Feasibility of 5.7x28 conversion of 77/22 Hornet

I've been giving this some thought as I pounded the pavement for hours every day last week. W/o really delving into pressures and dimensions, I think this is a great option. Sort of like an improved version of the Hornet with factory ammo relatively cheap and available.

Both use a .224 bullet, but the bolt face and extractor would be difficult to adapt. The Hornet uses a thick, 0.35" diameter rim, while the 5.7 rimless cartridge is 0.307". The 5.7 is a high-pressure round.

Why limit yourself to a cartridge that only realizes higher velocities by using very lightweight bullets? You don't gain any case capacity over the hornet either do you? I haven't looked up all the numbers. If you want an improved modern version of a hornet get yourself a 221 Fireball and call it a done deal!

"Why limit yourself to a cartridge that" offers readily available, economical, effective ammo? That's where I was going.

I see your point. Ive actually thought about the 22 TCM for the same purpose as what you are thinking.

I can't see a reason why you'd want to do it. Now a 22K-Hornet is an entirely different story.

I suspect the biggest issue with this conversion, as with many conversions, will be getting the cartridges to feed out of the magazine. I doubt the magazines designed for the Hornet will feed a rimless case; I believe the rim is used in these magazines to prevent premature release of the cartridges.

I recently purchased one of these magazine to determine if a .327FM conversion is possible using this magazine. The magazine is closely matched to the dimensions of the Hornet and would need to be altered (wider feedlips, slightly wider rim area) to feed that cartridge; I imagine a cartridge with much different dimensions would be a much more involved process.

The only successful 77/xx conversions I've read about have been 44's to 357 B&D , 357's to 256 Win , and the only successful one where magazine alterations were needed...a 44 into a 45 LC.

The magazine and bolt design (pressure limitations) don't really make for an easy conversion to much in the 77/xx's.

How about this twist? Gut a Ruger magazine and only use the shell as an interface between an FN pistol magazine and the Ruger mag well. That leaves the pressure capability of the action as the limiting factor.

Without a 5.7 mag to take dimensions on, I have no idea whether that setup would work. It might require some modifications to the bottom of the bolt or feed area to pick up cartridges correctly. Are 5.7 pistol mags single or double feed? A lot of variables here.

Re: pressure capabilities of the action, a calculation of bolt thrust from top-end .44M versus 5.7 tells me that the basic action is likely strong enough to handle the increased pressure in a small cartridge like 5.7. I can't be certain that the 77/22 components are similar dimensionally to the 77/44 ones, but given Ruger's manufacturing practices, I'd bet the critical areas are essentially the same.

I did come across some references to a similar action (Savage 40, I think; certainly a single rear lug type action in .22H) being chambered in .223, so I continue to speculate that the biggest hurdle would be making a repeating 77/5.7 feed from a magazine.

Ruger just announced a 5.7x28 pistol.
Maybe you should hold out for a PC Carbine or American Ranch rifle version.

"Maybe you should hold out for a PC Carbine or American Ranch rifle version."

That did cross my mind (high speed left to right) when I saw the ad for the new 57 pistol. Ruger is doing some innovative stuff right now with different chamberings of the common platforms.