6.5shooter Posted January 31, 2011 Report Share Posted January 31, 2011 Hello folks. This may or maynot be much of an issue to some people who shoot lots of comps who know what their rifle is doing at all ranges due to regularly shooting them at known ranges. For the likes of me who depends on a range finder and ballistic program (exbal) i shoot at rabbits etc and steel targets at unknown ranges i depend on the actual bullet bc. From shooting my 123 scenat bullet i notice the bc must be slightly lower as out to 600 my load is 1-2 inch lower than given on exbal. I know this is not majorly significant but may mean a miss on a rabbit etc. Does anyone know of any actual bc data for this bullet in question or a list of bullets? I could fudge it a bit on exbal but would like to know the actual bc. Or how does everyone else in this situation calculate? Assuming temp and air pressure are all correct. Garry Link to comment Share on other sites More sharing options...
rabbit fingers Posted January 31, 2011 Report Share Posted January 31, 2011 'Applied Ballistics for Long Range Shooting' by bryan litz is probably your best bet, I don't have a copy yet, but found some data from it for the 140 amax and it is spot on. Link to comment Share on other sites More sharing options...
Davy Posted January 31, 2011 Report Share Posted January 31, 2011 Litz does not list the .264" 123 grain Scenar in the original version of Applied ballistics, hopefully it will be included in his new version along with some of the other missing links... I still have a theory that regardless of the given BC and velocity at different distances things change for skinny higher BC projectiles when hit hard, as an example push a .224" 80 grain SMK at 3500fps+ and it defies logic once it gets to 1000 yards and appears to shoot flatter. I was prepared to blame the 'scope but I have tested a couple of times and they just defy JBM tables and my calculations. Link to comment Share on other sites More sharing options...
brown dog Posted January 31, 2011 Report Share Posted January 31, 2011 From shooting my 123 scenat bullet i notice the bc must be slightly lower as out to 600 my load is 1-2 inch lower than given on exbal. If you're using G7, it gets optimistic as you get out to 6-700 and beyond [ http://ukvarminting.com/forums/index.php?showtopic=9715 ]. G1 is generally slightly worse. They're both only approximations; G7 is a better approximation to a pointy BT bullet than G1 below 6-700m. That's the theory. Now a bit of real-world: You need to be a little more realistic about tolerances: 1-2 inches out at 600; let's call it 1.5inches. And lets put that into rough MOA terms. You have a program that you believe is 0.25MOA out on elevation at 600 Bright to overcast light (or vice versa) will move you vertically double that; let alone unseen vertical wind components. If you think you're modelling within 0.25MOA vertically; you're 'ON' (What's your average group size at that distance?) Link to comment Share on other sites More sharing options...
6.5shooter Posted January 31, 2011 Author Report Share Posted January 31, 2011 If you're using G7, it gets optimistic as you get out to 6-700 and beyond [ http://ukvarminting.com/forums/index.php?showtopic=9715 ]. G1 is generally slightly worse. They're both only approximations; G7 is a better approximation to a pointy BT bullet than G1 below 6-700m. That's the theory. Now a bit of real-world: You need to be a little more realistic about tolerances 1-2 inches out at 600; let's call it 1.5inches. And lets put that into rough MOA terms You have a program that you believe is 0.25MOA out on elevation at 600 Bright to overcast light (or vice versa) will move you vertically double that; let alone unseen vertical wind components. If you think you're modelling within 0.25MOA vertically; you're 'ON' (What's your average group size at that distance?) Hi Brown dog. My average group size would be around 3 inch mark for 6-700 yards. This G7 bc figure, what ballistics program will run it and is it more accurate than g1? Its funny because my bc figure for 60 vmax in my swift is spot on but it just seems to be boattails that vary a little. Garry Link to comment Share on other sites More sharing options...
6.5shooter Posted January 31, 2011 Author Report Share Posted January 31, 2011 Where can i get my hands on applied ballistics? Is it just a book. Garry Link to comment Share on other sites More sharing options...
