Had something similar last night,
My La7 against 109, at A2...headon merge, I dove underneath the 109 and turned to avoid the headon, 109 passed overhead, I pulled up to come up behind the 109 when I heard pings and my engine died. Never saw any flashes or tracers, and I know he had tracers because he came back and got me while I was ditching.
Also see some delay on my hits lately,...Fired on a P51 at about D200 with my La7, several hits and nothing, then wing falls off and he went down.