Here is my problem - The BC of the 190 grain berger vld is stated at G1 .566 and G7 .290, If i use the application to true the BC it needs to move to G1 .810 and G7 .414.
This seem a massive change. Do you think the magneto speed velocity is on the slow side? To achieve the right curve by adjusting the MV it would need to shift to 3240fps which is 160fps faster. Could the chrono be that far out?
First off, the BC of the 190gn Berger is NOWHERE near 0.81/0.414, nor for that matter any other .30 calibre match bullet on the market. Those BCs take you into machined monometal 0.338 calibre custom match bullets - and there are only one of two of them achieving G7 BCs significantly above 0.4.
So, there is either something way wrong in your use of the ballistics program, or the base inputs, the main ones being MV and scope click value. The latter is the usual culprit. You rarely get 100% accurate correlations from an uncalibrated out of the box scope and I've seen tests of expensive scopes that were 10% 'out'. These days 3-5% error is more common, but a 100% accurate scope is a real rarity.
Bryan Litz goes into great detail on how this is done using a 'tall target' at a known and very accurately measured short distance, eg 100 yards. It's measured precisely muzzle to paper because your local 100 yard range may or may not see 100 yards between these two points and in fact is more likely on older facilities to not see them.
The rifle is zeroed to point of aim at whatever distance, MV accurately measured, and a tall target used. How tall depends on how far you're shooting and what the calculated come-up from the zero is. I don't work or think in milirads, rather MOA. A typical elevation rise from 100 to 600 for many cartridges will be around 10-MOA. 1-MOA = 1.046 inches per 100 yards, so 10-MOA (as an example) means that with a perfectly zeroed rifle, the group should print just under 10 1/2 inches above the POA at 100 yards (or 62.76 inches low at 600 yards on an unchanged 100 yard zero) when the scope has had that amount of elevation added to the turret. So, let's say that the group centre is 9 inches or 11.5 inches above the POA and that everything has been input absolutely accurately into the program. In those cases, the turrets click values are 1.5 over 10.5 x 100 over or under adjusting the actual elevation setting and a correction can them be built in. For Litz and his buddies in the ELR game shooting at various distances out to two miles, the calculated actual come-up at 100 yards is used on the 'tall target' and the actual scope turret change needed to get there recorded.
I said if everything has been input correctly into the program. That is actual scope height above the bore centreline, not the default 1.5". if your set-up is significantly different, calculated bullet drop will be wrong especially at modest distances such as out to 600 yards. Then there is altitude, ambient temperature and atmospheric pressure - modest effects at 600, very significant indeed at beyond 1,000. (There is a just over 1-MOA difference between 308 1,000 yard FTR settings for Diggle (~800 ft ASL) and Bisley (100? 200?) That's 10.46 inches difference in bullet strike. Double that between Bisley on a cold winter's day and Diggle in a hot summer's day (yes, the Pennines occasionally see them!).
You don't say what your load is or your barrel length. The MagnetoSpeed may be giving you bum data (check battery voltage - they apparently work when the battery gets low, but reliability goes to pieces). However, loads data and/or QuickLOAD will give a pretty good handle on whether your actual MV is higher or not.
Finally, small errors / changes can make 100-600 yard rise calculations way out, especially actual scope height. Another factor is group size. You are measuring from group centre to group centre. If single shots are used the rifle / load is only capable of 1-MOA groups then a 100 yard test can be 2-inches wrong if one is unlucky enough to have one at the low end and the other at the high. 2 inches is a big error at 100 yards. A frined who used to do a lot of scope testing for publication including the 'round the box' shots (one shot then +20-MOA - right 20-MOA, down 20-MOA, left 20-MOA should produce a true square with holes 20.9 inches apart and shot 5 touching shot 1) used a full-house 6PPC HV benchrest rifle capable of shooting groups on or under a tenth of an inch. Anything that produces say half-inch groups at 100 immediately risks producing a significant error through shot dispersion.
Is the scope correctly mounted? Any degree of cant affects both windage and elevation click accuracy, not that much at 600 yards, but it adds up.
At longer distances conditions on the day can have a major effect. Going back to Litz and his tall target calibrations, the ambient conditions are very carefully measured then settings are adjusted in the actual field / competition conditions - when you're talking about 1 to 2 miles distances a change in range altitude, a few degrees temperature difference, higher or lower atmospheric pressure can see you shoot many feet high or low at the target if not correctly accounted for.