Davy Posted January 31, 2011 Report Share Posted January 31, 2011 Yes, just a book...more about it here: http://www.appliedballisticsllc.com/ Content wise it is a huge step forward from previous offerings and I have a copy within arms reach right now however it has all too soon been adopted as the bible and 'if Litz writes it then it must be true' which I am not sure it always is.... Very worth getting though. Link to comment Share on other sites More sharing options...
6.5shooter Posted January 31, 2011 Author Report Share Posted January 31, 2011 Thanks Davy. Does anyone know where i can get my habds on it in the uk along with his ballistics program? Or know of anyother G7 based ballistics program i can use? So does the bc increase with more velocity aswell? Just when you say that youre 80 smk flies flatter when driven hard the bc must be a variable? Is this the same for G7 figures? Garry Link to comment Share on other sites More sharing options...
Davy Posted January 31, 2011 Report Share Posted January 31, 2011 The ballistic app is free from the Berger site: http://www.bergerbul...gram/index.html The book, well mine came from Litz himself but I have a feeling he now sells through a distribution partner, details are on his site. G7's do change with velocity, choose another projectile and I will dig the numbers out for you! EDIT - JBM also supports G7 if you have the figure yourself. The Litz G7's used to be published on line but have been removed, equally BulletFlight used to show G7 in plain text but that has been removed with a later build, the only commercial source I can think of is the Litz book. The G7 for projectiles in theory should increase with velocity however this is not the case with some of the heavier projectiles and is a product of design. The SMK80 itself rises from.212 at 1500fps to .224 at 3000fps, of course you could argue that it was dropping in this case as bullets are invariably decelerating with time of flight. I have no data for 3000+fps but regardless of this it would be largely redundant as the part of the flight I am interested in is at 1000 yards onwards or the bit from 1600fps to the target at around 1400fps. Link to comment Share on other sites More sharing options...
6.5shooter Posted January 31, 2011 Author Report Share Posted January 31, 2011 So G7 is more reliable or is G1 reliable also with the accurate actual bc? Say a 155 scenar with G1 508 bc. At 2850 fps. I will compare it with exbal and see what it compares. Cheers Garry Link to comment Share on other sites More sharing options...
Davy Posted January 31, 2011 Report Share Posted January 31, 2011 I know that one off by heart! 155 Lap Scenar G7's: 1500 .230 2000 .232 2500 .240 3000 .244 I am slightly up on your velocity and expect around 887m/sec or 2910fps at 19C a 28Minute rail gives me a near perfect 100m zero (One Kick up) and 30MOA ish at 1000 yards, I work in 1/10 millrads with my 7,62x51 and it is 87 klicks according to my table. Link to comment Share on other sites More sharing options...
terryh Posted January 31, 2011 Report Share Posted January 31, 2011 Gents, Do not know if you know this but radar derived perfomance for Lapua bullets is avaialable free on the Lapua web site plus a ballistics program to use it. Basically if your miss either it's you or the data you put in See: http://www.lapua.com/en/customer-center/lapua-ballistics/download-lapua-edition.html Brgds Terry Link to comment Share on other sites More sharing options...
6.5shooter Posted February 1, 2011 Author Report Share Posted February 1, 2011 Thanks fellas, I think i will have to start altering my bc figures and see if i can get close to my real world testing. Maybe i will also trying to point my bullets and see if that brings me close to the actual advertised bc. Thanks Garry Link to comment Share on other sites More sharing options...
Lindy Posted February 8, 2011 Report Share Posted February 8, 2011 I've never had any unmodified ballistic program without modification predict my long-distance field results, and I have or have used a bunch of them. There are a variety of reasons why that happens. Here are some of those reasons, though the list is certainly not inclusive: Sources of Ballistic Program Inaccuracies Link to comment Share on other sites More sharing options...
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