ballistic coefficient questions . 6.5 mm bullets

[MontanaRifleman]

G1 bc's are very velocity sensitive, but that is because of the model used to calculate a G1 bc. G7 bc's are much more stable because the model used is closer in form to modern streamlined bullets. Bryan Litz has written some pretty informative stuff on that subject, if you care to have your head spin a bit.

The problem, as I see it, with the CE 130g bullet is two fold:

First, most factory 6.5's come with a 9 twist. That means, if I want to shoot this bullet, I have to have a custom barrel. Now, it is said that the 140 class VLD's also require an 8 twist. However, I have found them to shoot very well in my 9 twist rifles. Go figure. The only way I found that out was to try them. However, at 3-4x the cost of Bergers or AMAX's, I am reluctant to experiment with these bullets. I might feel differently if there were a gain in performance to be had, which brings me to my second point...

Secondly, even if we accept CE's bc numbers, which appear almost certain to be optimistic, the CE 130g bullet will not shoot as flat as the conventional 140 VLD's at long range. Yes, the 130 may be able to be launched a bit faster, but that difference won't hold up as the range increases. So, in the balance of bc/velocity, we have a tie, at best.

Yes, the CE is more likely to perform better than the VLD's at shorter ranges where the impact velocity is still high. But, there are already bullets like Barnes, GMX, and E-Tip that do this just as well and at less expense.

To me, the CE bullets in the smaller calibers have two possible advantages over other bullet designs:

1. They offer a one bullet solution for close and long range shooting. However, close range terminal performance is still gained at the expense of long range ballistic performance. The loss of long range ballistic performace will just be smaller than with other mono metal bullets.

2. If you have a rifle/cartridge case combination that is capable of driving conventional 6.5mm bullets fast enough to make them come apart, the 130 CEB is the best of all possible worlds for you. Its monometal construction will eliminate bullet blow up in flight and give good terminal performance on impact and it will do that with the best bc obtainable in a monometal bullet.

The kicker, IMO, is that neither of the possible benefits of the CE bullets are going to be realized at the velocities produced by any 6.5 cartridge from the .264WM on down. Especially with the short action 6.5's, there is no advantage at all to shooting this bullet.

So, unless you are shooting a 6.5STW or a 6.5-300 Wby, I don't see an advantage to these bullets. And, for 3x the price of Bergers, you are going to have to show me a pretty decisive advantage to even interest me in shooting them.

For .338 and up, these bullets offer performance increases that cannot be had in other bullets. It doesn't look to me like those benefits translate to the lighter calibers, however.

For the most part I agree with you. These bullets are best in higher velocity cartridges. The advantages of the CE bullets are they are bore riding bullets and they will get higher velocities than other bullets of the same weight. Increased velocity is like increased BC. Shooting a .53 BC @ 3450 is about the same as shooting a .55 BC bullet @ 3400 to 1K.

Their design also makes them very accurate in most barrels. No fussing with seating depth. I've only tried the STD 180's in my 300 RUM, and they were much more accurate than 180 E-Tips and 210 Bergers which were fairly accurate. If i can print .4 MOA @ 1K with them vs .8 MOA with another bullet, that makes them worth the price to me. If not, then maybe it's time to reconsider.

The thing that concerns me about the Bergers and similar type bullets is the potential for massive meat damage at higher velocities, so this is another reason to like the CE's, but a bullet like an E-Tip would be cheaper, but the CE definitley has a better BC than an E-Tip.

 

[Cold Trigger Finger]

I'm definatly not knocking CA bullets. Or any other brand for that matter .. Cutting Edge probably researched which bullets would sell the best and made those bullets. .

In my situation with the game I hunt with a 6.5 I need a bullet that works to 700 yards or less in the rifle. Longer shots will prolly give a guy time to change ammo.

It would be nice to have a One bullet does all. . It seems the larger bullet makers came up with a compromise of 120 gr mono bullets with a BC well under. 500 .
Perhaps because of the 9" twist. No wonder Jim Charmichel. (Sp) got p.o.d. at Remington when they brought out the 260 with the slow twist. At least Hornady got it right with the Creed .. I wish they would come out with a 130 GMX with a BC well over. .500 for the Creed.

I really appreciate everyone's input in this thread. I'm learning LOTS.

 

[Beng]

Longer shots will prolly give a guy time to change ammo.

Do I understand correctly, that you want to switch loads in mid hunting without cleaning, refouling and rezeroing and then shoot at 700 yards at a living beeing?

If you want a rifle that is good for all north american game at short and long range, then use a .30cal+ magnum cartridge.
Too big does kill, marginaly too small wounds.
Use a rifle and cartridge that maximizes your margin of error by maxizing penetration and minimizing wind drift.
.264 is a nice little caliber, but not suitable for beginners at long range hunting.

 

[Cold Trigger Finger]

The only animals I will shoot at at long range are predators. Primarily wolves it can't be that hard is it? ?
How do military snipers deal with targets at various ranges? And a lot of them are using 308 Win.

I would quit shooting a rifle if I had to shoot a 30 cal I think. Yuk! !!!!!!!!

Now the 338 is a truely useful caliber. But I don't want to explode a fox with one .

 

[benchracer]

For the most part I agree with you. These bullets are best in higher velocity cartridges. The advantages of the CE bullets are they are bore riding bullets and they will get higher velocities than other bullets of the same weight. Increased velocity is like increased BC. Shooting a .53 BC @ 3450 is about the same as shooting a .55 BC bullet @ 3400 to 1K.

