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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
G7 > G1 ; resistance to BC change
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<blockquote data-quote="LouBoyd" data-source="post: 505658" data-attributes="member: 9253"><p>The reason there are multiple drag functions is that different projectile shapes don't loose their for forward velocity and energy at the same rate as a function of velocity. There is no one drag function which is a good fit for all projectiles. The "G" finctions we commonly use were established based on the shape of various artillary projectiles in the period between WW1 and WW2 a time when there were no electronic computers. Though they were deriived mostly for field artillary, they were usable for small arms as they scale fairly well, though not exactly. . They were a simplifcation which allow compuations to be made by "computors" which were rooms of people (usually women) trained to make manual computatations rapidly and with decent accuracy. Error correction was done by having the same computations done by multiple people and the results cross checked.</p><p> </p><p>Commercial bullet makers picked up the G1 model before WWII as it was a decent match for most bulets they sold and gave the largest humbers of the various G functions which helped sales. It has long been recgnized that higher numbers mean more delivered energy, flatter trajectory, and less wind deflection even for other ballistic functions predating the G functions, even though high BC don't necessarily mean better accuracy at short to moderate range. The G1 function served well up to the advent of personal computers in the 1980's. There were boattail bullets before that time but no laser rangefinders and few "VLD" bullets. </p><p></p><p>Even now the G1 BCs are good enough to not be a significant source of error for all but precision long range hunting and sniping. Long range target shooters don't care much about BCs since they can use sighter shots to get on fixed distance targets. Military snipers don't care much about BC's either. They have the exact drag funtions of the specific bullets they use for their ballistic lookup tables and ballistic computers. The US milatary abandoned using BCs in it's calculations long ago. See "Modern Exterioir Ballistics" by Rober F. McCoy of the Aberdeen MD Ballistic Research Lab. (BRL) Even it is getting out of date. It was Robert McCoy however who introduced BCs to the world of personal computers with his BASIC program McTraj on which most modern personal computer programs are based. He use BCs to make his program more useful to shooters who use commercial bullets. </p><p></p><p>Uncertainty of downrange wind velocity is still a larger souce of error than which G function is used for everything other than shooting at ranges with multiple wind flags or shooting in calm conditions. That will change in the future as better portable downrange wind sensors are devloped.</p></blockquote><p></p>
[QUOTE="LouBoyd, post: 505658, member: 9253"] The reason there are multiple drag functions is that different projectile shapes don't loose their for forward velocity and energy at the same rate as a function of velocity. There is no one drag function which is a good fit for all projectiles. The "G" finctions we commonly use were established based on the shape of various artillary projectiles in the period between WW1 and WW2 a time when there were no electronic computers. Though they were deriived mostly for field artillary, they were usable for small arms as they scale fairly well, though not exactly. . They were a simplifcation which allow compuations to be made by "computors" which were rooms of people (usually women) trained to make manual computatations rapidly and with decent accuracy. Error correction was done by having the same computations done by multiple people and the results cross checked. Commercial bullet makers picked up the G1 model before WWII as it was a decent match for most bulets they sold and gave the largest humbers of the various G functions which helped sales. It has long been recgnized that higher numbers mean more delivered energy, flatter trajectory, and less wind deflection even for other ballistic functions predating the G functions, even though high BC don't necessarily mean better accuracy at short to moderate range. The G1 function served well up to the advent of personal computers in the 1980's. There were boattail bullets before that time but no laser rangefinders and few "VLD" bullets. Even now the G1 BCs are good enough to not be a significant source of error for all but precision long range hunting and sniping. Long range target shooters don't care much about BCs since they can use sighter shots to get on fixed distance targets. Military snipers don't care much about BC's either. They have the exact drag funtions of the specific bullets they use for their ballistic lookup tables and ballistic computers. The US milatary abandoned using BCs in it's calculations long ago. See "Modern Exterioir Ballistics" by Rober F. McCoy of the Aberdeen MD Ballistic Research Lab. (BRL) Even it is getting out of date. It was Robert McCoy however who introduced BCs to the world of personal computers with his BASIC program McTraj on which most modern personal computer programs are based. He use BCs to make his program more useful to shooters who use commercial bullets. Uncertainty of downrange wind velocity is still a larger souce of error than which G function is used for everything other than shooting at ranges with multiple wind flags or shooting in calm conditions. That will change in the future as better portable downrange wind sensors are devloped. [/QUOTE]
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