Can't cast anymore as I'm legally blind. Is it OK to use Saeco's 170 gr. taper bullet used for breech seating in a fixed round. Will only be using it to plink with. Thanks, Dale.

You just have to make sure you can hold the bullet in the case without it slipping down onto the powder.

I've used my old Hudson mold cast bullets for my .38-55 in my Schoyen barreled Ballard as fixed cased cartridges often, and they shoot extremely well. The barrel is actually a false muzzle setup, and I had low expectations shooting fixed, especially with a stepped bullet. But it's proven to work well with groups around 1.5" at 200 yds. off the bench.
I also use a Saeco mold for my .32-40 that has the base band opened up for a better seal in my Hepburn Match B and I shoot it mostly breech seated, but it shoots almost as well fixed also.
Since both are single shots I never worried about or even considered a crimp, and no issues with bullets staying as seated.

On my Dillon 550  loading for BP or smokeless.I had one gun after shooting that needed the FL die to just size  case enough for the flair station to just open up enough for the  seating station to seat to proper length .Last station a taper crimp die to smooth it out and hold bullet....
Setting up my German Schuetzen to shoot fixed,we shall see.....