Home Forums Hunting & Shooting Ask The Gunwriters Question on BC for Mule Deer and Co.

I just got some Nosler 250 E-Tips to try out in my 9.3x62. They are of course longer than the 250 AB. Nosler list the identical BC (G1 .494) and SD (.267) for them both. The SD should be the same based on its formula but I am surprised at identical BCs. Makes me think maybe Nosler hasn't fully tested it. We all recall how optimistic many of their published BC used to be before independent labs started testing them. Any thoughts on this?
I am probably confusing longer bullets needing more twist with longer bullets having higher BC (all else being equal). Ogives look about the same, but the AB may have a little more pronounced boattail. And of course the E-Tip is a lot longer.

Thanks for your schooling,
Rex

Ballistic coefficient is dependent on both volumetric density and length.

Thanks Jordan. Does that mean that if the ogive, boattail and weight are the same, you would expect the longer bullet to have a higher BC?

Yes. But the length and angle of the boat tail can make a difference.


Okie John

It’s not quite that simple. The third variable in the calculation of BC is drag coefficient, which also depends on density.

Simplistically, you could say that, assuming equal drag coefficients (not necessarily the same shape), if the length increase of the mono over the C&C exceeds the reduction in density, the mono bullet would have a higher BC.

Thanks again for the replies.
I did something I should have from the start, which was to flip through the Nosler manual and compare the listed BCs for a variety of E-Tip and BT bullets of the same caliber and weight. In every case, the E-Tip was listed with a higher BC, sometimes significantly so and sometimes not so much, but always higher**.
Makes me think it's either just an error in the manual on the two 9.3mm 250s, or they hadn't gotten around to testing it yet and just used the AB's BC.

Cheers,
Rex

** Examples
6.5mm 120 E-Tip .497, 6.5mm 120 BT .458 (pretty significant)
7mm 140 E-tip .489, 7mm 140 BT .485 (noise level)
Visually, the differences between the pairs look about the same. Will study on it some more.

i sincerely doubt that any slight difference in BC between the two bullets is going to result in any perceptible difference in trajectory/wind drift at the ranges any 9.3mm cartridge will be used.

I thought the 9.3x62 was the new IT cartridge in F Class....

The Nosler BCs that were "optimistic" were the initial listings for the AccuBond Long Range bullets. This happened because Nosler (like many other hunting bullet companies back then) came up with BCs by chronographing ammo both at the muzzle and downrange, though not very far downrange. They'd then use those numbers to calculate BC. (As I recall Nosler's second velocity was at 200 yards.)

This works okay for what used to be considered "normal" hunting distances, say less than 500 yards. But it doesn't beyond 500, because BC changes over longer distances. Which is why Nosler eventually had the ABLRs tested by another company which specializes in that.

I have range-tested the 250 AccuBond at 2650 fps from my CZ out to 400+ yards, which is as far as I've ever shot it at game, and the listed BC work s out to that range. But if you're planning to shoot at longer ranges, the listed BC probably won't work way out there.

Mule Deer: the voice of reason and sense in a world of over thinking.

While not always pragmatic, academic thought experiments to increase one’s understanding are not necessarily “overthinking.”

Thanks Jordan. That's exactly what my OP was about. Seeing Nosler's listing of the same BC for two differently shaped bullets got me thinking I didn't understand BC as well as I ought to, and I reached out to the smart folks on 24CF for some schooling. The fact they were 9.3mm bullets had nothing to do with the question, nor did the question constitute a desire to shoot game at long range with my 9.3x62.
Both your answers, and a subsequent comparison to every other similar case I could find in the Nosler manual has led me to conclude that Nosler simply made an editorial mistake by listing the identical BC for the two bullets.
BTW, I shot the 250 E-Tips yesterday over Varget and they appear to be every bit as accurate as the 250 AB in my rifle. [EDIT: and they are on sale at SPS right now - still in stock.]

Cheers,
Rex

Concur, John. Just trying to learn a little more about the factors that constitute a bullet's BC.

Has anyone used those 9.3 e tips on meat?.mb

Haven't used the 9.3, but have used various other E-Tips from 6mm to .30 caliber quite a bit, and have never been able to tell any difference in on-game performance between them and TTSXs, whether in penetration, "killing power," or meat damage.

This is useful, thanks much.

Might be worth noting that Nosler underestimates the BC of some of the .358 accubonds by a fair bit. It's possible they are not subjecting these "shorter range" type bullets to the same testing that they put the ABLR type bullets to, because within the bullets expansion window, it matters less. Plus twist rates can vary a lot for the medium bores. Anyway I'll be interested to hear what you find for real world BC on the e-tips.