Unknown British Sporting Rifle (.500 3" NE necked to .458)

Hi, I am new to the forum. I joined the IAA in September and this is my first forum post.

In the 1990’s I acquired this British cartridge, which is a .500 3" Nitro Express necked down to .458. I am pretty sure I got it from Jim Tillinghast. I’ve lost the documentation during a move and can’t remember what exactly this cartridge is. I am familiar with most of the British sporting rifle cartridges, but I have not found any reference by searching online or in the IAA forum or in any of the books I have. Could it be an experimental? Can anyone identify it?

Headstamp is KYNOCH .500 NITRO. The primer is flat brass with a dark purple annulus. There is a 3-segment neck crimp close to the shoulder. The bullet is a GM jacketed round nose soft point. Without pulling it I would guess it is a 500 grain bullet. There is powder in the cartridge with a fair amount of air space (at least 1/2" I believe) and it does not sound like Cordite. I have not weighed the cartridge.

Case length: 3.00"
Neck length: 0.41"
Shoulder diameter: 0.524"
Bullet diameter: 0.458"
OAL: 3.906"


Thanks for your help!

Interesting that the knurled crimping cannelure on the bullet is so far out of the case mouth when, as you said, there’s plenty of room inside for more of the bullet. Makes me wonder whether it’s a factory loading. Didn’t see anything in Hoyem, Volume 3 (British sporting rifle) .

Mel, it does seem unusual as you said. But I wonder if a bullet with the cannelure in the “wrong” place could also indicate some experimental load (using an already available bullet)? I’m not sure how common British flanged wildcats are (other than for the .303), since they almost certainly wouldn’t regulate in a double rifle. Although, I guess it could have been used in a single shot as well.

I also looked through all four volumes of Datig without finding anything.

Hello All,
I load for the .458 Winchester Magnum and the bullet sure looks like a Hornady 500 grain solid.
I’m guessing it was an empty case needing a bullet.
That’s my SWAG.
All the best,

Hi Brian,
It’s actually a soft point with a small amount of lead showing (about 1/4" diameter). I used a scanner to get the photo, but it didn’t show the end of the bullet clearly. Not that this rules out what you said.

It’s still a mystery why a handloader would neck a .500 Nitro to .458 when the 500/450 Nitro already exists (but is 1/4" longer with a more gradual neck), though stranger things have been done.

The primer annulus (which appears to me to be factory original) suggests that it at least started as a factory NPE or loaded cartridge. And you can also make out an annealed neck (barely visible in the scan), which would be unusual (I think) for the original straight case .500 NE. So it seems to me that the annealed neck and primer annulus point toward a factory load.


Hi Larry
The case would be annealed and the primer seated and sealed before loading.
British method of loading, safely worked out loading .303’s long ago.

Your 100% right, it is a factory case, but I also think I the bullet is not British but a .458 Win. Mag. bullet. A GM-jacketed bullet, for dangerous game, if British made from this late time would / should have a GMCS jacket.

I don’t think it’s factory either, the bullet and as Mel points out the bullet seating.

Danny gave me a list of chamber reamers from a maker of chamber reamers that I think numbered around 26,000 different that the maker had dimensions for.
Unfortunately or perhaps fortunately the list didn’t list the dimensions, just a name.

Wheel’s seem to get reinvented once a month in the ammunition industry plus hand loaders with imaginations adding to the mix, at least that’s my two pence.

Hi Pete,

I see what you are saying about the bullet jacket (GM vs. GMCS). That did not occur to me.

But I still wonder about the annealing. Would it be normal for Kynoch to anneal a straight wall case (unless it was intended to be necked)?

Annealing allows the case mouth to flex and retain it’s strength when it is under pressure to help avoid stress cracking.
Here is a .450 3 1/4" NE from the same time era. (GMCS bullet)
kynoch%20450%20NE%20oal kynoch%20450%20NE%20hs

Thanks Pete. I could not find an example of a British straight wall in my collection that showed annealing.