Viking - while I know nothing about Howas, I too have a .243 that I got in the late '80s. This is a Remington 700 that was virtually new with less than one box of ammo put through it and THAT may have been the reason it was sold.
I started testing the rifle with Remington, Federal, and Winchester factory 100 gr. PSPs at a range with 200 yd. set-ups as I wanted a 200 yd. zero in the 3-9x scope on the gun. The blasted ammo was all over the paper !! I would shoot 5 rds. of each ammo with a swabbed barrel between groups, but nothing seemed to help. So I started reloading.
After a fair amount of research (and letter writing), I settled on Accurate 2230 for my powder as it can be used on all three bullet weights I'm shooting. They are Sierra 60 & 75 gr. HPs and the 100 gr. spitzer boattail (SPBT). For safety reasons, I started assembling rounds at 2-2.5 gr. below MAX and with all three, my best accuracy was within 0.5 gr. of MAX. With the 60 gr. bullets, that was 37.8 gr. (38 is MAX) and the 100 gr. is at 33.3 gr. (33.5 is MAX). One variable I failed to consider was the BRASS as I was using fired brass from Rem.-Peters, Savage-Stevens, Federal, & Winchester and that can alter the internal pressure. Despite that, shooting one round at a time (on sandbags) at 200 yds., I put 7 shots on paper with 6 in an arc that was 1.25" wide by 2.25" high with the 7th shot about 1" further to the right.
Depending on how new that Howa is, it MAY just need to be "shot in" a bit to help smooth any imperfections in the barrel.
I do NOT know what the twist rate of either the Howa you are considering NOR of my 700 but I know the ammo I have made works.
p.s. - 2230 powder is no longer listed in the manufacturer's manuals as it is a "semi-sperical flattened ball powder" originally designed for the .223 and is a fairly fast-burning powder. It WILL cause more "throat erosion" at the chamber end of the barrel because it burns a little hotter but I have about 500 rds. of those three bullet weights already made up and don't want to mess with the scope and retest the ammo. And that range was destroyed in the great St. Louis "Flood of '93" and I no longer have access to a range with 200 yd. set-ups.
Good luck with your choice !