I get it that you are not doing this because it has any practical reason .
Its simply because you want to carry out your own creation and learn a few things along the way.I do not intend to encourage/discourage you.Thats all up to you.
Suppose you do not sleeve another receiver in as I suggested.
I'll offer you another approach.I do not know how many other problems it will create.I'm sure there will be plenty!
Think about your bolt face,magazine feeding,and rotating the bolt.
From the center axis of the bolt,The magazine must be postioned a specific distance from that axis,and a portion of the bolt must clear the feed lips,yet strip a cartridge,Then the bolt must rotate 90 deg,without interfering with the mag lips.And,someplace you must design in extractor(s).That means,pretty much,that the bolt must be machined down to approx. .22 rim dia from 3oclock to 12 oclock.I mean for 270 degrees.Only 90 deg,from 12 oclock to 3 oclock,can remain the the .700 bolt body dia fom the breech face back to the rear of the magazine.I don't even want to talk extractor at this point.
You will note most 22 bolt guns have 2 piece bolts with non rotating bolt heads.
A non rotating bolt head solves a lot of problems.
So,maybe you could extend the barrel receiver tenon back to flush with the rear of the receiver ring.
You will not use the forward locking lugs for locking.They will simply be the "keys" to orient the clocking of the bolt head,so it does not rotate.
You will cut the bolt body to make a two piece bolt,with a new bolt head.
There is a third locking lug on a mauser bolt,at the rear of the bolt.The safety lug.Between that and maybe the bolt handle against the receiver ring you can achieve a lockup.I'm not sure how for and aft positioning of the bolt will mess with trigger function and design.(Update,if its not a 98,it may not have the third lug.You may be stuck with using the bolt handle.Even if you had to weld a little buildup on the root of the bolt handle,it does not take much to hold a 22 lr locked closed.)
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Now that you are making a new stubby little bolt head,you can offset a firing pin location to rimfire in the bolt head,and probably shorten and alter an existing mauser striker to rimfire.Remember,you extended the barrel tenon,so the breech face has moved back to flush with the rear of the receiver ring.That means a shorter striker/firing pin.
I do not know if all that will work.Its just a cartoon in my head.
An alternative path might be something like a 45 acp conversion.Centerfire,same bolt face and extractor.Make a block to go in the guard assy to take 1911 mags,and move the bolt stop /ejector box fwd with a little creative weld buildup.Essentially making a"short stroke" action.
Heck,.460 Rowland.An Officers model or compact 6 shot or so mag may not protrude too much past the guard.ncorporate a 1911 mag catch in your mag adapter block.
Numrich used to sell a 16 in 1911 bbl and there was a Mec-Tec carbine.You may be able to scroung some carbine length 45 bbl with a pretty much cylindrical OD,so maybe you could sleeve it into a junk military mauser barrel.Even just through the first step of the stepped mauser barrel.Its about .750 OD.
If you go that route,be carefull about barrel length.Even messing with a 1911 bbl hood may shorten the bbl to less than 16 in,causing NFA problems.
