That is Marko from Finland. He has made over 3000 fpe with that gun. He is shooting 158 grams/2438 gr.
Is he the same guy that posted that original fpe years ago on an extinct forum? If I remember back then that fellow used a 600 grain monolithic turned slug & a dump valve. He stated it was less than pleasant to shoot & only did it to see if he could. He wasn’t out to set any records when he beat an 06 in muzzle energy & probably terminal to a short distance with a PCP.
If that’s the same guy he came a long way. I haven’t watched videos yet, and I’ll see if I can track down old post. I’m very curious scientifically, not like I want one, because I don’t. I’m curious if they’re the same guy. If Helium is used in either one. At what point did he decide a controlled valve & longer barrel worked better than a dump valve. You know 1st hand very well what a “measly” 1200psi can do with a .22 slug & the right length barrel. I really wish more production guns came (at additional cost of course) with optional barrel length up to 36” on .177’s-.25’s. Seems AF is only one not afraid to put a 36” barrel on a long rifle. Short bull-pups, sidelever, big multi shot mags being the in thing.
IDK. I guess short has been preferable for a long time as most guys cut their Brown Bess down to 2 barrel bands or shorter instead of production 3 band length.