I've recently installed a Timney Featherweight in a Mauser 98.

I'm having troubles where when the bolt is cammed down and the trigger pulled, the sear won't drop away from the cocking piece.

I've switched out the trigger for a Timney Sportsman and everything works just fine. So I know the gun is ok.

Could it be something with the shape of the sear? The Featherweight is slightly squared in the front and the Sportsman is rounded in the front.
Or could it maybe be to do with sear height and engaging too early?

The sear may be binding on the action. If so the hole in the action needs to be opened up a little.

The sear moves freely without the bolt installed.

The sear needs clearance when installed. If the sear isn't binding on the hole in the receiver, then the sear is too high. Timney makes a lower sear or shim between the trigger housing and the receiver. It doesn't really matter if you shim the rear or the front.

ETA: I have had the same issue with Fwt Timneys, many times. I can't ever recall that problem with a Sportsman either.

and it WORKS!! Thanks airgun1!! I placed a shim on the rear of the trigger and the sear clears the bolt and the cocking piece moves forward.

Thanks again.