Hello David, i fully agree if accuracy is the main concern, but if making sharing reloading data is your aim (as a maker) it is my understanding that it could hold some relevance, as the varying throat length of different 7x57s can make it a bit more tricky with regards to finding a recipe that works more easily across a different array of x57s.
But i am only about to start my reloading adventure now, so i guess i shall soon find out in practice.
I really wouldn’t worry about various throat lengths when reloading.
When you work up a load you are working a load for a specific rifle, and part of the process is making sure the bullet is not being jammed into the lands.
Any factory made 7x57 will be made to SAAMI or CIP specifications. Custom rifles may not be, and this implies to lots of other calibres as well. The 7x57 and 7x64 both have long throats as many of the bullets used were more round nosed in shape.
There is the 275 Rigby HV, which has a separate Saami spec. It’s to all intense the same as the 7x57, only difference being the angle from the chamber to start of rifling. Same cartridge overall length though. Any 275 Rigby HV will be marked as such and was designed for a 140 grain bullet at 2800 fps loaded by Kynoch. But they still shoot the long round nosed bullet but sights may not be regulated to this bullet.
When reloading hunting ammunition I load to standard cartridge overall length and apply a crimp to the cartridge. Two reasons.
1) Hunting ammo goes in and out of the rifle, pockets and is bounced around etc. I do not want that bullet to move in the case.
2) A crimp gives very definite neck tension which I gives a lot of consistency and thus accuracy. And it covers a multitude of errors.
But I am expecting lots of incoming, and note I said “hunting” ammo. A lot of serious reloaders will spend a lot of time adjusting the length of the bullet in the case, applying different neck tensions etc etc. This may make the difference between winning a match and picking up silverware, or doing the clearing up whilst others celebrate.
For me, I want a load that puts the bullet through the vitals of any deer, boar or fox, that has a trajectory where I don’t have to worry about range or wind, or for that matter the exact angle that the deer presents.
Going back to the 7x57 Load data, and for that matter factory ammo, there are two schools of thought:
1) its a 130 year old cartridge that may be shot in a 130 year old rifle so its loaded, or the load data provided is to pretty low pressures and anaemic velocities. Think 140gn at 2500 fps - think Federal blue box, Remington green box.
2) or its loaded to full pressure for rifles in good order of more modern manufacture. The likes of Norma and RWS ammo are loaded as such. Indeed Rigby loaded their 275 HV 140 gr at 2,800 fps.
When loading for any rifle you do need to work up a load keeping in mind pressures etc and the vintage of the rifle. But no reason why a modern 7x57 shouldn’t be loaded to modern pressures, but don’t put that through an old 1893 Mauser!!!
