Alf,
do you recall this Weatherby round?

http://s73.photobucket.com/use...edia/220R-1.jpg.html

...A blown out 220swift with Wby double radius shoulder,no belt.

Improved 220 Swift of 1945
Beltless not based on a H&H belted case
Was actually not known as the 220 WBY but the Weatherby 220 Rocket.

The odd thing about the early H&H cartridges were that they were not based on common american bullet sizes but euro bullet sizes.

So a 7mm was not a 284 but rather a 7.25mm and the 240 apex or 240 H&H was not a 6mm but a 6.2mm .245 ie larger than the US .243.

H&H's 275 was also not a true 7mm.

H&H's 244 was not designed by Holland and Jones but by a guy by name of David Llewellyn Lloyd.
This was based on the full length H&H case and not the shorter 400/375 case

Could it be that the demand for a high performance .308 caliber cartridge was stimulated by the .30 Newton, invented in 1913, whose ballistics the .300 H&H closely resembles?

Was it because of the 30 Newton ?

If velocity only was the criterium who knows.
Was the Newton a item to pursue ?

Again one can only pontificate
The 30 Newton was really an odd duck and not one that I think many would pursue. ( only +/- 600 rifles were made in this caliber)

The case it was based on was the 11.2 Mauser with it's heavily rebated rim. That in itself is a problem child. All the pictures I have seen from collectors and there are very few examples, all seem to show season cracking of the necks ... perhaps because of the old DWM cases
There was a connection between Speer and DWM at the time.

The bullet size on the 30 Newton is a .308 ie 7.8mm

I happen to have an original Model 1916 Newton rifle in caliber .30 Newton and the brass can be formed from 8X68S cases. Not all that unusual after all.

There were more .30 Newton rifles made than .505 rifles by Gibbs. Factory ammunition was available until the 1930's.

The .30 Newton was the only factory loaded .30 caliber Magnum cartridge available before the advent of the .300 H&H. I was merely suggesting that its success, such as it was, may have inspired Holland & Holland.

The 1916 Newton rifle did not perish from lack of demand, but from lack of barrels during World War I. Newton had previously relied on German suppliers and that source was cut off by the war. Many of the rifle's features lived on in the Model 70 Winchester.

The .300 H&H might have languished as did most of the other H&H cartridges, had Winchester not brought out a version of their Model 70 in that caliber, and had Ben Comfort not won the Wimbledon Cup, fired with metallic sights at 1000 yards, with a target rifle in that caliber.

Back in the 60's, when I started competitive high power shooting, one of the most popular 1000 yard cartridges was the .30-.338, otherwise known as the "belted Newton" from its similarity to the original .30 Newton cartridge. It was among the earliest of the "short magnum" cartridges, which had the advantage of its namesake of being adapted to standard (.30-'06) length rifle actions,