I have the same rifle. I actually had no problem shooting BlackHorn 209 with the orange primer jacket. But have your friend check the face of the breech plug and he will discover that the blow back is eating the face of the breech plug very badly. eventually the powder will totally block the breech plug fire channel. And the face of the plug will still produce the blow back which BlackHorn is supposed to eliminate.

What I did was with the help of Sabotloader.. went to a Knight Disc Extreme bolt and the Lehigh/Knight Breech plug for shooting black horn. I then had problems with the W209 primers as they were not hot enough. But I switched to the CCI and the Remington STS primers and now can shoot blackhorn with no problems.

I would recommend to your friend if he is serious about wanting to go through all the bother and shoot BlackHorn 209 to make the conversion to the Lehigh plug and the updated bolt. Personally if I had to do it all over again, I might still make the conversion but would probably be shooting Triple Seven 2f powder as I get extremely accurate loads with it. Or Black Powder. And all of that can be done with the orange primer jacket, the old breech plug, and the same bolt as before.