Hornady 7mm 180g .796 bc

[gohring3006]

180 ELDM @2800 fps 59 degrees. Stability is 1.22
162 ELDM @ 2800 fps 59 degrees stability is 1.53
Via Hornady 4DOF 1-9.25 twist

This tells me no matter what scenario you run the 180 with a 9.5 twist, it will not be as stabile as the 162.

 

[Edd]

Looks to be a long bearing surface...Probably gonna need a 1:7 twist for those.

I'll stick with my 180 & 195 Bergers...

If the bearing surface length changes the twist requirements, a longer bearing surface will likely make the twist requirement slower not faster.

 

[7mmShooter]

Just ran the 180 M vs the 175 X to check stability difference. 1.29 for the 180, 1.35 for the 175. Standard conditions, 2900fps, 9.25 twist.

 

[scdogman]

1.535 inches

 

[scdogman]

Are you guys using Berger which doesn't account for the plastic tip or some other like JBM?

I got the 162-x at 1.57 at 3000fps

I got the 180-m at 1.51 at 2800 fps both using JBM.

StrelokPro has it stable as well.

 

[gohring3006]

Are you guys using Berger which doesn't account for the plastic tip or some other like JBM?

I got the 162-x at 1.57 at 3000fps

I got the 180-m at 1.51 at 2800 fps both using JBM.

StrelokPro has it stable as well.

I'm going off of Hornadys 4DOF, I tend to believe the company's stability calculator when calculating their bullets.

But yea, I talked to a guy who helped with the Miller formula for calculating bullet stability. And he has solid data on the the plastic tip theory. I am convinced myself, but others are not... I would try them and see if you can confirm drop data..

 

[MudRunner2005]

If the bearing surface length changes the twist requirements, a longer bearing surface will likely make the twist requirement slower not faster.

Not doubting you, but if this is the case, then why do projectiles with tangent ogives, short boat tails, and longer bearing surfaces (such as monolithic solid coppers like Barnes) require faster twists than that of equal weight cup & core projectiles with a VLD boat tail design and a shorter bearing surface? I understand it's a different material and copper is more dense, but at the same time weight is weight, and the only difference is design. Does bearing surface deformation play into this? The only thing I can think of different is bullet design.

 

[Edd]

Not doubting you, but if this is the case, then why do projectiles with tangent ogives, short boat tails, and longer bearing surfaces (such as monolithic solid coppers like Barnes) require faster twists than that of equal weight cup & core projectiles with a VLD boat tail design and a shorter bearing surface? I understand it's a different material and copper is more dense, but at the same time weight is weight, and the only difference is design. Does bearing surface deformation play into this? The only thing I can think of different is bullet design.

Copper is less dense so a bullet of the same weight is longer. A longer bullet OAL will require more twist. If the bearing surface is lengthened, that material has to come from somewhere. It will likely come from the OAL length and result in a shorter bullet.

This is not something I know enough about to be teaching. I have read about this and remember some of what I've read. I believe it is in one of Bryan Litz's books. There is a point on the nose of the bullet acts like a lever against the back of the bullet with the bullets center of gravity being the fulcrum. The closer those two points are to each other the easier the bullet is to stabilize.

 

[7mmShooter]

After talking with a few guys over on the hide, oal on the 180 ELD-M is 1.535, bearing surface is .535. I will try and get the tip length as well.

 

[PackersFanboy]

berger 195 1.6490 bearing surface estimate .6770 sierra 183 1.6185 bearing surface estimate .5325

 

[Edd]

berger 195 1.6490 bearing surface estimate .6770 sierra 183 1.6185 bearing surface estimate .5325

Where did you get the .677" bearing surface on the Berger 195 gr? The spec sheet I have shows .524".

 

[PackersFanboy]

Where did you get the .677" bearing surface on the Berger 195 gr? The spec sheet I have shows .524".

correct .524 berger 195 bearing surface looks like it extends out further

 

[B23]

I emailed Hornady to find out what the length of these new 180gr ELD-M bullets will be and this was Jason Hornady's response. I for forgot all about asking what the bearing surface length is so I'll have to email him back on that.

Thank you for the email. The length of the 180gr ELD-M bullets will be 1.540" they will be a great choice for your rifle. 1-8" twist will stabilize the bullet and allow for great B.C.

Thank you,
JH

 

[WildRose]

I think many of us have become drunk on BC's. Yes this is an impressive bullet from the BC standpoint but it's a target bullet, not a hunting bullet.

Shooting target bullets at large game animals leads to a whole lot of serious problems from badly wounded game running off to the opposite, huge gaping holes with massive loss of meat.

The difference in BC between this and any number of long proven high BC hunting bullets won't make much difference even at a 1,000 yards on whether or not you can put it in the boiler room.

It can very much make the difference though in unnecessarily wounding and losing an animal that is hit well or equally unnecessarily blowing huge chunks out of an animal and wasting huge amounts of meat.

Any bullet will do the job on paper or steel, but they won't all give good terminal performance on game.