sporting rifles Posted October 24, 2011 Report Share Posted October 24, 2011 I have been having a debate with a mate about tragetory validation,to cut a long story short both out rifles have been chronoed on the same day and the 2nd time we got massive difference in velocity.ecen when I dropped my powder charge by 2gr it read over 100 FPS faster anyway I went to Bisley yesterday and on the 600 yards range I dialed in 7.50 MOA which my chart said,it took me 2 shots to hit the V bull as I needed 9 MOA when I got back home I validated the actual MOA used and the FPS came back as 3548 instead of 3876 which was the average after chronoing Saturday now Iam deabting with my mate the correct way to validate the actual drops,I say input the actual MOA used and hes sayd adjust the BC of the bullet as the chrono cant be that far out now for the experience users of this programme what is the right thing to do,I say input the MOA used at a set distance Link to comment Share on other sites More sharing options...
1967spud Posted October 24, 2011 Report Share Posted October 24, 2011 also just note that these stupid sunny days are really playing havoc with chronos at the moment , the other day i exsperienced over 200 fps difference on group that i was shooting that i know dam well isnt that far out other people who ive spoken to in the last week are havijng the same problems going back to your query you should always fudge the bc to make your real time drops to come right BUT and its a big but atmospherics will make a huge difference to fps and pressure and thus effect your drops exbal will get you there roughly in the first place, but you need to fill in all the relative data for that day i.e. temo air pressure etc to make it more exact and reliacble Link to comment Share on other sites More sharing options...
Ronin Posted October 24, 2011 Report Share Posted October 24, 2011 Mnufacturers claimed BC is rarely accurate - unless you look at Scenars and a few others which have been varified by dopler radar... When using Exbal (before relying on Matts cards) I used to ajust the BC to suit to drop at known distances. Link to comment Share on other sites More sharing options...
sporting rifles Posted October 24, 2011 Author Report Share Posted October 24, 2011 Mnufacturers claimed BC is rarely accurate - unless you look at Scenars and a few others which have been varified by dopler radar... When using Exbal (before relying on Matts cards) I used to ajust the BC to suit to drop at known distances. so even if the velocity was wrong you would still fudge the BC ?? Link to comment Share on other sites More sharing options...
6.5shooter Posted October 24, 2011 Report Share Posted October 24, 2011 I usually add 10 fps to the chrono reading to compensate the chrono being 10-15 feet from the muzzle. Does anyone else do this? Garry Link to comment Share on other sites More sharing options...
Gran Posted October 24, 2011 Report Share Posted October 24, 2011 The weather doesn't look too bright for tomorrow so I will check the chrono in the morning. Too much sun on the sensor might explain too high a reading but if it still says the same as last Saturday...... Gran Link to comment Share on other sites More sharing options...
Gran Posted October 25, 2011 Report Share Posted October 25, 2011 While we are on the subject which "G" profile should be used for 80grn target/varmint? Should it be "G2"/"G3" or something else? Still looks sunny here but I'll nip out anyway. Link to comment Share on other sites More sharing options...
Ronin Posted October 25, 2011 Report Share Posted October 25, 2011 so even if the velocity was wrong you would still fudge the BC ?? No, you need all the data to be accurate on the day of the test, velocity (average of all shots taken),temp, distance to zero, humidity, altitude, angle to target etc etc . Then if the hard data is correct and youre finding inconsistant results "downrange", ajust the BC to suit your down range findings. better still, on the day you check all data, place targets at known distances as far out as you can and measure the actual drop at each distance. Then you will be 100% sure of you drop data (for that temp, humidity and altitude on that day) You will get variations, for the above reason (temp, angle to target and humidity) Initial data must be spot on otherwise crap in, crap out.... Link to comment Share on other sites More sharing options...
1967spud Posted October 25, 2011 Report Share Posted October 25, 2011 While we are on the subject which "G" profile should be used for 80grn target/varmint? Should it be "G2"/"G3" or something else? Still looks sunny here but I'll nip out anyway. When you know the drag of th bullet at all velocities, you can determine which of the standard drag functions (g1 g7 g8) best suits your particular bullet. The G figure is relative to the type of bullet form facter. Link to comment Share on other sites More sharing options...
Gran Posted October 25, 2011 Report Share Posted October 25, 2011 When you know the drag of th bullet at all velocities, you can determine which of the standard drag functions (g1 g7 g8) best suits your particular bullet. The G figure is relative to the type of bullet form facter. & what information do you require to work that out for me my new best friend Keith p.s. might have found an issue...I have taken the chrono out to set it up prior to nipping out & the bases weren't clicked together quite flat, this would mean on a very small scale the sensors would not have been parallel & closer together.....could this cause higher readings? Link to comment Share on other sites More sharing options...
Gran Posted October 25, 2011 Report Share Posted October 25, 2011 It would appear that although it as been a long time since I was a schoolboy I haven't lost the ability to make the same errors Clicked the base down tight & shot 3 under a cloudy sky & got the expected readings from previous loadings. i.e. 3,200 fps avarage. So all we need to clear up now is which "G" profile to use and Bob's your Uncle. Keith. Link to comment Share on other sites More sharing options...
sporting rifles Posted October 25, 2011 Author Report Share Posted October 25, 2011 It would appear that although it as been a long time since I was a schoolboy I haven't lost the ability to make the same errors Clicked the base down tight & shot 3 under a cloudy sky & got the expected readings from previous loadings. i.e. 3,200 fps avarage. So all we need to clear up now is which "G" profile to use and Bob's your Uncle. Keith. thats the last time you set the chrono up no good you looking for the "G" spot your wife says you couldnt find hers Link to comment Share on other sites More sharing options...
1967spud Posted October 25, 2011 Report Share Posted October 25, 2011 what bullets are you using gran? Link to comment Share on other sites More sharing options...
sporting rifles Posted October 25, 2011 Author Report Share Posted October 25, 2011 what bullets are you using gran? 80gr berger varmints Link to comment Share on other sites More sharing options...
1967spud Posted October 25, 2011 Report Share Posted October 25, 2011 80gr berger varmints im presuming these are 6mm if so you use a g1 figure of .316 Link to comment Share on other sites More sharing options...
sporting rifles Posted October 25, 2011 Author Report Share Posted October 25, 2011 are you ? or do you know gran bob? what ????????????? Link to comment Share on other sites More sharing options...
Gran Posted October 25, 2011 Report Share Posted October 25, 2011 are you ? or do you know gran bob? We are both shooting 80grn flat base Varmints. pn 24321. manufacturers BC is .306 "G1" & .316 are these the correct settings? Gran Link to comment Share on other sites More sharing options...
Gran Posted October 25, 2011 Report Share Posted October 25, 2011 thats the last time you set the chrono up no good you looking for the "G" spot your wife says you couldnt find hers New wife is sapping my strength Pete keep having lapses of concentration..... Gran. p.s. I am a man...what's a g spot & is it on defra? :D Link to comment Share on other sites More sharing options...
1967spud Posted October 25, 2011 Report Share Posted October 25, 2011 We are both shooting 80grn flat base Varmints. pn 24321. manufacturers BC is .306 "G1" & .316 are these the correct settings? Gran sorry typo error should be as you said .306 Link to comment Share on other sites More sharing options...
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