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CoffeedrinkerinNC
XCorporal
Rating: 3.1/5 this site
68 posts this site
Number of Rounds to Determine MV
12/07/2016
How many rounds over a chrono to get a good average for muzzle velocity? I remember from stats class the more the better. I worked up load for my 308 using OCW method, found the charge weight I want to use. Loaded up 50 more rounds and will be heading to the range this weekend to shoot 5, five shot groups at 100 yards. If the 100 yard groups are good, I plan to take the remaining 25 round out to 200 yards for 5, five shot groups.
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padom
XFirst Sergeant
Rating: 3.8/5 this site
3050 posts this site
Re: Number of Rounds to Determine MV
12/07/2016
I typically shoot 20 over the Magnetospeed once I finalized a new load to determine velocity.
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morganlamprechtXFirst Sergeant
Rating: 3.8/5 this site
1312 posts this site
Re: Number of Rounds to Determine MV
12/07/2016 Last edited 12/07/2016 by morganlamprecht
wasting a bunch of ammo/time...if they shoot ragged hole at 100, chrono 10 of them...if ES is less than 20-25 (if your reloading steps are done right this should be no problem) you should have no trouble on moa sized targets within the super sonic zone of your bullet
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padom
XFirst Sergeant
Rating: 3.8/5 this site
3050 posts this site
Re: Number of Rounds to Determine MV
12/07/2016
Ragged holes at 100 arent the say all be all unless thats all you do is shoot ragged holes at 100. Testing them at distance after finding your optimal charge weight and optimal seating depth is the only real way to know how your load performs. 500yd is the minimum I test after finding a new load and single digital SD's are the goal.
Rate now:
morganlamprechtXFirst Sergeant
Rating: 3.8/5 this site
1312 posts this site
Re: Number of Rounds to Determine MV
12/07/2016 Last edited 12/07/2016 by morganlamprecht
my results say otherwise
we have ways today to measure bullet velocity accurately and physics is physics...bullet manufacturing tolerances which cause any disparity down range is out of the reloaders hands, and with todays match bullets isnt much of an issue anyways
im all ears though if someone can explain to me how 2 (properly stabilized) bullets passing thru point A at the same speed, will not impact the same point B, given their manufacturing was the exact same
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BRU15XSergeant
Rating: 3.1/5 this site
167 posts this site
Re: Number of Rounds to Determine MV
12/07/2016 Last edited 12/07/2016 by BRU15
This is one of the big reasons I chose to buy a LabRadar, I chronograph every shot that I take so by the end of a range trip I can have upwards of 50-60 shots in a set.
Personally I think you can get away with just a few shots for an average but if you really want the most accurate data possible then you should chrono as many shots as you can.
Rate now:
jkonzalXGunny Sergeant
Rating: 3.3/5 this site
507 posts this site
Re: Number of Rounds to Determine MV
12/07/2016
To me, the chrono just gives you a start number to put in your balistics calculator. You can get that number with 5 shots, if they aren't all over the board. After you have that number, shoot on a paper target at 1k yards and make scope adjustments to bring your impacts to the center elevation of target. At that point, start adjusting the MV in your calculator until it matches the elevation turret on your scope. This will give you the best MV number.
Rate now:
pell1203XGunny Sergeant
Rating: 3.0/5 this site
561 posts this site
Re: Number of Rounds to Determine MV
12/08/2016
At some point if you are shooting at longer distances (>500 yards) it would be a good idea to shoot a tall target test to confirm your scope elevation clicks are working per specification.
Many turrets, while repeatable, require a minor correction factor to ensure the actual elevation offset matches the dialed elevation. The data collected from shooting the tall target test will allow you to compute the correction factor to apply when performing your long distance calculations. Many ballistic programs use this correction to tailor the solution to your specific rifle/scope combination.
