K-alterations (best performed in this instance as 260RG suggested) are ok. I wouldn't mind having one myself, but I'm aware that it won't make a .222 out of a Hornet like some Rubes claim it will. The little more velocity gain one can expect won't extend the practical range of the Hornet much beyond what it's good for in original form. What one gets though is somewhat better case life, which is no small consideration in this day and age of Hornet brass shortages. If one is content to shoot loads (either cast or jacketed) in the 16-1800fps range for fun at the range, and hold the full snort stuff for varmint safaris, case life can be virtually never ending even with the standard chambering, making it a fairly moot point IMO. Still and all, like I said, I wouldn't mind having another one.
The only "K" I ever had was an M2 Springfield conversion. Pretty sweet, but evidently not sweet enough to stay in my harem for very long. I probably had my head turned by yet another long-legged vixen...
A gun shop owner friend has a M43 Winchester re-chambered to the K-Hornet for which I think his resistance to my conniving to buy it is waning...
To the OP: I would suss out the reason for excessive headspace before going into any alterations. Bolt set back, perhaps? Also, not being conversant re: M23 centerfires, I'm almost ashamed to ask: aren't their barrels and receivers one piece like on the rimfires? If so, you're pretty much screwed then.
