I've taught a few thousand folks how to shoot, and in order to get them used to Service Pistol and Service Rifle, I've had a lot of use for conversion units in general.
I can requisition thousands of rounds of .22 - but hundreds of service Ball - and getting the shooter used to the feel and sight picture efficiently is of paramount importance, so the light report and non-existent recoil helps new shooters immeasurably.
I use the 'Colt Conversion Kit' from the late '50's - early '60's.
All you need to do to one is use good-quality .22LR and keep the 'floating chamber' greased.
I use ProShot's 'Pro-Gold' and Remington's 'Golden Bullets' and they work perfectly in the Colt, as well as in a Ciener M9 kit and an M16 Conversion Unit.
Now - keep in mind, we're shooting for proficiency and not for speed, so I can't offer an opinion as to what may happen when someone's trying to win a match.
All I can say is that in normal shooting situations - be it 'target accuracy' a'la the National Match Course of Fire - or the 'Killing House' at Bragg - these units have performed quite well.
Remington's 'Golden Bullets' seem to have a little harder coating and faster-burning propellant - important, because the thing that binds up a conversion unit is powder fouling and shaved lead.
An old AMU trick - the Colt 'floating chamber' can be slicked up if needed, by merely breaking the sharp edge of the chamber by chamfering slightly.
Vaya,
Scouts Out!