So far, me,... I am pleased with the results with good aftermarket parts. This kind of work appeals to me, numbers are my thing.
In all fairness, with all of the very good replacement and upgrade parts, you can get phenomenal results with the right combination.
Marauder .25 caliber setup on the airgun:
Hill flyweight Aluminum hammer, with lighter than factory striker.
Hammer tube deburred and polished, with graphite lube.
TSS Hammer spring system, using the two lightest springs in the set, set close to minimum settings.
Huma regulator with integral gauge block, set to 1800 PSI.
Hill valve with optional lighter spring.
Increased port to 0.187 with interior of bore radiused at port, with Hill 0.187 plastic transfer port tube.
Reshaped bolt to enhance flow where it would normally partially block the transfer port.
42 shots at 40 FPE with JSB Exact king 25.39 grain (unsorted) with a maximum variation across the entire shot string of 1.8 percent (fastest shot to slowest shot variation).
Soon, I will be increasing the Huma regulated pressure up to about 2100 PSI for the heavier JSB Exact King Heavy 33.95 grain Mark II pellets. Goal is as many shots possible with less than 2 percent variation at 50 FPE.