So I just picked up 2 new factory 14 inch contender pistol barrels. One is in 30-30 Winchester and the other 223 Remington. I?ll be mounting scopes on both. Does anybody here have input on what factory ammo or bullet weight either of these tend to prefer? Thanks in advance.

Check the twist rate on the 223. That'll be the biggest determining factor on what bullets it'll shoot well.

In several factory 14" .223 Contender barrels that I have owned, Black Hills .223 50 grain V-Max loads shot great.

The first Contender I ever owned was a used one with a 30-30 barrel and a .223 barrel. Never shot the .223, but the 30-30 was a true clover leaf shooter at 100 yards with plain old Corelokts. This was with a TC scope.

Federal .223 Tactical 55 grain works very well for me in my 12" barrel and did the same in the Super 14 when I had it.

John

my 14" 223 barrel shoots the Fiocchi 50gn Vmax load well (1" or less groups @100y) when I do my part (lots of practice with a focus on consistency). It's my go-to load in my rifle for p-dogs and varmints.

My factory 14" 223 liked 50 grain , most any brand. I did shoot mostly my reloads and they were 50 grain soft points , bulk DogTown bullets from midway. I did shoot a bunch of Black Hills after going to Wyoming and running out of ammo on Prairie Dog town shooting. Bought some at Sportsman Warehouse in Casper. They were 50 grn soft point and I didn't have to change my scope settings from reloads.
Good luck.
The 30-30 I had in a 14" shot the 125grn bullets mostly. Never tried 140 grain.
Took a couple of deer with Sierra Pro Hunter 125grn bullets and some Speer Hot Core 125 grn bullets.
Mike

Before I developed a handload for my 30-30 Contender, I used the Rem 150gr Core-Lokt. Never killed anything with it, but accuracy at 100 yards was 1 to 1 1/2 inches I believe and expansion testing at 100 yards was good as well. I think the Rem's would serve you well.

My 14 inch 30 30 contender loves 150 grain Winchester hollow points and they kill very well.

My 14 inch 44 mag contender loves Winchester 240 grain White Box soft points.

My 14 inch 223 contender loves Winchester 55 grain soft points.

federal 150's in the 30-30 worked well for me with groups near 1"