Is there anyone in here who has an FX Crown? I have a Crown Continuum .25 cal and I have done the port, probe and hammer. I have ordered but not yet received a 6.35mm valve seat. I am wondering how much improvement stands to be gained by going from the 5.5 to 6.35 in .25 cal? I have brought my FPE from 55 to 69 so far (at 160 bar), and I am hoping to hit 80 FPE...if I can keep the reg in the same place that would be good because I will not need to replace the spring washers for stiffer ones.
What do folks reckon are my chances of hitting 80 FPE by replacing the last airflow constraint that remains in my system?
FWIW the 5.5mm supports porting up to 4.32mm and the 6.35mm supports up to 5.35mm porting...the power difference between the two (depending on caliber and a few other variables) is roughly 15% so it is possible, provided you port upwards of 5.35mm forward of the new 6.35mm valve seat...
This is provided the stem in throat is 3.175mm...if you reduce the stem od in the throat area, one can achieve the same effect, its quite safe to go thin down the stem to 1.9mm (only in the area the stem resides in the throat at rest and while at max lift), doing so allows one to run the 5.5mm seat with up to 5mm ports without requiring more hammer to open the valve...or you can run a thinned stem, and 6.35mm seat and run porting upwards of 5.85mm, which would provide a lot of benefit..but you'd have to make sure the probe area isn't restrictive running ports this large. HTH
Porting beyond 85% or so of caliber takes a lot of care to not go too wide on the barrel port so that pellet damage occurs upon loading, most run oval ports when going beyond 85% of their bore OD.
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