Bad chronograph?

Tim

Tim

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How likely is a STD Deviation of 400 with Hornady ELD Match 140g 6.5CM?

Brand new, first 35 rounds were fired today, Savage FCP-SR 24" barrel.

Here were my numbers today...

2741
3008
3012
2694
2740
3766
2822
2847
2308
2305
2353
2462
2400

STD Dev 401.59

I'm thinking my chrono is not exactly accurate. No way that Hornady Match would be that bad. So, it's either the barrel or the chrono.
 
Something funky for sure.
Distance to chrono? Particulates can play hell.
Crazy lighting conditions?
My best guesses based on a little experience.
 
It's very important that the bullet travel through the sensor in the same spot each time.
If you are breaking your shooting position between shots, you are making changes.

Best thing is to put up a target 7 yds past the chrony, make a small dot to aim at.

You stay behind the rifle and someone else writes the numbers down.
Your shots should make one ragged hole at that distance.
Tighter the group, better the readings.
 
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MagnetoSpeed for rifle. No stupid stuff to shoot, no lighting conditions to have to worry about, and did I mention nothing to shoot?
 
Wow, an extreme spread of 707 fps? I am not sure you would get that variation between the minimum and maximum powder charges if you were reloading, and I am certain Hornady loads don't vary that much.

How far away from the muzzle was the chronograph? 10 ft is a good range to keep muzzle blast from affecting reading and to afford maximum opportunity to shoot the chronograph.
 
Charlie R said:
How far away from the muzzle was the chronograph? 10 ft is a good range to keep muzzle blast from affecting reading and to afford maximum opportunity to shoot the chronograph.
Click to expand...

Ye of little faith... I've staged the chrono at the 100 yard line to see what the velocities are at range. Got a couple of strange looks but I still have the same chrono....
 
Bailey Boat said:
Ye of little faith... I've staged the chrono at the 100 yard line to see what the velocities are at range. Got a couple of strange looks but I still have the same chrono....
Click to expand...

Bailey Boat, faith has little to do with it. I am merely speaking from my personal experience. Yes, I am embarrassed to admit it, but there it is.

I once read an article on another forum by a guy who used the user name, "Chronograph Assassin". My first thought was, "wow great handle, wish I had thought of it."

And more recently, I was at a match where the first shot through the chronograph (literally) pressed the backup unit into service.

Chronographs and I are kind of like my wife and house plants, after acquisition neither is long for this world. I guess that would make the magneto speed the "cactus" of chronographs.
 
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I agree - bad data. Tell us about the chronograph, how it was set up, conditions, etc. and how did those shots group?
 
Barrel break in. So I was cleaning, shooting 3-5 shot groups, then a quick clean and letting barrel cool between shots.

Mostly overcast day, some periods of bright sun.

It's a Shooting Chrony F1 ( https://www.midwayusa.com/product/531741/shooting-chrony-f1-chronograph) about 3 years old. Fresh battery. Set up ~10 foot from muzzle with the sun shades in place.

Shooting from a bench across a solid rest.

6.5 creedmoor, Hornady Match ammo.

Groups were all consistent at ~.85" per 10 shot target.
 
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Well your grouping size alone tells you that you are not experiencing those velocity differences, but something is definitely wrong with those velocity readings. Everything sounds good. I don't think that location within the sensor zone would make that big a difference. I am thinking that Bailey Boat may be right about something in/on the sensor that is interfering.
 
10 feet is way too close, especially for full power rifle. Pistol cals can sometimes get away with it.

I think the manual suggests triple that distance for rifles.

ETA- I checked my manual.
It wants 10 ft minimum for rifles, it suggests 15ft. It says "bigger the muzzle blast, further the distance."

I'd put it at 15ft and try again.
 
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The way my club's range is setup, a chrono on a tripod is a royal PIA. Waiting for a cold range to set up. Getting it level. Getting the height and light just right.....the magneto had a lot going for it
 
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