Cartridge Conversion Sleeves - 'Chamber Inserts:

These fairly cheap tools let a shooter fire a smaller round in their larger chambered firearm.

This image illustrates how a .32" ACP "mouse-gun" round can be inserted into a 'chamber sleeve' (center) and fired perfectly well from a British Lee-Enfield SMLE bolt action rifle.

 - This is because the barrel bore of a .303" is the same size as that used by a "Thirty-Two" pistol .. it's actually also the same size as the Russian AK-47 7.62x39mm & several other widely used calibers such as Nagant Revolvers and some "30 Caliber" rifles.

That useful type of conversion only needs a chamber insert to locate the smaller round in-line for firing through the existing barrel and has a good chance of retaining decent accuracy.

 .. But there is a second type of conversion sleeve that has both the new chamber and a short section of barrel to direct the sub-caliber round down a larger bore. - For example you can find adapters that work by allowing small .22" rim-fires to be shot from a 12 Gauge Shotgun:

There are various clever combinations of "before'n'afters" made and they are fun & interesting to play with .. but do they work properly? ... well they are certainly safe to use and if this system lets you extend your choices that's great - but such a gizmo may or might not be repeatably accurate in your gun.

The latest clever chamber adapter that I have seen permits ten rounds of .22" long-rifle to fire simultaneously from a 40 MM grenade launcher (1.57 inches caliber)!

You can also buy a quite different conversion to convert popular center-fire semi-auto pistols to chamber and run on .22" Rim-Fire ammo. These can be very successful as they include new magazines, barrel and slide .. I have seen these conversion kits made for Glocks and M 1911 pistols and they can be very useful for training.

I have used my Advantage Arms .22" conversion kit in a Glock 17 on the club range while shooting informal "shoot what you got" IPSC Practical matches .. great fun practice and 'experimental' as we shot the same courses comparing various handguns - 38"s, 9mm, 'two-two', 327 Fed-Mag, etc.

I've pretty well concluded that a dedicated caliber gun best suites me .. My experience suggests that when you seek a specific function .. you'd best choose a system designed to produce that result - rather than buying an alternative option .. unless you're easily persuaded by sales talk.

Marty K.
After researching & writing 1,167 blogs .. I've signed-up to Patreon. - In over five years I've not made one cent from this .. NOW you can send me a wee support $ - starting from $1. to get all this stuff from New Zealand - over a year that's nearly the price of one Shooting magazine.

https://www.patreon.com/user?u=16618870