Hurray, Chrono worked!

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berettaprofessor

berettaprofessor

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First day with my Alpha Master Chrono...worked perfectly on around 70 rounds except for the last two (err) which I chalked up to it getting too far into the evening/dark. A couple of questions:

1) Out of a Beretta PX4, it was reading Federal 115gr 9mm FMJ at 1152 f/s, a little faster than the box rating of 1125 f/s. Is the difference because this Chrony reads slightly fast, or likely normal variation because of the particular gun or the cool temps (54F)? Standard deviation was like 5.5 f/s so it was pretty consistent

2) I tried several rounds out of a S&W 638 snubby. All rounds were well under their advertised or predicted speeds. Is that just the byproduct of shooting through a snubby versus a 4 inch or longer revolver?

For anyone's interest, particularly those who are low on traditional powders, 4.0 grains of Trail Boss behind a 230 LRN averaged 620 f/s. 5.5 grains of 7625 behind the same bullet was 696 f/s.

Oh yeah, and I didn't shoot the Chrono :)
 
The difference between 1152 and 1125 fps is not really a difference. Forget it.

Yes, you will get lower velocities out of a snubby.

230 LRN speeds in the 600s are a bit too slow for me. Sometimes can get poor functioning and/or poor accuracy at those low speeds. How did they work for you?
 
It's always a good day when the chrono DOESN'T get shot! Your speeds from the PX4 and the snubbie seem about right.
 
Chronos are cool and a great tool.
I would say just remember the vel shown is for your chrono on that day at that time. Different day, same ammo your chrono (or another one) might read a little different.

Walkalong showed how not to reset one here

http://www.thehighroad.org/showthread.php?t=733530
#19

:what: :eek: :uhoh: :)
Shorter barrel = lower vel
Listed vel for any ammo seldom matches what you will get in your firearm.

Temp, humidity, wind etc can all make a difference. 1125 vs 1154 close enough.
 
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The low speeds of the 45 ACP are on purpose; I wanted some soft loads so the SR 7625, 5.5 gr is loaded to the minimum that kept it functional in my Taurus and Colt. And I'd tried the Trail Boss at 4.5 and 4.0...and maybe 5; book isn't nearby to check. Anyway the loads at 4.0 make one 5-shot hole at 7 yards offhand behind a 230LRN....fairly regularly. At 4.5 they spread out a bit. Got the targets to prove it. Anyway, at those levels, both guns function fine. I've shot over 50 of each and no squibs with either load.
 
Yeah, DukeDog, saw that one. I also saw somebodys shot up picture of a Chrono here a few days or week ago. Yikes. I was nervous the whole time I was shooting. After Chronoing 70 rounds, I know what Walkalong means about not getting in a hurry.
 
1) Out of a Beretta PX4, it was reading Federal 115gr 9mm FMJ at 1152 f/s, a little faster than the box rating of 1125 f/s. Is the difference because this Chrony reads slightly fast, or likely normal variation because of the particular gun or the cool temps (54F)? Standard deviation was like 5.5 f/s so it was pretty consistent
Click to expand...

Load manual speed is not even shot out of a pistol. It's measured out of a machine made to specs listed (for pistols usually 4" bbls) that measures pressures and other info given.

If your pistol's rifled bbl is longer/shorter, a different type of rifling, bore is bigger/smaller, rifling is more/less per inch, the temp/elevation at the chrono is different, the brass was thicker/thinner/longer/shorter, then the results will be a little off from the manuals speed. If every one of these was measurably different, then it could be off quite a lot.

Your loads out of that same machine may have been perfect---or not.
TYPICAL%2BLOAD%2BDATA%2BTEST%2BGUN.jpg
 
Chronos are cool and a great tool.
I would say just remember the vel shown is for your chrono on that day at that time. Different day, same ammo your chrono (or another one) might read a little different.

Walkalong showed how not to reset one here

http://www.thehighroad.org/showthread.php?t=733530
#19
Click to expand...

That WAS a ridiculously clean hole (you mentioned to Walkalong in the linked thread)..Never seen a whole that clean, Ive never shot a wadcutter but I guess that's the point. I thought it was a hole from the manufacturer, where a knob was supposed to go or something.
 
I had the same problem with the hole in Walkalong's photo....had to look twice. I do see the same holes with wadcutter's in paper; in a "Visicolor" or similar target, instead of the hole piercing the paper and tearing it like a ball round would do, the wadcutter just punches it out.
 
There are two kinds of people; those who have shot their chrono, and those who will.

RMD
 
I havent taken mine out of the box yet. I figure I'll let it enjoy its life for a little while longer-
 
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