An old thread, but the idea is still valid. As expensive as .22 ammo has become (and hard to find some places) it's still cheaper than feeding your M1 or M1A and it's easier to teach the fundamentals to a new shooter with a .22 than and .308.
I know it works, too.
This is from several years ago, but it's a testimony to how my 10/22 trainer works for me.
I went shooting with my cousin. I took the 10/22 (set up with Tech Sights, M14 front, M1917 rear sling swivels, a 1&1/4" wide GI canvas sling and butt stock extender to make it fit my long arms better - I even have some 10 round magazines that stick down out of the bottom of the rifle and have a button in them that you push up/forward to operate the mag. release).
I put my shooting mat down, sat down on it and loaded some magazines.
I got down prone, "built" a good sling supported firing position and inserted a magazines and worked the bolt back and released it to chamber a round.
I do what I do to get my NPOA and decided I was ready to fire.
I put my finger in the trigger guard and attempted to move the safety forward to the fire position. What??? Darn, I couldn't believe I'd left the safety in the fire position through slinging up, loading, etc.
I took my finger out of the trigger guard and attempted to move the safety back to the safe position and there was nothing in front of the trigger guard either. I was momentarily stunned.
I raised my cheek up off the stock, to examine my broken M1A only to see it was the 10/22, not the M1A.
Mine works so good for me that down in the prone position, concentrating on the sights, going through the NPOA exercise and preparing to fire a shot - in my mind that 10/22 is a very good substitute for the M1A.
I know people will point out the recoil differences, but really, when you're in the zone, do you really feel recoil? Notice it? Sure. But does it really keep you from doing what you need to do to put the shots on the target?
Just do it. You'll enjoy shooting it. So will your kids, your wife, your friends.