Long time lurker.
Im new to Thompsons and recently picked up a Thompson M1 bolt from Apex when they had a couple for sale.
When my bolt arrived it had lightening cuts in it. I have never seen this before and cant seem to get any info on it.
My only real guess it was done to UP the cycle rate or maybe for sand. I know FN added lightening cuts to FAL bolts so they would operate better in desert environments.
Anyone have an idea what this is?