470 win mag

[Jefferry404]

@Ray B
Good question.
I was not sure if the 470 Winmag was actually 470 caliber, .468 was the closest, or he meant 470 as in 470 Nitro or 470 Capstick, so I modeled both calibers.
I suspect it is .474,475 caliber.
As @rookhawk noted, the Capstick short is a nice cartridge!
As this exercise shows, if the 458 winmag took advantage of the reduce pressure vs x-section area, would have been a better round.

 

[Badboymelvin]

The guy who built this rifle is the same guy that built my 425 Express... and like someone mentioned he's an absolute wizard when it come to this kind of thing.

What I like is that he thinks outside the box and does interesting builds.
Sure, they might not be for everyone, but they're interesting and they get people talking - and the quality of the builds are second to none.

Very knowledgeable guy and I just love reading and watching the stuff he does

And yes, he seems totally defiant to recoil...

Russ

 

[mickb]

The original post said it was a custom 458 Win Mag necked up to 470 for $4200.

If I was going to try to reproduce something like this, I would buy a left-handed Hawkeye African in 375 Ruger that I've been ignoring for $900 to start with. Then I would wildcat it by upsizing the larger-capacity 416 Ruger as the parent case. Seems like I might be able to get similar or possibly better results at a more affordable price.

As a fun side project, I built my Ruger 77 MkII 458 Win Mag for $1,486. It weighs about the same as the rifle above & I really enjoy shooting it. I don't think I would personally spend that amount of money to get the extra 470

Its 4200 Australian , around 2500USD. But again not so much a power/dollars ratio project anyway, more a project that personally interested him

 

[mickb]

Pretty interesting. I always wonder though, by increasing the bullet size we're reducing the velocity with the energy staying roughly the same, typically. Is making a 458 Win Mag into a 470 Win Mag or 500 Win Mag really making an improvement?

One thing I will say, I'm at least grateful to keep things fairly straightforward with this wildcat. The 375HH necked to 458 and necked to 470 seems far less extreme than inventing a goofy case or using rare brass like 404J and trying to neck it up.

The energy doesnt stay the same when you increase bore size though, if thats what you meant, it increases. A basic rule of thumb is the increase in energy as you move up calibre is equal to half the increase in bore surface area.

So a 475 vs a 458 with the same case capacity, 11% surface area increase= 5.5% increase kinetic energy.
Its not a big enough jump to map a lot of difference between 458 and 475 no,... but if you plug in the differences for big jumps like between 375-416-458-500 for a given case family, the rule of thumb usually works out....

The 470 win seems to get some additional case capacity increase by removing the taper as well. Be interesting to see what water capacity to case mouth is.

 

[Jefferry404]

Not sure if my chart posted above. Here it is again showing Velocity, Energy vs Caliber.
Not sure about the 11% number above, more like 0.11% change in bore area.
Anyhow, shows increases with caliber for same conditions.
With no taper and the larger bore, case capacity of the 470 was 100.3 grains.
If any interest, I can post drawing, etc.
Steve

 

[mickb]

475 has 11% more cross sectional area than .458

 

[Ray B]

.458/2= .229; 3.14 x .229 x .229 = .165..
.475/2= .238; 3.14 x .238 x .238 = .178
.178 - .165 = .013
013/.165 = .079
.013/.178 = .073
The .475 has 7.9% greater frontal area than the .458
The .458 has 7.3% less frontal area than the .475

 

[Jefferry404]

thanks for correction Ray. I mistakenly took the square of the difference rather than the difference of the squares.

 

[mickb]

.458/2= .229; 3.14 x .229 x .229 = .165..
.475/2= .238; 3.14 x .238 x .238 = .178
.178 - .165 = .013
013/.165 = .079
.013/.178 = .073
The .475 has 7.9% greater frontal area than the .458
The .458 has 7.3% less frontal area than the .475

I dont need a maths lesson thanks. The correction would have been fine. Had the wrong two calibres in mind. And we should call it cross sectional area, not frontal. Frontal would incorporate the projectile nose shape.

 

[AZDAVE]

Ray thanks for laying out the math as when you don't use it all the time people forget the basic algebra.

 

[Ray B]

The problem with terms such as cross sectional area is the basic error in determining sectional density. the error is using the diameter of the bullet squared. this would be correct if bullets were square- but since they are round D squared is wrong, Pi radius squared gives the bullets area. Since D squared is the common calculation for determining sectional density the resulting number is incorrect- but the answer is uniformly incorrect so it works a a standard measure of bullets potential penetration. But in calculating ballistics the correct area on which the pressure is applied needs to be correct.