I made my decision - to shoot it very lightly and gingerly to confirm operation, get a feel for how it groups and sights.... and then basically set it aside.
Here are the results of my first two shots from 25 yards, using Winchester 100 grain soft points - not holding a bench rest, but using my elbows on the stand:
I stopped there - for a while - as this really just clinched it for me that this is not going to be my 'plinker', I will be saving for an IAI or more 'standard' M1 for my original goal: semi-auto rifle for short range plinking, possible varminting.
This was hidden upside, and I feel very lucky - a custodian of history.
Next I resolved to test a 10 shot group for overall patterning. I adjusted my aim so that I was aiming the iron sights 4 inches high - basically covering the orange dot... hard to confirm aim like this, but I don't know how to adjust for 25 yards.
Well, here was my first ever 10-shot group out of anything longer than a pistol:
The trigger pull is a little stiff - 5-6 pounds? - and I am still learning how to sight that peeper.
I may shoot her again - maybe once a year - don't worry, though.... I'll go easy on her as I plan on getting that IAI or more 'standard' M1 Carbine soon for some mid-distance fun.
Anyone got one for sale?
Thanks again for the advice. You guys are all really helpful.
-sven