From page 1004 (of my Kindle version) of “Reclaiming History” by Vincent Bugliosi:
One evening at the end of August Marina returned from a twilight stroll with June and found Lee on their screened-in side porch, kneeling on one knee, aiming his rifle into the street and working the bolt—dry firing. 1365.
Footnote 1365. 1 H 21–22, WCT Marina N. Oswald; McMillan, Marina and Lee, pp.451–452; CE 1154, 22 H 190.
This is why you should always check primary sources. 22H190 says nothing about Oswald doing this. And Marina’s testimony says nothing about dry firing.
Mrs. OSWALD. No. I know for sure that he didn't. But I know that we had a kind of a porch with a---screened-in porch, and I know that sometimes evenings after dark he would sit there with his rifle. I don't know what he did with it. I came there by chance once and saw him just sitting there with his rifle. I thought he is merely sitting there and resting. Of course I didn't like these kind of little jokes.
. . .
Mr. RANKIN. You have described your husband's practicing on the hack porch at New Orleans with the telescopic scope and the rifle, saying he did that very regularly there.
Did you ever see him working the bolt, that action that opens the rifle, where you can put a shell in and push it back- during those times?
Mrs. OSWALD. I did not see it, because it was dark, and I would be in the room at that time.
But I did hear the noise from it from time to time not often.