I would like to know how to turn a std.7x57 into an improved case with a :
neck length of .284" (std. .378")
Shoulder dia .455"
Shldr angle 30deg.

Should one fully neck up a 7x57 to .30cal,followed by necking back down to 7mm@.284" length(for .30cal ghost shoulder to fireform off),or
Would you just neck down a 8x57 to 7mm(.284"length)then fireform?

Whats the magazine/action length?

Take a chamber cast to see what it's neck diameter is. If is the same or less than a 7mm RM that should clean it up otherwise.

Can the barrel be set back?

Finally whats the rifle like and how does it shoot now? This is the old don't fix it if it ain't broke question.

Savage99,
it is not rechambering anything,it will into anew barrel.The magbox is 3" M70SA. The idea is to get the most out of the 7x57 case in a SA,without going to the much fatter.284win or shortmags.I also dont like their shoulder angles.

I just take a cheap long bullet and jam it into the lands. If you want the most and don't have the reamer yet shorten the neck. There is nothing majic about one caliber.

There is the S99 line of wildcats that I thought up in a delusional moment. Get a reamer that lets the mouth of the case be the intial headspace and form it out of say a 30-06 case or as you mention a 8x57. Then you can do the final fireform with good bullets. Necks pull back on fireforming as long as it's sharper than before. You did mention 30 degrees.

The 284 is only about .027" larger in base diameter. There is also a .376 Steyr case.

One more try at sanity. For the cost of these types of projects one can buy another gun and then have two guns! Then you carry the big gun where it's best and the small gun.........

i neck down 30-30 brass to form 7-30 waters cases with no problems. with a tapered expander you could neck up to .30 or on up to 8mm, than neck back down to 7mm; depending on what gives you the best result.

woodjack

It's amazing how such a simple question can generate so many complicated answers.

Either way that you described would work fine. It just depends on what brass you have. One advantage to using the 7x57 is that there is some very good brass available in that caliber. One thing i would not do is seat a bullet long and jam it into the lands hoping that will result in good cases. It might work and it might not. JMHO

Ray

Well I have been using the bullet to headspace for 25 years. Never had a problem. Taking 280 cases up to 375. Either of your ways will work have at it.