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Author Topic: Chronograph question  (Read 910 times)

Offline SkookumHntr

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Chronograph question
« on: July 05, 2020, 04:31:15 PM »
Shot through a chronograph today, shooting my 300wsm, 165 grn Barnes tsx. The box says 3130 FPS at muzzle but I was getting anywhere from 3159 to 3189. Is it normal to be that much faster then what the box says? I need to send the info to leupold for my cds dial
 
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Online CP

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Re: Chronograph question
« Reply #1 on: July 05, 2020, 04:37:35 PM »
Less than 2% over.  That's in the noise.


Offline jasnt

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Re: Chronograph question
« Reply #2 on: July 05, 2020, 04:38:14 PM »
Every gun is different.  Box is just what they got with the test barrel
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338 lapua rc 239


The commission shall attempt to maximize the public recreational game fishing and hunting opportunities of all citizens, including juvenile, disabled, and senior citizens.
https://apps.leg.wa.gov/RCW/default.aspx?cite=77.04.012

Offline Bill W

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Re: Chronograph question
« Reply #3 on: July 05, 2020, 05:25:00 PM »
As stated above. Every gun is different.  Different lot numbers in all the components change things.

Offline jaymark6655

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Re: Chronograph question
« Reply #4 on: July 05, 2020, 05:52:09 PM »
I think a lot of precision or match ammo is allowed a 100 fps deviation across the lot. The printed data could be from several lots ago when the ammo was first developed and even though the powder may be the "same" it isn't the same powder anymore or a different batch. Also, who knows barrel length and bore dimensions used to first test ammo versus what your rifle is. Altitude and temp differences, ect.
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Offline Buckjunkie

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Re: Chronograph question
« Reply #5 on: July 05, 2020, 07:20:43 PM »
After many rifles and chronographed loads, it is what it is. I have fast rifles and I have slow. As some have said, the box shows speeds from a test barrel. If they had your barrel, they would be printing faster speeds on the box. It sells rifles and ammunition.

You are fortunate. Live with it.

Offline Magnum_Willys

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Re: Chronograph question
« Reply #6 on: July 05, 2020, 08:06:31 PM »
I wouldn't be surprised to see a 50 fps variation within a single box of factory ammo.   Sounds like you got some good ones.

Offline Stein

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Re: Chronograph question
« Reply #7 on: July 05, 2020, 08:07:00 PM »
What chrono?  Most are not calibrated or accurate.  You can plug the speed and be in and shoot it out long distance and verify.


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Offline MtnMuley

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Re: Chronograph question
« Reply #8 on: July 05, 2020, 09:48:55 PM »
My bet is the Chrony you're using and if it's even calibrated correctly.

Rest assured though.......they're stupid rutting bucks in November and you'll get a follow up shot or two :chuckle:

Offline Bill W

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Re: Chronograph question
« Reply #9 on: July 06, 2020, 08:10:40 AM »
My bet is the Chrony you're using and if it's even calibrated correctly.

Rest assured though.......they're stupid rutting bucks in November and you'll get a follow up shot or two :chuckle:

If there's a defined spot for the front sensor and a defined spot for the back sensor all the machine has to do is measure the time of flight and convert it to fps.  It's pre-set.  Chronie has to have the sensors in line with the muzzle and the target.  Any bit of angle changes the defined measurement to something slightly shorter.

Online Mtnwalker

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Re: Chronograph question
« Reply #10 on: July 06, 2020, 08:22:53 AM »
Youíre basically averaging 45 fps faster than what the box says, which isnít much. My guess is your chrono is just fine And itís just rifle to rifle variation. Also it doesnít surprise me with Barnes, I donít think they fluff their data as hard as some other companies. My 338 also shoots faster than what the box says with their ammo.

Offline b23

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Re: Chronograph question
« Reply #11 on: July 06, 2020, 09:17:34 AM »
Maybe it's gotten better over the years, I don't shoot much factory ammo so can't say, but it's been my experience with chronographing factory ammo that it tends to be all over the map and the stuff I've run across a chronograph is usually slower, sometimes a lot slower, than what is printed on the box.  I had some 338-378 ammo from Nosler that was over 200 fps slower than what they claimed but Nosler tends to embellish their numbers a fair amount too.

I think if you're consistently within 50fps of what the box claims and you aren't getting extreme ES numbers, for factory ammo, that's probably pretty good.

Offline jasnt

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Re: Chronograph question
« Reply #12 on: July 06, 2020, 05:50:04 PM »
Maybe it's gotten better over the years, I don't shoot much factory ammo so can't say, but it's been my experience with chronographing factory ammo that it tends to be all over the map and the stuff I've run across a chronograph is usually slower, sometimes a lot slower, than what is printed on the box.  I had some 338-378 ammo from Nosler that was over 200 fps slower than what they claimed but Nosler tends to embellish their numbers a fair amount too.

I think if you're consistently within 50fps of what the box claims and you aren't getting extreme ES numbers, for factory ammo, that's probably pretty good.
:yeah:
243Round ct. 158
338 lapua rc 239


The commission shall attempt to maximize the public recreational game fishing and hunting opportunities of all citizens, including juvenile, disabled, and senior citizens.
https://apps.leg.wa.gov/RCW/default.aspx?cite=77.04.012

Offline CaNINE

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Re: Chronograph question
« Reply #13 on: July 06, 2020, 06:01:51 PM »
...and hopefully the next box of ammo you buy will be in the same ballpark. You may want to stock up on all the sale lot number if possible. Especially if you are going to set a CDS to factory ammo. Something to consider.
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Offline jasnt

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Re: Chronograph question
« Reply #14 on: July 06, 2020, 07:14:18 PM »
If this was a light activated chrono it could off any way.  Most are +/- 2% so possibly +/- 60 FPS around 3000fps if you where lined up square with bullet path
243Round ct. 158
338 lapua rc 239


The commission shall attempt to maximize the public recreational game fishing and hunting opportunities of all citizens, including juvenile, disabled, and senior citizens.
https://apps.leg.wa.gov/RCW/default.aspx?cite=77.04.012

 


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