I have experienced it with cold/ clean and cold fouled bls in every calibre I have tested subsonic. The worst and i have to be careful; was a bolt action 300/221 with Sierra 240 gn MKs which was a very expensive disaster. I intend to do another as the case shows a lot of potential but something went wrong with the suppressor design and I suspect the bl profile was too light. I shoot 1000s of rounds on paper and through a chrony but the guys i talk to who hunt rave about them but have no groups to prove it.
The best theory i can offer is the hot gases contained in the suppressor which effect the velocity of the subsequent shot (up to 120 fps difference). I appreciate the loading info but this is with meticulous loading.
If I allow the suppressor/ bl to cool then lovely little groups appear. Can take up to 15 mins though unless I remove and purge the suppressor.
I went to a single shot akin to a T/C so that i could vent the gases quickly and blow though the opened action. This has significantly helped.
Info from the 300 subsonic semi shootes would be of huge interest.
|