Rate now:
TripleBullX8 MONTHS
Premium Member
Sergeant
Rating: 3.4/5 this site
257 posts this site
Re: Number of Rounds to Determine MV
12/08/2016 Last edited 12/08/2016 by TripleBull
--------
BRU15 wrote:
Personally I think you can get away with just a few shots for an average but if you really want the most accurate data possible then you should chrono as many shots as you can.
------------
Agreed, because if you are documenting the temperature, barometric pressure, etc., you learn about predicting ballistics across a range of conditions.
Rate now:
scudzuki
XFirst Sergeant
Rating: 3.4/5 this site
2600 posts this site
Re: Number of Rounds to Determine MV
12/08/2016 Last edited 12/08/2016 by scudzuki
Get in the ballpark with a chrono (I have a LabRadar), record actual drops @ known distances as far out as I can go, then tweak the MV in a ballistics calculator until observed drops (the "PE" in "DOPE") matches the output of the ballistic calculator. I have JBM online and Strelok Pro in agreement within .1 mil out as far as I can shoot here (200-700 yards) for my rifles. I also have Shooter on my Android but I've been unable get it to calculate external ballistics that match my DOPE.
XCorporal
Rating: 3.1/5 this site
68 posts this site
Number of Rounds to Determine MV
12/07/2016
How many rounds over a chrono to get a good average for muzzle velocity? I remember from stats class the more the better. I worked up load for my 308 using OCW method, found the charge weight I want to use. Loaded up 50 more rounds and will be heading to the range this weekend to shoot 5, five shot groups at 100 yards. If the 100 yard groups are good, I plan to take the remaining 25 round out to 200 yards for 5, five shot groups.
Rate now:
padom
XFirst Sergeant
Rating: 3.8/5 this site
3050 posts this site
Re: Number of Rounds to Determine MV
12/07/2016
I typically shoot 20 over the Magnetospeed once I finalized a new load to determine velocity.
Rate now:
morganlamprechtXFirst Sergeant
Rating: 3.8/5 this site
1312 posts this site
Re: Number of Rounds to Determine MV
12/07/2016 Last edited 12/07/2016 by morganlamprecht
wasting a bunch of ammo/time...if they shoot ragged hole at 100, chrono 10 of them...if ES is less than 20-25 (if your reloading steps are done right this should be no problem) you should have no trouble on moa sized targets within the super sonic zone of your bullet
Rate now:
padom
XFirst Sergeant
Rating: 3.8/5 this site
3050 posts this site
Re: Number of Rounds to Determine MV
12/07/2016
Ragged holes at 100 arent the say all be all unless thats all you do is shoot ragged holes at 100. Testing them at distance after finding your optimal charge weight and optimal seating depth is the only real way to know how your load performs. 500yd is the minimum I test after finding a new load and single digital SD's are the goal.
Rate now:
morganlamprechtXFirst Sergeant
Rating: 3.8/5 this site
1312 posts this site
Re: Number of Rounds to Determine MV
12/07/2016 Last edited 12/07/2016 by morganlamprecht
my results say otherwise
we have ways today to measure bullet velocity accurately and physics is physics...bullet manufacturing tolerances which cause any disparity down range is out of the reloaders hands, and with todays match bullets isnt much of an issue anyways
im all ears though if someone can explain to me how 2 (properly stabilized) bullets passing thru point A at the same speed, will not impact the same point B, given their manufacturing was the exact same
Rate now:
BRU15XSergeant
Rating: 3.1/5 this site
167 posts this site
Re: Number of Rounds to Determine MV
12/07/2016 Last edited 12/07/2016 by BRU15
This is one of the big reasons I chose to buy a LabRadar, I chronograph every shot that I take so by the end of a range trip I can have upwards of 50-60 shots in a set.
Personally I think you can get away with just a few shots for an average but if you really want the most accurate data possible then you should chrono as many shots as you can.