Their design also makes them very accurate in most barrels. No fussing with seating depth. I've only tried the STD 180's in my 300 RUM, and they were much more accurate than 180 E-Tips and 210 Bergers which were fairly accurate. If i can print .4 MOA @ 1K with them vs .8 MOA with another bullet, that makes them worth the price to me. If not, then maybe it's time to reconsider.

The thing that concerns me about the Bergers and similar type bullets is the potential for massive meat damage at higher velocities, so this is another reason to like the CE's, but a bullet like an E-Tip would be cheaper, but the CE definitley has a better BC than an E-Tip.

If you are getting .4 MOA @ 1000 with CE bullets, I don't blame you one bit. I would keep shooting them too!

What kind of velocity difference are you seeing between CE bullets and same weight conventional bullets? I remember reading LTLR's posts on his results with the 225 CE's in .338 and he mentioned this also. I am curious to see if the velocity gain turns out to be consistent with these bullets.

The seating depth thing doesn't bother me. I have never needed more than 20 rounds to get it figured out. So, when loading the CE bullets, do you go straight to finding your best powder charge?

 

[benchracer]

Do I understand correctly, that you want to switch loads in mid hunting without cleaning, refouling and rezeroing and then shoot at 700 yards at a living beeing?

If you want a rifle that is good for all north american game at short and long range, then use a .30cal+ magnum cartridge.
Too big does kill, marginaly too small wounds.
Use a rifle and cartridge that maximizes your margin of error by maxizing penetration and minimizing wind drift.
.264 is a nice little caliber, but not suitable for beginners at long range hunting.

Unless you are hunting your big game by the herd, there is no reason to clean, foul, and rezero while switching loads. Maybe your rifles are that finicky. Mine aren't.

 

[MontanaRifleman]

If you are getting .4 MOA @ 1000 with CE bullets, I don't blame you one bit. I would keep shooting them too!

What kind of velocity difference are you seeing between CE bullets and same weight conventional bullets? I remember reading LTLR's posts on his results with the 225 CE's in .338 and he mentioned this also. I am curious to see if the velocity gain turns out to be consistent with these bullets.

The seating depth thing doesn't bother me. I have never needed more than 20 rounds to get it figured out. So, when loading the CE bullets, do you go straight to finding your best powder charge?

.4 vs .8 was just a hypothetical example. If I don't get the significant difference in accuracy, I would weight the cost of the bullets a lot more. I have only shot them, 180 STD, for initial load development in my 300 RUM and they showed excellent accuracy. They showed about 50 fps better velocity than 180 E-Tips. Yes, I go straight to best powder and charge results. No seating trials. They do not have a traditional ogive that engages the lands. The bore rider is ideally seated into the lands with the driving band and sealtite band right behind.

I have a 6.5 WSM in the work and Outlaw has already used the 6.5 130's in his WSM with good results. With an overbore like the 6.5 WSM, you don't want to spend a lot of time finding the right bullet, the right powder and the right seating depth. My plan is to develop 1 load for the CE's for hunting and another load with maybe Bergers for other shooting.

Yup, I read LTLR's thread and liked what I read which confirms my limited experience with them.

 

[Cold Trigger Finger]

It seems the German's and Sweede's had the moderate velocity 6.5 twist rate figured out a long time ago. 1 in 7.7 .

 

[benchracer]

.4 vs .8 was just a hypothetical example. If I don't get the significant difference in accuracy, I would weight the cost of the bullets a lot more. I have only shot them, 180 STD, for initial load development in my 300 RUM and they showed excellent accuracy. They showed about 50 fps better velocity than 180 E-Tips. Yes, I go straight to best powder and charge results. No seating trials. They do not have a traditional ogive that engages the lands. The bore rider is ideally seated into the lands with the driving band and sealtite band right behind.

I have a 6.5 WSM in the work and Outlaw has already used the 6.5 130's in his WSM with good results. With an overbore like the 6.5 WSM, you don't want to spend a lot of time finding the right bullet, the right powder and the right seating depth. My plan is to develop 1 load for the CE's for hunting and another load with maybe Bergers for other shooting.

Yup, I read LTLR's thread and liked what I read which confirms my limited experience with them.

Thank you! That is all good information to know. Now I'm amped up about starting load development for my .375 when I get home. I can't wait!

 

[parshal]

Most manufacturers do overstate their bullet's BC's. Bryan Litz has tested many of the popular bullets and printed the results in his books, Applied Ballists. In the first volume he lists the 130 Scirocco with a G1 BC of .491 averaged from 3000 to 1500 fps.

I apologize for resurrecting an old thread but I thought this might notify the posters here. I'm specifically looking for the Scirocco II and the real world BC in Bryan's book. Does anyone have the second edition or know if the above info is for the original Scirocco or the II? I'm shooting this bullet at 3250 at 6000 feet. I know Swift tests their BC at 100 yards. At least they did when they ran a test for me.

At 700 yards, the difference between the published .571 and the .491 quoted above is 4 inches.

 

[Mikecr]

The .491 is a logical average falling from 3kfps MV, probably under ICAO conditions(SL, 29.92"Hg, 59deg).
Now add std conditions at 6000ft(38deg, 24"Hg), the same bullet goes to .587 and another 250fps beginning adds ~.007, so you're looking at .594 for a local BC.

Be sure to test it

 

[parshal]

Thanks Mike. Do you know if the bullet in the book is the original Scirocco or the Scirocco II?

 

[Mikecr]

That distinction is not made in the 2nd edition book. So I don't know.

 

[parshal]

I think the Scirocco II was out before the 2nd edition so I'd guess it's the II in his book.

That Puts the Scirocco down around the 130 Accubond with 488 although I'd guess that is actually lower as well. Is the 130 Accubond in Brian's book as well?