Finding MV

Joined
Dec 14, 2018
Messages
604
I've gotten a load worked up and have data filled out in the MV temp table on my Sig Kilo 2400 for 81F -2947fps, 72F-2945fps, and 52F-2890fps. I averaged the three and got 2930fps for the (main) MV setting.

I've shot the load @ 750 and 1000 yds. 750 hit dead center. My first shot @ 1000 was about an inch from the bottom of a 20" plate and the next few shots were low, missing the plate completely. I'm assuming I need to put in the MV of which I sighted the gun in at? or is averaging these the correct way to get an accurate MV for a handload? I'm dumbfounded why the load was shooting so much lower at just 250 yds further after hitting dead center @ 750. Shooting a 300 wm, 215 bergers for reference.
 

cwj

FNG
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Jul 9, 2020
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10
How many shots per strand did you use to get your average? What kind of powder? That difference in mv between the three at the lowest of 52 seems a little off to me
 
OP
SneakyThunderCat
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Dec 14, 2018
Messages
604
How many shots per strand did you use to get your average? What kind of powder? That difference in mv between the three at the lowest of 52 seems a little off to me
Usually I do 4-5 shots. Powder is h1000

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greaseywater

Lil-Rokslider
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Sep 7, 2018
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122
Changing just the MV input, here are the results I got:

215 gr projectile, G7 BC of 0.354, zero wind,


MV (fps)Drop at 750 yrds (in)Drop at 1000 yrds (in)
2930121.1252.6
2890125.1260.9

If the velocity varies as much as your measurements, and you were on the lower end on the day you were shooting at 1000, there might have been 8 (or more) inches of extra drop at 1000 yards, which would put you at or below the bottom of the plate. Meanwhile at 750, only 4 inches of drop would put you closer to the center than to the edge.

What are the SD and ES of your velocity measurements?
 
OP
SneakyThunderCat
Joined
Dec 14, 2018
Messages
604
Changing just the MV input, here are the results I got:

215 gr projectile, G7 BC of 0.354, zero wind,


MV (fps)Drop at 750 yrds (in)Drop at 1000 yrds (in)
2930121.1252.6
2890125.1260.9

If the velocity varies as much as your measurements, and you were on the lower end on the day you were shooting at 1000, there might have been 8 (or more) inches of extra drop at 1000 yards, which would put you at or below the bottom of the plate. Meanwhile at 750, only 4 inches of drop would put you closer to the center than to the edge.

What are the SD and ES of your velocity measurements?
I'm not sure, I never figured it up truth be told. I'm fairly new to the reloading game so not completely sure how to do that. Do you think that 52 degree reading threw it off that much? or maybe my average FPS of the three? It was about 70-72 degrees the day I was shooting.
 

Salmon River Solutions

WKR
Rokslide Sponsor
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North Idaho
H 1000 should definitely not change that must based on temperature. My velocity on my 300 win mag with the 215 Berger's only changed about 20 fps between 85 degrees and 20 degrees.

That's why I like the Hodgdon Extreme powders.
 
OP
SneakyThunderCat
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Dec 14, 2018
Messages
604
H 1000 should definitely not change that must based on temperature. My velocity on my 300 win mag with the 215 Berger's only changed about 20 fps between 85 degrees and 20 degrees.

That's why I like the Hodgdon Extreme powders.
Thanks for the info, I'll be sure to redo it and see what I get for data!
 

Salmon River Solutions

WKR
Rokslide Sponsor
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FYI, I know my chrono will spit out way different numbers depending on whether or not it is in the shade or in the sun. I usually just use the chrono to get close, and then within my ballistic calculator I will make slight adjustments to the velocity until I'm on at my 200 yard zero, and all the 100 yard increments out to 800 yards. Then I know my ballistic curve is correct for drop.
 

greaseywater

Lil-Rokslider
Joined
Sep 7, 2018
Messages
122
I'm not sure, I never figured it up truth be told. I'm fairly new to the reloading game so not completely sure how to do that. Do you think that 52 degree reading threw it off that much? or maybe my average FPS of the three? It was about 70-72 degrees the day I was shooting.

I'm with @LivetohuntID, it isn't the temp difference. H1000 should not vary 60 fps over 20 degrees.

In your three average velocities, two are close together. One is 60 fps low. But the low value seems like it might match up better to your results. Was there a big spread in your 4 to 5 readings that you used to calculate the average for those 3 groups? If so, that could be the source of error. Maybe your "true"average is lower than 2930. Do you still have the individual readings?

What kind of chronograph are you using?
 
OP
SneakyThunderCat
Joined
Dec 14, 2018
Messages
604
I'm with @LivetohuntID, it isn't the temp difference. H1000 should not vary 60 fps over 20 degrees.

In your three average velocities, two are close together. One is 60 fps low. But the low value seems like it might match up better to your results. Was there a big spread in your 4 to 5 readings that you used to calculate the average for those 3 groups? If so, that could be the source of error. Maybe your "true"average is lower than 2930. Do you still have the individual readings?

What kind of chronograph are you using?
I'm using one of those cheap caldwell chronos.

I shot a five shot group tonight (79 degrees) and averaged 2885 fps on a buddies chrono that's a little more sophisticated. With some colder days coming up this week I'll definitely have to gather new MV data.

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OP
SneakyThunderCat
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Dec 14, 2018
Messages
604
Just to follow up on this thread. I retested MV on a better chrono and decided to ditch the MV temp table data. Entered 2885 fps as data into my rangefinder and shot today at 600 and 1000yds. 600 hit 2 inches high, 1000 hit twice. Cold bore shot was right on the money, second shot was 3 inches low from center. Good enough for the girls I go out with. Thanks again for the help!

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