I won't go so far as to say impossible, but I will say very technically difficult and even more so legally.<br><br>In the US, shoulder arms that are rifled must have a barrel of over 16" in length, as per the National Firearms Act of 1934, or be classed as a Destructive Device, onlong with light cannon, sawn-off shotguns and stocked pistols. So this would entail a 16"+ long chamber and barrel adapter to be legal. The barrell insert would be paper thin, and would have to be both strong enough to take rifling and soft enough to not damage the rifling of the main barrel. Fragile, no mater what it was made out of. Then you'd need something to transfer the energy of the centerfire bolt to a rimfire adapter. (The way swappable rifles and pistols do this is by using either a replaceable hammer or bolt, or by using a selectable position firing pin, like Tompson/Cernter does on the Contender. I've seen one such adapter for .223 at a gun show, but I question it's ability to transmit the energy of the firing pin reliably.)<br><br>Delicate, expensive, bulky and mechanically complex- not good solutions. Your best bet may be to see if you can have someone machine up a brass cartridge body with a rifled steel insert (Talk to your national firearms regualtory agency, the ATF in the US; I'm not sure about the legal issues of the rifled section- they may rule it a barrel!) that forms the first inch or so of barrel and the chamber for one the older .30 cal pistol rounds. The base of this would have the exact profile of the base of the cartrdige the adaptor is for, so that it can be ejected/extraced normally. <br><br>My first thought to which calliber would be the .30 Luger cartridge. This is basically your standard 9x19mm necked to take a tiny 7.62mm bullet in the 80 to 100 grain range, that lists from a 4" pistol barrel as being the 250-300 foot-pound range. The other option is to use the 7.63 Mauser/7.62 Tokarev (they are usually intergangable interchangable, except for some early Mauser ammo that is a century old now; the difference has to do with early pressure levels for the Tokarev) which can go up to a 110 gr bullet, and puts out about another 100 foot-pounds, and is a little easier to find if you don't handload. The straight .30 Carbine could work, but the other two are bottleneck cases and can space off of the shoulders, which would be easier to build. 30 Carbine is ballistically in the middle of the Mauser and Lugar cases, but might be the easiest of the three rounds to buy commercially in the US. It's poor rep comes from is lack of ability as a manstopepr, not as a bunnyslayer.<br><br>.32 ACP uses a .309 calliber bullet (the .308 and .30-06 use a .308), but it might be technically possible to do this if you are using a .30-30 or a Chinese/Warsaw Pact manufactured 7.62x39 firearm (both use bulets closer to .310-.311 than to .308) if you are willing to accept reduced accuracy. I would caution strongly against this becuase of the possibilities of a western arms maker producing a 7.62x39 that actually uses a .308 bore, but I don't know about the credability of those rumors (mostly having to do with early Ruger models). IF it can be done, the ammo is almost universally available outside of places former USSR and the PRC for very little money, but it probably the most anmeic of the four that's I've mentioned. I'll also state that my grandfather used to carry a Walther PP in .32 as a kit gun, and shot plenty of small game for the cook pot while he lived in Africa with that gun, so for small meat it should be fine.<br><br>In any case, you MAY be able to get sub-calliber adaptors that do this commerically. I know they used to be made, I've seen ads for them that date back 20, 30 years, but nothing more recent than a magazine from the early 80s. If you scrounge hard enough, you may be able to find a used one, but I don't know if they ever worked as well as advertised or if a used one would even be safe.<br><br>Your other options might include playing with handloads, if that bug has bitten you, but do so at your own risk. (If I may, I suggest the military steel cases for that experiment, even if they are only a few hundredths of the percent point stronger, they usually have thicker case walls and thus less internal volume, so tehy MIGHT be a TINY bit safer.) Or you could go hog wild and buy small capacity cases that are nothing more than cartridge machined from a block of brass that has the right external dimensions and a tiny capacity equal to a pistol cartridge. But there you are talking about a maybe a $100 for a cartridge case.