Rate now:
jkonzalXGunny Sergeant
Rating: 3.3/5 this site
507 posts this site
Re: Number of Rounds to Determine MV
12/07/2016
To me, the chrono just gives you a start number to put in your balistics calculator. You can get that number with 5 shots, if they aren't all over the board. After you have that number, shoot on a paper target at 1k yards and make scope adjustments to bring your impacts to the center elevation of target. At that point, start adjusting the MV in your calculator until it matches the elevation turret on your scope. This will give you the best MV number.
Rate now:
pell1203XGunny Sergeant
Rating: 3.0/5 this site
561 posts this site
Re: Number of Rounds to Determine MV
12/08/2016
At some point if you are shooting at longer distances (>500 yards) it would be a good idea to shoot a tall target test to confirm your scope elevation clicks are working per specification.
Many turrets, while repeatable, require a minor correction factor to ensure the actual elevation offset matches the dialed elevation. The data collected from shooting the tall target test will allow you to compute the correction factor to apply when performing your long distance calculations. Many ballistic programs use this correction to tailor the solution to your specific rifle/scope combination.
Rate now:
TripleBullX8 MONTHS
Premium Member
Sergeant
Rating: 3.4/5 this site
257 posts this site
Re: Number of Rounds to Determine MV
12/08/2016 Last edited 12/08/2016 by TripleBull
jkonzal wrote:
To me, the chrono just gives you a start number to put in your balistics calculator. You can get that number with 5 shots, if they aren't all over the board. After you have that number, shoot on a paper target at 1k yards and make scope adjustments to bring your impacts to the center elevation of target. At that point, start adjusting the MV in your calculator until it matches the elevation turret on your scope. This will give you the best MV number.
I think your approach is a starting point at estimating a calculator-based adjustment to a measured MV. The Litz "Applied Ballistics for Long Range Shooting" book recommends starting with an MV adjustment, then moving on to a ballistic coefficient adjustment. Etc. With respect to how many shots are needed to be chrono'ed, 10 is fairly standard but to a statistician, more is always better. Unless I'm hunting, I'm pretty much always chrono'ing with the LR.To me, the chrono just gives you a start number to put in your balistics calculator. You can get that number with 5 shots, if they aren't all over the board. After you have that number, shoot on a paper target at 1k yards and make scope adjustments to bring your impacts to the center elevation of target. At that point, start adjusting the MV in your calculator until it matches the elevation turret on your scope. This will give you the best MV number.
--------
BRU15 wrote:
Personally I think you can get away with just a few shots for an average but if you really want the most accurate data possible then you should chrono as many shots as you can.
------------
Agreed, because if you are documenting the temperature, barometric pressure, etc., you learn about predicting ballistics across a range of conditions.
Rate now:
scudzuki
XFirst Sergeant
Rating: 3.4/5 this site
2600 posts this site
Re: Number of Rounds to Determine MV
12/08/2016 Last edited 12/08/2016 by scudzuki
jkonzal wrote:
To me, the chrono just gives you a start number to put in your balistics calculator. You can get that number with 5 shots, if they aren't all over the board. After you have that number, shoot on a paper target at 1k yards and make scope adjustments to bring your impacts to the center elevation of target. At that point, start adjusting the MV in your calculator until it matches the elevation turret on your scope. This will give you the best MV number.
This mirrors my experience.To me, the chrono just gives you a start number to put in your balistics calculator. You can get that number with 5 shots, if they aren't all over the board. After you have that number, shoot on a paper target at 1k yards and make scope adjustments to bring your impacts to the center elevation of target. At that point, start adjusting the MV in your calculator until it matches the elevation turret on your scope. This will give you the best MV number.
Get in the ballpark with a chrono (I have a LabRadar), record actual drops @ known distances as far out as I can go, then tweak the MV in a ballistics calculator until observed drops (the "PE" in "DOPE") matches the output of the ballistic calculator. I have JBM online and Strelok Pro in agreement within .1 mil out as far as I can shoot here (200-700 yards) for my rifles. I also have Shooter on my Android but I've been unable get it to calculate external ballistics that match my DOPE.
