Bigedp51's advice is sound.

I used to shoot 7mm Ingram and later 7mm TCU in handgun silhouette matches and the brass is fire formed from a .223 Remington. It's necked up to 7mm, but the shoulder is set too far back and there is too much taper in the case, so it will not head space properly for fire forming.

However, by seating a bullet long enough that it just engages the rifling, you create the equivalent of a "shoulder" to keep the head pressed back against the bolt face and eliminate the stretch that would otherwise occur in the case when you fire formed it.

I found these fire forming loads were almost as accurate as the subsequent loads.

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I use the same approach with the .22 Hornet when loading into new brass or once fired brass that has been full length resized.

The .22 Hornet has significant taper, and a very shallow shoulder angle so all it has to head space on when new is the rim, and cartridges that head space on the rim are notorious for displaying excessive headspace. If the head space is just a little too short in a round that head spaces on the shoulder, most bolt action rifles have enough camming action to size the case enough to get it to chamber. That's not the case in a cartridge that head spaces on the rim as it would have to compress the rim to overcome a too short head space condition.

The end result is that gun makers tend to go long on headspace and cartridge makers tend to go thin on then rim. Both are well intentioned efforts to ensure any ammo and rifle combination will chamber, but the result is often excessive headspace. For a round that is only fired once, the resulting stretching and thinning in the case wall is not a big deal (so ammo makers have no issue with it) but for a hand loader it seriously shortens case life. That's an even more significant issue in the .22 Hornet, given the already thin case wall.

Once you get past the initial firing, just neck size the case. If you only have a full length resizing die, just partially size the case so that you are sizing the neck enough to hold the bullet without moving the shoulder back. However, neck sizing is preferable as it leaves the side walls of the tapered case alone. If you FL resize, you move the whole side of the tapered case back and that quickly work hardens the brass in the sidewall, resulting in spider cracks in the sidewall just below the shoulder where maximum working of the brass occurs.

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For comparison purposes 7.62x51mm NATO and .308 Winchester have exactly the same external cartridge dimensions, but the 7.62x51mm NATO chamber places the shoulder .013 farther forward. That's designed to ensure the round will feed into a dirty chamber, and the brass has a thicker sidewall near the web to ensure it will not separate and will still withstand ejection from machine guns.

However, if you fire .308 Win brass in your 7.62x51 chamber, you'l get .013" more stretch in the case and with the thinner .308 Win case, you end up in the same boat as you do with .22 Hornet.

Consequently, I order my service rifle match barrels with a .308 chamber rather than 7.62x51. In my 7.62x51 Garand which came with a 7.62x51 chamber, and has lots of excess space in the magazine I seat the bullet long enough to just engage the rifling when loading bullets into new brass.