This helps:
Bart Bobbitt on tuning Garand grass ejection:
On Wed, 11 Feb 2004 23:54:27 +0000 (UTC), in rec.guns
bartbob@aol.com (Bart B.) wrote:
"The most common cause of scratched (or dented) cases from an M1 is they bounce off the operating rod near the handle when the bolt's all the way back. What happens is the ejector spring is very strong and as soon as the empty case mouth clears the chamber, the ejector pushes the case head away from the bolt face very fast and hard. As the extractor holds the case head at 2-'clock and the ejector pushes the case out at its 8-'clock position, the case flips backwards over the opening bolt and bounces off the operating rod. Inspecting the op rod hump near its handle will probably show brass colored streaks at that point. Empty cases usually have a tiny dent near the shoulder.
Another indicator is the empty cases are thrown backwards from the rifle at about a 4- to 5-o'clock angle to the line of fire or bouncing off the shooter's glasses or forehead.
The cure is to make the ejector spring weaker. Using an M1 combination tool in the chamber, close the bolt on it, then remove the extractor and its spring and next remove the ejector and its spring.
Using a good, hard pair of diagonal cutters, cut off two turns of the ejector spring. Reassemble the bolt, then fire several rounds. If the rounds aren't ejecting forward at about 2-o'clock from the line of fire, take the extractor and ejector out, then cut another turn off the ejector spring. Try it again. When the ejector spring is perfect, empty cases will pile up about three feet away at the 2-o'clock position. And ther won't be any more cases bouncing off your fore head.
Years ago when on a military rifle team, I was given a couple dozen M1's to take to the function firing range to 'tune' their ejector springs. It took between 2 and 5 turns cut off to get the empties ejecting forward and to the right a couple of feet away. In fact, a friend of mine and I had a contest once to see who could shoot the smallest diameter pile of empty cases after tuning several Garands'
ejector springs. He won."
n.b. Bart Bobbitt is a past Palma Team Member, and shot the Garand in competition for the Navy team when it was the primary service rifle for the USA (in addition to much other prior and subsequent experience).
He is a true expert, and has been there, done it and has a closet full of tee-shirts.
Anything he says related to shooting and related equipment is worth listening to, and carefully contemplating.