I may have seen a post similar to this but cant find it. Any reccomendations for a Williams receiver sight in a FD or 5P?
Thanks.

I've always used the Williams 5-D receiver sight with a .125-inch diameter aperture. I've always left the factory Marlin bead front sight in place. Excellent set-up for me for a lot of years.

Hunh. I just put a 5D on my 336 and I couldn't get it zeroed with the factory bead. Shot too high. I had to put a taller bead on (.450 height) to get the 5D to work on my 336.

They both work just fine. I have both on Marlins. If you use multiple loads in your 30-30 the Foolproof will be easier to adjust from load to load because it has micrometer/click adjustments.

The 5D works great for the one-load per gun approach. Once it is sighted in you are good to go. But frequent re-sighting for different loads is a hassle as it has no micrometer-type feature. It takes a little more cut and try to get your zero. At times this can eat up a fair amount of ammo just getting zeroed.

With either one you MIGHT need a different height front sight.