MV and vertical stringing

bpost

At what distance will variances in MV start to show up on target? There seems to be no noticable difference at 300 yards even with ES of over 50 FPS. Does it really matter under 1,000 yards?

shooter93

Depending on the cartridge, muzzle velocity and bullet weight you can see minor differences as close as 100 yards. With only 50 fps though the difference may very well be un noticeable. 100 or 150 fps can start to show though with a very accurate rifle. Typical varmit rounds will show the least because they are moving the fastest and are generally put in good shooting rifles. Big boomers that normally shoot in the 12 to 1500 fps range show discrepencies faster.

perry shooter

Hello I think there would be a number of factors but some of them would be the MV of the bullet to begain with as I think the faster a bullet starts out the shorter the flight time for gravity to act on the bullet would be . also the Ballistic Coefficient would have something to do with the outcome. but just one example at 500 yards is a 180 grain 308 diamenter bullet at 2700 FPS drop would be 48.5 " the same bullet at 2610 FPS would drop 51.5 inches.In 1000 yard shooting I would think reading the wind woul be more important to change the point of impact than the slight changes of muzzel velocity.

nononsense

bpost1958,

That's a complicated question to answer simply from the standpoint that there are a significant number of variables that can contribute to vertical or group dispersion on a target. We are about half of the problem while the other contributing factor is the lack of perfection in the environmental conditions during the testing.

If tested in absolute perfect ideal lab conditions where the muzzle velocity was the only variable, the variations in muzzle velocity should show up at your zero point. But bear in mind that we're talking about perfect shooting, no other variables at all including using a human to shoot. We can be fully 50% of the problems attributed to shooting errors. The other 50% is mechanical.

The drawback here of course is the lack of perfection of conditions, human mechanical and environmental. It doesn't exist. Therefore we have one heck of a time trying to discern what the exact cause of a variation is.

The other main problem is how we measure velocity and unfortunately this can depend on a money issue. Less expensive chronographs can show quite a large swing (inconsistancies) in reported velocities without changing any other variable. The better the chronograph, the fewer the errors. Operator error in setting up the chronograph can result in reporting variations. The lighting conditions will have an effect on the reporting also.

My suggestion is that if you can't discern a difference at 300 yards, the dispersal of the group is not letting you see the difference. There will be a noticeable difference at 1,000 yards.

Best.

ADDED:

This is one of those topics that sort of nags at the back of your mind while you're trying to get other things done. So here is another piece to add into the mix of this discussion.

Less or more velocity will result in less or more time for the bullet to be in the barrel. This will have a definite impact on the barrel time, harmonics of the barrel and then the point of muzzle departure of the bullet. This will show up as the bullet landing in a different spot on the target if all other variables are neutral.

Here's a list and discussion of some of the variables that can cause vertical in a shot string:

http://www.6mmbr.com/verticaltips.html

Best.