Rifle is built with a MRC stainless action in 35 Whelen using new Remington 35 Whelen brass and CCI primers. Finally went to the range today to test fire it and the firing pin is hitting the primer so light it is barely making a dent.
Where to look first?

Did contact MRC and Jeff said to send it in but with the cost of shipping being what it is today would like to have the obvious checked out first locally before shipping the rifle out.

I had a similar problem with a Mannlicher Schoenauer .30-06 and the problem was crud in the bolt. You might try a qick cleaning and flushing of the bolt to make sure it is not filled with old grease.

Action is new and bolt is clean.

My first thought was "headspace is too long", i.e. chamber's too deep, or the rounds are too short.

To check the firing pin protrusion, pull the bolt and let the striker down, the firing pin tip should protrude from the bolt face .055"-.065".

I'll have the smith who installed the barrel and trued the action to check the headspace and firing pin protrusion before proceeding. Hopefully it will be one or the other.
Anything else?

Snowwolfe,contact Wolff gunsprings and tell them about your issue.They may have a replacement or heavier spring for you.You may need to supply measurements of your spring-overall lenght,coils per inch,wire diameter...

MRC uses Wolff springs so the spring should be
fine.The pin screws into the cocking piece.
The cocking piece is always in the same spot
when it is forward position against stop.
Have your smith screw it out a little so
that its protrusion is about .060" when the
pin ii forward in the bolt.You have to check
them with bolt out of gun and the cocking
piece turned onto cocking notch in the back of
the bolt, if no smith handy I can do it ok,
as I had to rework MRC PH pin to fire
BMG primers.I set it at .085".ED

I don't know if this is pertinent or not but I gave my Tikka T3 300WSM to my son and he replaced the scope mounts on it and then complained about mis-fires because of light FP strikes and he found that the bolt wasn't closing fully because he had put the mount screws in the wrong holes and the bolt was hanging up on one of them. You may need to look at something like this.

I am beginning to think it is no fault of the action, headspace or the way it was put together.
The shoulder on the unfired Remington brass looks very small and very "rounded" to my untrained eyes. If my hunch is right when the firing pin strikes the primer the shoulder is so small it is permitting the case to move forward absorbing some of the firing pin striking pressue.
I plan on pulling the bullets and reseating them just a tad long so they will engage the rifling. Then the case cant slide forward. Once they are fireformed everything should be ok if my hunch is right.
Will try it tomorrow and tell you what happened as well as tell the forum it was not a fault of the action if it works.
I did have the smith check the headspace (fine) as well as the firepin protrusion (fine as well).

.35 Whelen case gage
This gauge will eliminate any guesses about the ammunition.

While it may sound a little "silly" for lower 48 occupied US... Have you thought of firing with the muzzle up and placing the weight of the loaded cartridge on the boltface?

Of course use all caution as to what may be down range, but hopefully there is still some unoccupied space in Alaska...

Went out yesterday with once fired brass neck sized only and fired off 20 rounds with zero misfires.
Can only conclude the issue was 100% caused by undersized brass and not the fault of the MRC action.