sub caliber or chamber inserts or auxilary caliber

Anyone ever used these, they have been around for a long time. I tried the 303 chamber insert in 32 acp and 32 S&W in a few early Mark 1*** rifles, a few were very accurate at pistol range distance. The 32 acp was better with the jacketed bullet. Also tried the 30-06 in a few four digit Springfield 1903 rifles, the 32 acp was a little better too. The 22 rim fire in the 223 chamber insert has a small firing pin inside. It works very well in my AR-15, I just do not like extracting the steel insert. You could ream the 303 or 30-06 insert to use the 32 S&W long. They make a 30-06 insert chambered for the 30M1 carbine too

Once I thought it a good idea to have a .410 insert for my 12g shot-gun. Think I've used it about once in 40years. Now ... if I had a .32" pistol then an insert for my .303 could be a bit of plinking fun, but I don't. However, for a bit of short range practice I could be tempted to fill some .303 brass with a high volume powder (Red-Dot ?) topped off with .32" fmj's. I suspect they could be cheaper, more accurate and may even mag feed !

8mm Lebel with the spherical ball for reduced loading at 15 meters. Better than a sub calibre insert but only in cartridge collections now.