.22 Bolt.

[tr63]

If the poster will measure the bolt head it would help a great deal as to what it goes to. The No. 7 is 2 3/16'' in length more or less the No.8 1s 1 3/8'' more or less . It looks like there is a left side extractor which is retained with a screw . The No. 8 doesn't use 2 extractors and there is no slot cut for the second extractor .