Have any of you tested enough with Nosler 165 grain Partitions or Accubonds to know whether Nosler's published values for ballistic coefficients for those two (0.41 for Partition and 0.475 for Accubond) are fairly close for .308/.30-06 velocities?

I believe each bullet manufacturer uses their own calculations to come up with the number.

I guess their pretty good when comparing bullets made by the same company, but may not be apples to apples when comparing bullets made by 2 different manufacturers.

Do they all use the same temp., altitude or barometric pressure in their formulas? I doubt it.

Some list the B.C. for high, medium, and low velocities. Some list the only one number, how they arrive at that is beyond me. Is it any average or the high? Maybe Mule Deer will know.

As far as testing different bullets B.C.'s, I'm not sure how that could be done. They are mathmatical formulas.

Best,

JM

if you have a chrono and use a good ballistic calculator you can figure the bc of the bullet by shooting at given distances. then putting the drop and other info into the calculator you can come up with the bc

Learn something everyday!

If that works that would be a fine way to compare bullets made by different manufacturers under identical conditions.

Thanks STX.

JM

JM i haven't done it myself but the guys that do a lot of longrange shooting use this method to find the actual bc of a bullet

If you want a realistic appraisal of BC's, buy Bryan Litz's book. It is the best thing ever published on the subject, and just came out last year. It includes a CD with one of the best ballistic programs as well.

thanks I'll have to get it.before we sold the ranch i was getting into longrange shooting with my 300rum (steel plates and hogs). got a place now that i can shoot out to 1000yds so when i get time I'll be setting up the steel

+1 on Bryan's book. I have a list of many of his suggested BCs in my documents. I have had several e-mail conversations with him and he is a great guy, very helpful and knowledgeable.

Recently I had a chance to visit a range with fixed steel targets at 300 meters, 385 meters and 500 meters. It is a silhoutte range. What a joy to paint the steel black and see the hits from the bench. I was able to shoot 6 different rifles at those targets. I can confirm that Bryan's BCs were very precise for quite a variety of bullets I use except one. I'll list the BCs of bullets I use down the page. I use the JBM program which includes MOA comeups which made using the turrets very easy.

The 200 gr accubond, 115 .257 Berger VLD, 125 nosler bt, 180 Berger 7mm VLD performed as predicted by Mr. Litz.

The one exception was the 150 nosler Ballistic tip. It's down range performance was what Nosler suggested .498. I actually used the G7 standard, I did some simple math and it is .254
The 150 nos bt worked with that G7 BC with a 7 rem mag and a 284 win. Both rifles are using moly coated bullets which might have caused the higher BC.

Mr. Litz uses chronographs not mathematical formulas to calculate BCs. He recommends using the G7 standard for boattails. read about it:

http://02b0516.netsolhost.com/blog1/?p=62



Not every program can utilize a G7 standard. JBM does:

http://www.jbmballistics.com/



Here is some data on barometric pressure and some BCs recommended by Mr. Litz.

Barometric pressure must be adjusted for the elevation with the JBM program:

Barometric pressure adjustments
2500ft 27.32
2550 27.07
3000 26.82
4000 25.84
5000 24.90
8000 22.23


Some BCs taken from Bryan's book or figured out with simple math:

257:
115 Berger VLD .466 (G1) .239 (G7)



.284:
168 Brg VLD .617 (G1) 316 (G7)
180 Brg VLD .659 (G1) 337 (G7)
175 SMK .310 (G7)
150 nosler bt .447 (G1) .229 (G7) or if Nosler BC is used .498(G1) .254(G7)

150 nosler E-tip .451(G1) .231 (G7)
162 A-max .599 (g1) .307 (G7)
160 Accubond .244 (G7)



.270:

130 nosler bt .427 (G1) .218 (G7)


.308:

165 sierra gameking .213 (G7)

165 nos bt .444 (G1) .227 (G7)

180 Accubond .481 (G1) .246 (G7)

200 Accubond .273 (G7) done mathematically by Bryan Litz



Hope this helps some. Get Mr. Litz's book for other BCs and lots more!!

Brain shoots the bullets over his equipment that he made. He uses wireless acustical targets spaced 600 yards apart. The farther apart the readings are, the more accurate the BC. Some makers use a computer model for thier BC's and others shoot them over 100 yard spacings. A few use 300 yards spacings and Brain is the only one that I am aware of that uses a 600 yard spacing. If Brain has tested the bullet that you are interested in, if you ask him he will tell you the numbers that he came up with.

Not to steal anything from posted information above, to add to the information I suggest for actual long range shooting, to toss out the computers and actually range test the loads you intend to shoot long range, and us the measured drop for future long shooting.....


I need to start shooting at longer ranges now that I found a local range to do my shooting at, to both verify drop and accuracy at longer ranges. No advantage to myy 257 and 300 Wby's if I don't know what the bullet is doing at 400 and 500 yds.

Any information on the 115 VLD's for deer / elk critters? I need to shop for bullets for the 257 Ultralightweight....


Allen

And then there are some factory-listed BC's that are just guesses--or "promotional."

A number of years ago a certain bullets company came out with a new boattail 7mm bullet with a listed BC (let's say) of .473. The next year a competing company came out with a boattail 7mm bullet of the same weight with a listed BC of .474.

When all is said & done, this is all that really matters; make your come-up chart from what your shooting says.

MM

No--but I've tested 270 150 gr PT's and BT's--and found them to be pretty much predictable according to Nosler's ballistic tables.

I trust Sierra's BC figures the most, Nosler a close second.

After that, my confidence on other brands BC's drop off quite a bit.



Casey

I shoot the 165 AB and BT from an '06 at 2940 fps. Lots of them.

Out to 600 yards the bullet tracks right with what my software says it should, as referenced by the come-ups of my scopes. It has tracked right with the adjustments of a vari-x III 2.5-8, and a 3-9 Conquest.

FWIW.

JB and/or MM,

So to calculate BC you don't need to measure drop, correct? You measure velocity at both ends of a known distance - longer the better?

Thanks,
Ron B

That's correct...

BC Calculator, velocity based

MM

Nice. Thanks!

kind of, but not really. the trick is to manipulate the computer program's inputs so the output matches the real, measured drops your rifle/ammo produces.

(unless you really plan on shooting at every 25 yard interval between 100 yards 1K under various conditions to get your dope)

IME have found that mostly if Exball isn't matching, then your imput data is off. Example, I chrono'ed my 338 Lapua and came up with 2820 FPS with the 300 SMK. My drop were looking okay out to 5-6 hundred yards. At 975 I was consistently low, so I started playing with the BC to match. I rechecked my zero and rechrono'ed the load. Tis time on an overcast day instead of the bright sunny day as before. This tim I came up with 2791 FPS. Now my program and my actual field data matched perfectly. I learned a lesson about very bright sunny days and chronographs. I was useing one of the best chrono'e made the Ohler 35

Yeah, a clear blue sky & a bright sun directly overhead can cause issues sometimes.

I have a PACT & on those kind of days, I use translucent shades over the skyscreens.........usually fixes the reliability problem.

MM

+1 on that...