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Brad is correct... in JBM you can set "Std. Atmosphere at Altitude" or " Pressure is Corrected".

Most interesting topic, gentlemen... thanks all.

Pictures, please?

Does not answer the question... it is not about shooter bias. A perfect optomechanical zero still does not take into account the muzzle flip due to harmonics. Same reason why different loads have a different POI.

Ilya, this mechanical alignment device cannot take into account action/barrel/load harmonics. How close do you normally get with the first shot at 100 m?

Check any good ballistic program, a bullet fired from a level barrel takes MORE time to drop compared to one that is simply dropped. This is due to the vertical component of its vastly larger drag. Also, a bullet does not leaves the barrel "slightly unstable" and then stabilize down range. The...

In their literature FNH stated that the A3G barrels were chrome lined...

FN makes their SPR with high grade steel CHF barrels, and they are even chromed... they claim durabiity of 2X or more compared to normal steel barrels. HK and Sako also make/had made super accurate and durable CHF barrels. Their accuracy is reportedly veeery good, but not quite super duper...

Great for erosion resistance and huge powder loads... The question is (at least for long range) how accurate can they be made?

The ammo issued inWWI and WWII to all british infrantry men using bolt action rifles and LMG was the Mk VII load (spitzer bullet, modest BC), NOT the the Mk VIII (BT bullet). The brit Mk VIII bullet has a similar BC to the 30-06 M1 load (172 gr spitzer boat tail bullet). In any case, the...

The groups (at short/mid ranges) depend on the quality of the bullets, not the basic design. In the past, the flat base bullets were considered "better" for short range accuracy because of the relatively ease of production. Nowadays, not so much since you can get match grade boat tails.

Probably the drag model does not fits the bullet very well... common with many designs. Check this: http://www.exteriorballistics.com/ebexplained/index.cfm http://www.exteriorballistics.com/ebexplained/5th/24.cfm Play with this: http://www.geoffrey-kolbe.com/drag.htm

You can download the book here: https://archive.org/details/RifleAccuracyFactsFullV1.0FirstFullScan Theis, please post the pages 196-197

If you guys have "Rifle Accuracy Facts" by H. R. Vaughn, take a look at "wind drift" from page 195 on.

Both things can be true at the same time... calculating secundary effects such as SD and vertical POI variations wiht a crosswind, as you well know, require measuring certain bullet parameters with extensive and expensive testing. Shooters could observe these effects at certain...

True, with a constant wind. But the angle of repose of the bullet changes with a changing wind... http://www.exteriorballistics.com/ebexplained/articles/article2.pdf "the horizontal and vertical drifts due to the yaw of repose cannot be calculated because the necessary a very expensive...

Come'on guys, it's just a friendly discussion... There are many ways to slice it. Perhaps some better than others, but precisely we're here to get/share knowledge about all these tech tid bits, and see at what range, and in what case caring about secondary effects pays dividends.

Correct... http://bulletin.accurateshooter.com/tag/aerodynamic-jump/ But since we are discussing SD, aerodynamic jump has basically the same problem: it does exists, but establishing exactly (not guessing) what angle of attack the bullet takes in flight is the core of the problem. The fact...

Does anybody use a vertical correction for horizontal wind? Is there a program that takes it into account, or like SD varies a lot depending on the bullet used, twist, etc.? Theoretically, there is an up/down component, but I never see people using it.

There is no doubt gyroscopic drift exists, due to yaw of repose. The only doubt is exactly how much (you have to KNOW, not estimate this value at several ranges), and then when is it worth it to account for it.