platform:
I immediatly thought of shell shrinkers or cartridge adaptors. I have used a .22LR adaptor in .223 rifles. Accuracy was not all I hoped for but minute of soda can to 50 yards and not the same Point of Aim as for the .223 cartridge/
I have also used a .308/ 7.62 NATO to .32 ACP shell shrinker. I found that with some ammo and careful loading that this could be accurate enough to take small game with the .308 using .32 ACP in a pinch and a good bit less noisey than .308 loads. That in a Savage 110.
The adaptors for rim-fire tend to be a PITA to use as they include a seperate piece for a firing pin adaptor and this can be dropped out when loading the adaptor or when ejecting it relatively easy. As the adaptor must be removed after each shot, the firing pin piece removed (or found) the old shell case ejected with a rod of some sort the adaptor reloaded the firing pin piece re inserted and held in as the adaptor is loaded.......rate of fire is Glacial.
Many moons ago the USian gubermint made such adaptors for the 1917 and 1919 Machine guns for short range training they differed from the ones I use in a .308 in that they were .22 LR and the adaptor that looked like .30-06 cartridge with a long blunt bullet on it had a rifled section and launched a .22 LR bullet through the bore of the .30-06 barrel with no contact between bore and bullet. Those are pretty rare.
Back when bolt actions were the standard military rifles world wide there were a host of .22LR training rifles built to mimic their full power brothern to allow relistic and inexpensive practice and training.
Springfield Armory (the US government one) made .22 LR versions of the M1903 rifle, though most were set up as sporters. One of those would cost you CONSIDERABLY more than $500 so lets forget that.
A lot of folks around here love the M91/30 and later Mosin Nagants. Well the countries that used those sometimes made .22LR versions of them though again with more of a sporter look to most of them. THose are still floating around, and likely the cheapest of the trainign rifles like their big brothers.
The UK made .22LR versions of the SMLE, genrally single shots with an empty magazine box that caught ejected cases.
The Germans produced .22LR versions of thier M98 Mauser rifles between the wars such as the KKW. These had the same layout and look of the service rifles though some were made as sporters. SOme were produced as Zimmer Shutzen rifes using the 4mm rimfire for shooting indoors like say in your living room. Some of those 4mm might be a problem in the US as they featured a built in suppressor of sorts that realy did reduce the sound of indoor shooting below the already low report of the 4mm. I believe the French continued to manufacture a .22LR version of the M-98 while they were building the K98k immediately after WWII and seem to recall some of these were imported in the 1990s.
Erma between WWI and WWII made a .22LR conversion kit to convert a M-98 Mauser to .22RF (also 4mm models were made) . In these the bolt was replaced by the device which had its own bolt and a full length rifled barrel insert that fit in the M-98's 7.92mm bore. I believe they may go for more than the M2 Springfield versions of the M1903 these days.
If you want a military caliber rifle easily converted to .22LR, then you may need to go with a semi auto. There are semiauto conversion units for both the AR-15 series and the Mini-14 rifles available for around $200, of course you have to shell out the bucks for those rifles first.
Neatest such conversion I ever used was an HK .22LR conversion unit in a German G3. Unit included a barrel liner that fit the 7.62 NATO bore and a unt that replaced the bolt and carrier unit. It used 15 round magazines built into 20 round G3/ HK91 magazines. Pretty darned accurate and as you may guess pretty darned expensive unless you are shooting one supplied by the Bundeswehr with their ammo with a bunch of reservist compeating for beers at a Shooting House.
An aquentince has wondered if a common enexpensive single shot .22LR rifle might be made into a conversion unit for a .30 caliber and up bolt action......that he even thought of this indicates entirely too much time on his hands. He does have his own machine shop and is a manufacturer of firearms and accessories. It may be doable for himself, but I imagine his machine time and own hourly rate would make the price unattractive to most. Still, looking at the old Erma kits and then looking at a Marlin single shot make one go Hmmm.
Good luck with your search.
-Bob Hollingsworth
