wind drift comparison question?

[AusFclass]

there are so many good cals out there but id like to know some FACTS about some cals that are close but which one is the best. i don't load for these so i cant give velocities to directly compare.
6-6.5x47 with 115
6.5x47 with berger 130
6.5x284 with 142SMK
7 08 with 168 or 180
284 with 180 berger
what drift would they have at 1000yd

 

[Cheechako]

aus

That's an impossible question to answer. The wind deflection,drift is something else) is a function of the BC and velocity of the bullet. Two bullets with the same BC, at identical velocities, will be deflected an equal amount regardless of the caliber or weight.

Ray

 

[SlowpokeRodriguez]

Velocity will be the key here along with the corresponding BC's. Try and imagine if you will time in flight as well--all things being equal which they seldom are the highest velocity will drift less.

 

[Henryp]

The .284 with 180 Bergers is the winner.The 6X47 with 108 Bergers at 3050 drift about 64", 6.5X284 142 Sierras at 2850 68", 284 at 3000,R-17) 51".

 

[Cheechako]

I think you'll have a fun time trying to get the 180 Berger to 3000 in a 284W case.

Having shot all of those bullets at long range I think you'd be a little better served using VLDs, if wind is your problem.

And once more for the record, it's wind deflection, not drift. At 1000 yards you'll probably need to add or subtract a MOA to compensate for drift.

JMHO

Ray

 

[AusFclass]

sorrry it should be wind deflection. we need to compare apples with apples ie 139 0r 142gr 6.5 VLD's against 180gr .284 not a 6.5 only using 108gr's. i think the 6.5x284 would be very close to the straight .284 but how much behind would a 6.5x47 really be? isn't this the question we all ask ourselves when trying to choose a new caliber? i don't want this question to get out of control!!

 

[Cheechako]

aus

No need for it to get out of control. You simply need to compare the BC of the different bullets at the real velocity they can be shot. Caliber or weight do not matter. It only takes a few minutes to run the numbers through an exterior ballistics program to see which one is favored.

I believe that the 180 Berger VLD has the highest BC of all that you mentioned but if you can only shoot it at 2700 fps it could be outclassed by lesser BC bullets. At 3000 it would be hard to beat but it would take a big case to do that. A 244 Ackley shooting the Berger 105 VLD at 3200 would probably beat it.

See what I mean?

And then you need to consider accuracy. Also, from your moniker I take it that you are an F Class shooter? The 180 may be more recoil than you can tolerate shooting prone.

Ray

 

[Raptor]

I agree with Cheechako. The other thing you need to remember is what looks good on paper does not always come true in the "Real" world with real wind.

The heavier bullets will just flat shoot tigher at l000yds than the lighter ones if the wind is blowing. This has proven true time after time for me.

I have a 260 shooting 123s and a 6XC shooting the 105s or 107s. My dials are identical for both rifles and the 123s will normally group better at 1000yds when the wind is blowing. My 6.5x284 shooting the 140AMAX and the 142s would do just a tad better yet. All of these guns would shoot the same at 600yds give or take but when you start getting out to 1000yds the heavy bullet shine. I would expect the 7MMs to be a tad better yet.

Real world shooting in the wind I will always go with a heaver bullet. This has proven out to many times for me.

 

[JHardy]

In my experience shooting 1000 yd prone next to others using various calibers from 6mm to 300 Win. Mag., my 284 Shehane,2950 fps)will shoot inside of them all -- easily. In fact, Charles Ballard,F-Class Open record holder and 2008 F-Class Open National Champion) has run tests with his straight 284 and 180 Bergers and it shoots inside of everything else you have mentioned at 1000 yards.

At 600, the advantage of the 7mm is still there if you miss a wind call, but the shorter distance,600 is NRA Mid-Range) will not bite you nearly as bad as a missed read at 1000.

With an adjusted BC by Bryan Litz, the 180 Berger still sports a .659 BC without closed meplats. At one time, the 7mm looked good on paper but there were no match grade bullets available. Not so now. Still, there has to be a balance between BC and match grade accuracy, and the 7mm gives you that.

Having said all this, there is nothing as fun to shoot at 600 than one of the 6mm chamberings based on the BR case. They will absolutely hammer with Rl-15,which gives accuracy and higher fps than Varget.)

Just my $.02,
Jim Hardy

 

[Raptor]

Jim,
I think you an I are saying the samething. Heavier bullets rule at 1000yds. Like you, if I am shooting 600yds only, I will take a 6MM in a heartbeat but not at 1000yds no matter how good the 115s look on paper they will not hang with the 142s or the 7mms at 1000yds in the wind. Maybe on a calm day but not from my experience with shooting on windy days.

 

[AusFclass]

ok thats good but what about the comparison of those cals shooting those projectiles at prouven velocities?