Whatever, one wrap of thin tape around the head holds the rim against the block for the first shot which also allows the case to expand the secure the position of the shoulder. After that a neck size only is all that you need to maintain the headspace.

I've been necking down GI 30-06 for over 50 years to make 7mm for the Rolling Blocks I've had.   That GI brass is a good bit heavier than regular 7X57 brass and will last a lot longer.   Early on I loaded with 4320 but found that 4350 gave just as accurate and gave better with better case life.   With a 168 grain cast bullet, which I shoot mostly now,  the cases will last almost forever.

George

The two I had seemed to have good head space, but still stretched brass on one side-top side.  I made a mark on the back and always indexed the brass when I loaded it.

I would neck size only until the brass got hard to chamber.  Then I adjusted the sizing die just enough to allow the brass to chamber.  Brass never lasted long. 

The explanation given at the time was the RB action was springy.  The top of the block moved-sprung-flexed minutely, rolling back taking up slack..  Seemed a reasonable explanation at the time.   

DoubleD wrote on Apr 10^th, 2026 at 8:14am:


The breech blocks on any Rolling Block rifles are critical to headspace and often the angles are off even with good headspace! I've seen more than one where a "gunsmith" didn't check the face of the breech block to ensure it was square to the bore when he rebarreled a Rolling Block. Headspace looked great, but upon firing it the rims bent and you couldn't rechamber brass without indexing it the same way it was fired the first time.
Checking the breech block with a used or new barrel screwed in using simple feeler gauges to see if they slide in the same at the top of the barrel as they do at the 6 o'clock position works well. The block face can be milled easily to true it up so the barrel fully contacts the 12 o'clock and 6 o'clock positions equally.

marlinguy said that he had one that was correct. Of course, the 7mm ammo they made back then for the Spanish appears to have been slightly different from the modern.

In the 1950's one of the honcho's at Remington said the 7mm rifles they made back in the day were fine when checked with the gauges they were made to but the headspaces were excessive when checked with the then current gauges. I have a couple clips of that old 7mm ammo my great grampa brought back from the 1898 war and the shoulder is visibly longer than 7x57 ammo of our day.