I agree that that out of spec magazine may be to blame and fortunately is a cheap and easy fix (get a new one (or better yet, new old GI Stock) of good quality). ProMags and Auto Ordinance magazines has a hit or miss reputation depending on what they go in and ditto for ex Korean military magazines.
Try Fulton Armory for quality mags and here is a FAQ from them regarding M1 Carbine mag markings
http://www.fulton-armory.com/\faqs\M1C-FAQs\Carbinemags.htm
Cannot vouch for this book as it is new to me on the M1 Carbine operation, history, and troubleshooting, by Scott Duff but appears to be useful from the descriptions from Brownells.com @ $20
http://www.brownells.com/rifle-part...s/the-m-1-carbine-owner-s-guide-prod5805.aspx
The book below is the gold standard on diagnosing and understanding how the M1 Carbine operates and how to fix it but it can be hard to read if you don't know some basic firearms and shop terminology. These are notes from Jerry Kuhnhausen's work as a gunsmith on these rifles during the golden age of milsurps.
THE U.S. .30 CALIBER GAS OPERATED CARBINES: A SHOP MANUAL @ $35 from brownells.com
http://www.brownells.com/gunsmith-t...-carbine-manual-sku924601001-25719-32963.aspx
Might be able to pick up these at Midwayusa or Amazon as well.
Hope this helps.
Try Fulton Armory for quality mags and here is a FAQ from them regarding M1 Carbine mag markings
http://www.fulton-armory.com/\faqs\M1C-FAQs\Carbinemags.htm
Cannot vouch for this book as it is new to me on the M1 Carbine operation, history, and troubleshooting, by Scott Duff but appears to be useful from the descriptions from Brownells.com @ $20
http://www.brownells.com/rifle-part...s/the-m-1-carbine-owner-s-guide-prod5805.aspx
The book below is the gold standard on diagnosing and understanding how the M1 Carbine operates and how to fix it but it can be hard to read if you don't know some basic firearms and shop terminology. These are notes from Jerry Kuhnhausen's work as a gunsmith on these rifles during the golden age of milsurps.
THE U.S. .30 CALIBER GAS OPERATED CARBINES: A SHOP MANUAL @ $35 from brownells.com
http://www.brownells.com/gunsmith-t...-carbine-manual-sku924601001-25719-32963.aspx
Might be able to pick up these at Midwayusa or Amazon as well.
Hope this helps.
