Looks like the first .416 Ruger had a Weatherby-style double-radiused shoulder, and was 2.900" long in the brass.
Sort of a .416 Weatherby without the belt:

From ammo-one.com:
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http://www.ammo-one.com/416Ruger.html






There are two different 416 Ruger cartridges!
(1.) Just issued in January 2009 by Hornady, the 416 Ruger cartridge, which is
basically a 375 Ruger expanded to accept 416 projectiles.
(2.) The first 416 Ruger was limited to 200 rounds, produced by Bell Brass
Company and given to Bill Ruger in 1991 for his 75th birthday.
Ruger Company made a special Ruger "Number One Rifle" for
Bill Ruger's 75th birthday and Bell made the cartridges for the rifle.
The two cartridge are completely different. The 1991 version is basically a
416 Rigby with a slightly different neck angle. The headstamp was
(Bell 16 97 416 RUGER)
As stated, the newer version by Hornady is a 375 Ruger cartridge which is
basically a 375 Ruger expanded to accept 416 projectiles. The headstamp is
(HORNADY 416 RUGER)



The 416 Ruger was limited to just 200
Cartridges. The cartridge was made by Bell
Brass for a very special (No.1) Ruger Single
Shot Rifle. The rifle was given to Bill Ruger on his 75th. birthday in 1991. On the headstamp: the 16 is for 1916, Bill Ruger's birth year, the 97 is the year cases were made , 1997, yes, 6 years after the rifle.
A bit odd, but that is what James Bell said.

Sorry sold out, most likely will never have more, but leaving this web-page up for viewers interested in the item.
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My first though of a wildcat before I began playing with the 500 A2 in the late 1990's was to neck up the .338 Lapua Magnum to .416 caliber.

Nah, I thought, why do I need the better brass of the .338 Lapua Magnum with the slicker 20-degree shoulder of the .338 LM,
instead of the collapsible abomination of the Rigby 45-degree shoulder?
The .416 Rigby has the same huge case taper as the .338 LM, and it still feeds just fine due to that, rather the .338 LM copied the Rigby on that.

But now I have a reason!
It will fit 3 cartridges down in the M70 RUM box with increased windowing!

The Duane Wiebe, XRM box will make it even easier ... Duane is still making that second follower I ordered ... parts pending ...

Another easy .416/.338 Lapua Magnum Rifle, compact and light:

The Ruger No.1 in .416 Ruger, stainless/laminate:
Just clean up that .416 ruger of 2009 chamber with the new reamer, fatter and about 0.2" longer.
Just add ".416/.338 Lapua Magnum" above the ".416 Ruger" on the barrel.
Afterall, it is a .416 Ruger still, a .416-caliber Ruger No.1.

Perfect pair, a stainless M70 .416/.338 LM,
and a stainless ruger No.1.
The Ruger No. 1 barrel is 24", 1:14" twist, and 0.750" diameter at the muzzle, perfect for single-shot accuracy, very portable still.

The M70 could be 1:12" twist, 23", 0.700" muzzle diameter. Downright sporty!

Tough to fit the blown-out shoulder of the .500/.338LM for 3 in the RUM box, but easy with the full taper retained on the .416/.338 LM.

Am I sounding like boom stick or what?

What?
You say stick with the bolt action .416 Ruger Hawkeye Alaskan 20" with heavy bullets for DG,
and the single shot .416 Ruger 24" Ruger No. 1 with light bullets for plains game?
Take only one chambering of ammunition with two bullet weights and know where they shoot in each of the two rifles?
Oh.
OK.