Real life performance 139gr Scenar vs 140 Berger VLD?

[6brbb]

Hi all,
I'm a New Zealand F-Class shooter new to this site.

For a number of years I have shot F-Class with a 6.5-284 with 139gr Scenars. I have had excellent performace with this bullet; and have taken out a number of competitions with it. I am however going to give the Berger 140gr VLD a try. I figure the extra BC is worth the effort.

Am interesting if others have compared the two and the change is recommended? Estimated reduction is elevation MOA at 1000 yards? Percieved reduction in windage required (though this is difficult to compare sometimes)?

I will post my 1000 yard test results as they come to hand.

Thanks all.

Glen

 

[savageboy]

My Shilen 1:8 twist wouldn't shoot the Bergers no matter what I tried- Jumping/ Jamming. I wanted the extra BC too. I have settled on the Lapua's. They work great and are a winning combination w/ H4831SC in my 260AI

 

[jr600yd]

Glen,
I've been shooting a 6.5/06 for years with both 142SMK's and 140VLD Bergers. I've found the Bergers shoot about 3-4 MOA lower than the Sierra's with the same load.

 

[Laurie]

Glen,

if you want to really find out about ballistics in long-range shooting, you need Bryan Litz's book:

Applied Ballisticsfor Long Range Shooting


http://www.appliedballisticsllc.com/index_files/Book.htm

As well as properly explaining what external ballistics mean for target shooters and how to use the knowledge in a practical way, Bryan includes experimentally derived data for 175 different bullets, mostly match types, obtained in actual shooting over 1,000yd and a 3,000 to around 1,500 fps velocity in flight range.

He is now Berger Bullets' Ballistician, but did the work and wrote the book before joining this company.

He doesn't like the commonly used G1 bullet model based drag curve based BCs as they vary too much according to velocity, and uses the G7 model instead that starts with a projectile form that is very close to a modern HPBTM shape bullet.

The book also includes a simple PC ballistics program to use with i7 (G7 based form factors) that he provides for the bullets and which are as I said based on actual range results at long ranges, not computer-based design calculations or short-range high-velocity results which is what manufacturers (other than Berger which now uses Litz data for all its match bullets) provide.

The key metric for any target shooter for a bullet is wind deflection (and in some disciplines like F-TR and TR/Fullbore Rifle, terminal velocity because of the transsonic zone / dropping into subsonic velocities issue).

Taking your two bulllets, (+ adding the 142gn Sierra MK which is very widely used in the USA), assuming 3,000 fps MV from a 6.5-284, it look like this for 1,000yd under standard environmental conditions for the trio:


Bullet i7 Value G1 BC G7 BC V1,000 D1,000

139 Lap Scenar 1.002 0.557 0.285 1,538 fps 70"

130 Berger VLD 0.918 0.612 0.313 1,644 fps 63"

142gn Sierra MK 0.968 0.588 0.301 1,605 fps 65"


i7 is in relation to the standard G7 projectile, 1.000 being identical, smaller than 1 producing less drag, greater than 1 more.

D1,000 is wind deflection in inches in a 10mph 90-degrees crosswind.

Incidentally using a 100yd zero, Bryan Litz's ballistic program says the 139gn Lapua would drop 272" at 1,000 compared to 263" for the Berger VLD, therefore requires just under 1-MOA extra elevation increase.

Hope this helps.

Laurie

 

[6brbb]

Thanks Laurie.
I agree Brian's book is amazing. I though I knew a lot until I read his book. Certainly a lot more educated now.

My calculations are close to yours. My calcs show a 1.3 MOA reduction is elevation for 1000yds (from a 100 yrd zero); and a 0.75 MOA reduction in windage (10 mph cross wind). Brian says in his book to go for the higher BC projectile; so thats what I am trying. The big benefit here is the 12% reduction in windage adjustment. If the 140VLD's can achieve the same velocity and can group like the 139gr scenars then I should have an advantage.

I have now loaded up a few test cases. With the 140VLD's just touching the rifling (according to Quickload) I achieve a similar usable case capacity to the 139 g Scenars. It's also sort of neat to see the loaded rounds COAL is a little longer.

Will try and do a 1000yd test on Saturday during a club F-Class shoot .... but we also have a very wet day forcast .... so will have to see. Am keen to see if the theory matches real life!

Thanks again.
Glen

 

[Laurie]

Will try and do a 1000yd test on Saturday during a club F-Class shoot .... but we also have a very wet day forcast .... so will have to see. Am keen to see if the theory matches real life!

Great stuff Glen - come back and say how it went.

In the UK, most people used the 139 Scenar when 6.5-284 was THE F-Open cartridge. Today, the top boys are mostly using 7mmWSM variations, although with a growing number moving to .284 Winchester because of the barrel life issue. Too rich for a poor F/TR shooter like me!

6.5-284 is doing very well here though in 600 and 1,000yd BR in the 'Factory Sporter' class, several people using the Savage 12 F-Class rifle and nearly unbeatable in class.



Best wishes,
Laurie

 

[daj]

I agree. Applied Ballistics for Long Range Shooting by Bryan Litz is essential reading for serious long range shooters. It is also a valuable cross-reference text for popular long range bullets.


Regarding the 139gr Scenar and 140gr Berger VLD:

In my limited field testing to over 1,000yds, I found the 140 Berger VLD performed as predicted by JBM software when using Bryan's BC data (G7=0.313), muzzle velocity and atmospheric data. No surprises there.

However, the 139 Scenars performed significantly better than predicted.

Long story short from Bryan. His test batch of 139 Scenars had a larger than normal meplat of 0.076". My batch measured 0.065".

I'm not sure if this meplat difference accounts for all the observed performance difference, but my 139 Scenars fly to a G7=0.296 compared to Bryan's G7=0.285.

Check your dimensions and tweak accordingly.

As far as performance in my 260Rem, when I hold my tongue just right the Scenars will clean the 4" centre at 600yd. However, since switching to 140 Berger VLDs, my score averages have gone up. The VLD definitely shoots better for me. Both are jammed 15T.