift from a friend) also with different loads. All the ones I tried were .45 acp.

Why a Chronograph?
In simple, the velocity of a given round is a byproduct of the average pressure in that round. Simply put, velocity is the speed of the bullet. There is no free lunch here folks. Velocity reflects pressure and velocity and pressure translate into performance and safety for the reloader. If you compare the actual velocity of a particular charge to the predicated velocity you can determine if you're getting adequate ignition or if you are rapidly approaching the "Danger Will Robinson" zone on pressure even if you are below the "maximum" recommended load.

Taking One for the Team:
Being a chronograph is not without its risks. Chronographs are, by their very function, constantly in the line of fire when in use. They're positioned downrange, and most shooters will manage to nail at least one chronograph sometime in their years of use. I've been lucky and just winged a support arm once, for which cheap replacements are usually on hand. But because it is necessary to shoot between the supports and the diffuser on a chronograph, inaccurate shooting can readily lead to a bullet going through the chronograph instead of the empty space which it monitors for speeding bullets. Outside of taking a job as a target stand, there's not many jobs at the range riskier than that of the chronograph.For that reason, it's not a toy. I wouldn't let a new shooter have a go at it, unless you have a couple hundred dollars laying around you want to get rid of.

For this night's adventure, we wanted to see if recent reloading was measuring up to speed for match performance, or should just be kept on hand for practice. It only takes a small variance in shot to shot velocity to make the difference between a load that goes "bang", and one that goes "Wow"

How they work is really pretty simple. Just like the opposite sex, you can usually manage to operate one even if you don't have a clue as to how they actually work. They are however, VERY sensitive devices and need to be handled with a little care (also like the opposite sex). The chronograph contains an extremely high-speed digital clock that starts running the instant you turn the chronograph on. This internal clock generates millions of quick pulses that are needed to calculate the speed of your bullet.

Most photo switches are mounted on this type of device, and it's their job to signal the chronograph when your bullet passes overhead. The first photo switch is activated by the shadow of the bullet passing overhead, and it signals the unit to "begin time" (counting the clock pulses). When second photo switch sees the bullet it signals the unit to stop counting the pulses.
Simple in theory but pretty amazing if you consider just how quickly and with what accuracy, these photo switches have to react. When the number of clock pulses is captured, the chronograph immediately and easily calculates and displays the exact speed of your round with a little microprocessor chip

It's a simple formula

velocity = distance/time
In this case, the average feet per second for a magazine from one bag was about 795.. It should have been a little higher, so these rounds for my P220 likely needed just a bit more powder. The round ejected quite nicely though, and accuracy was good.

But a higher velocity is not necessarily a good thing. For most shooting applications the accuracy is more important then the max velocity. If you gain 100 to 200 feet per second in most rifle cartridges, neither you or the target are likely to notice. For hunters, trajectory changes due to these small velocity increases are usually so small as to not really make a difference, and reloading for higher accuracy may even degrade accuracy. In a pistol load, intended for competition we might wish to fine tune them a little more. Why the chronograph is even more important.

But although velocity is what we are looking at here, it's relationship to pressure is just as important, not just for accuracy but for safety. Pressure does the work to move the bullet through the barrel and on to Mr. Target (if Mr. Target would quit MOVING around!)
If the pressure is too low, the bullet could stick in the bore or fail to generate enough velocity to do the intended task (sorry dear, I'm just tired tonight). If the pressure is too high, not only could your fine firearm be damaged, but there is a genuine risk for injury.

I'm not going to get in any greater detail here. I'm a beginner and I'm sure I have a few readers who are as well. If you want to read an excellent discussion of velocity variations, pick up a Speer Reloading Manual for Rifle and Pistol and check out "Why Ballisticians Get Gray" in the handgun section.

In the meantime, if you are getting serious about reloading or just want to check out the accuracy of those rounds you are depending on, consider a Chronograph. Add a couple of patient friends and a few bags of your favorite rounds and fire when ready.
When you're done and home, you can compare your notes, recalculate what you wish to do next time and for myself anyway, worry about that one thing that all the supermodel forensic scientists on TV worry about.

Which of my favorite bath products remove GSR the best?