...but that BlammoCo SooperFang +P JHP self-defense bullet that's traveling 1100fps as measured at the box flap may only be averaging 1055fps as measured 8 feet from the 3.6" barrel of your carry pistol.
There was a joke back in the old muscle car days of the mid-to-late '60s, before the current SAE net horsepower rating standard was established, that "bhp" stood for "brochure horsepower".
In other news, join us as we ponder the question "How has a total nerd like me lived without a chronograph for so long?"
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Probably in an incomplete state. Not that you were aware of it or anything like that.
Reminds me, I need to get another one... sigh
"If you chrono your load once, you will know its velocity. If you measure it twice, you'll never be sure again."
I don't remember where I first read that, but there's truth in it. -- Lyle
Oh... Oh my gosh, yes.
A chronograph should be mandatory equipment for anyone that wants to call themselves a avid shooter.
Talk about valuable to a guy like me, that reloads his own rifle ammunition and shoots at ridiculously long ranges for fun... a couple hundred FPS can mean the difference between elk stew for dinner and an elk laughing his ass off at your poor marksmanship, because you shot 20 feet low.
Reloading manuals, for instance, lie their lying asses off on what you should expect for velocity out of a given case, head, and powder charge. To the tune of 250 fps or more... Heck, I've seen identical rounds shoot 150 fps different in a different rifle. Another thing you learn early on in the chronograph game - you load rounds specifically for each rifle. You don't make a round and then shoot it in everything, and expect it to behave the same.
Must have chronograph. Absolutely must have.
Temperature affects the burn rate of the powder. Higher ammo temperature make for a faster burn rate which means higher chamber pressure and thus higher velocity.
Want to bet that the test ammo is left next to the heater for a little while before being fired from a warm barrel so that a higher velocity can be recorded?
Al_in_Ottawa
Indeed. I don't use mine often but I find it invaluable data when I do.
They are the best tool I know of to test ammo for a specific gun. There are a ton of variables with each session with a crony. both anon and Goober are right. Temps and humidity do affect your .I hope you have a fun time playing with your new toy. And such a toy for us gun lunatics!!
Walt
Al in Ottawa: That's why the old timers I was squadded with in the CMP Western games told me to keep my ammo in the shade.
So, what are the recommendations for model?
I have a fairly low budget Chrony and made a spread sheet to calc the important stuff, Max, Min, Mean, StdDev, Energy (ft/lbs). I don't shoot just a couple of times, 10 is what I use for a decent, albeit small sampling.
Al_in_Ottawa:
Also, what length barrel was the factory test shot from? I seem to recall that 6" unported barrels are (or at least were) commonly used for manufatcurer's pistol caliber chrono tests. . .
I'm using the lo-bujit Chrony at the link (so far.) It'll do all the calculations for me. I'm using full 10-shot strings.
I started chronographing factory loads (and also my handloads) a few years ago. The most surprising result was that the 10mm Silvertips I tested, which are supposed to be rated at 1290fps for a 175gr bullet, didn't even make 1100 out of my G20, 10 shot average. Those were my carry load for many years.
Hornady's 180 grain XTP load, however, was nearly dead nuts on its advertised velocity, actually a couple fps higher IIRC.
Otherwise a 50fps loss seems to be typical from most manufacturers.
Any reloader that doesn't use a chrono is oblivious of what is really happening.
No biggie if loading bunny fart loads but when approaching max, you need to KNOW.
Some factory barrels shoot slow.
Some custom barrels shoot VERY fast - as in go above the midrange of the charge tables and you might have some in your face pressure problems.
Oooh, that version does the grab bag of stats?
My own cheapo chrony doesn't.
That's another interesting surprise, the velocity deviation some factory ammo has.
And that's not getting into the effect barrel length can have.
Chrons are great fun for nerding out on cartridges.
CHRONY ALL THE THINGS
I have the Shooting Chrony with the readout on a 20 foot phone cord ..... and good thing, too: the readout is apparently the spendy part ...... Shooting chrony replaced the body of mine for $30 when I ...... um, placed my projectile to be evaluated for velocity ...... a bit to close to the electric eyes ...... as in right through them .....
What caliber for Chrony? IME, .45ACP (230gr plated Ranier Ballistics HP @around 850 f/sec) does a bang-up job!
-jimbob86
Geodkyt -
I see, quite often, the "firearm used" is a single-shot such as a T/C Contender or Encore, 12" barrel, recording velocities for rounds normally fired in revolvers of 6" or shorter barrels. Less barrel length, add in a cylinder gap, and the loss in velocity can really start to add up.
Excuse me for saying this, because I've never had the chance to play with a crony, but isn't it a crappy design if they put the "brains" and display right below the spot where you shoot?
I keep hearing stories of people shooting their skyscreens by mistake.
Maybe you can weigh the whole thing down with a brake rotor or something that can double as armor plating?
(at least the price-point seems somewhat reasonable. Last time I priced 'em they started at $400 and tried to charge you an extra $60 for a serial cable)
-SM
Chronographs are simply a necessity for the serious shooter.
Another big factor affecting velocity is bore diameter. The worst offenders are found in the .38 cal/9mm handguns where I've found bore diameters as small as .351 and as large as .360.
Manufacturers will use 9mm tools in .38 caliber guns or .38 caliber tools to make 9mm barrels.
One of the most interesting things I've learned from my chronograph was how screamingly fast factory Remington .44 Mag 210gr SJHP were (sadly they quit making it years ago).
I ran the last six I owned across mine. I only recorded a 5 shot average because with the first shot I found the usual 5 feet from the muzzle measured nothing but muzzle blast.
They came in at an eye popping 1,470 out of my 6.5" 629 Classic when measured at 10 feet.
25gr of WW 296 only gets me to 1,242 using the same projectile and I'm not sure I want to try to push it any further.
Get a new hammer, and every problem looks a lot like a nail.
If we had unlimited supplies of ballistic gel instead of a new chrony, would velocity or penetration be our major interest?
"..but that BlammoCo SooperFang +P JHP self-defense bullet that's traveling 1100fps as measured at the box flap may only be averaging 1055fps as measured 8 feet from the 3.6" barrel of your carry pistol."
Base on that description, that difference in performance could very well be explained by the shorter 3.6 inch barrel instead of the 4.0 inch test barrel (5 inch for .45 Auto) used by the ammunition manufacturer and the 8 foot distance from the muzzle.
I like this site's data, especially the "real world" gun data:
http://www.ballisticsbytheinch.com/9luger.html
Despite what is printed on the box flap, manufacturers do describe that the bullet drops from gravity and slows down from drag as soon as it leaves the muzzle:
http://le.atk.com/ammunition/speer/handgun/
Seems one of my reloading manuals, Hornady? had a chapter "why ballisticians get gray" demonstrating variations in a single load of .357 Mag out of every weapon chambered for it in the factory. pretty impressive the differences a platform change will make all other things being equal. Even a change in primers can make all the difference in the world.
> What caliber for Chrony? IME, .45ACP
Piker. My brother put a 440 grain hard cast propelled by a .500 Smith through my first one. At least he still bought me a new one after I shamed him (with pictures) on TGC forum.
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