On most HS guns, you should shoot only std. vel. ammo. Even on some that can take it, why beat up an old gun with HV ammo? It's almost always less accurate as well.
Second, HV ammo will almost always shoot higher than SV ammo, espcially in a pistol, due to muzzle rise present with more recoil--and also due to less bullet drop at longer ranges.
I strongly suggest you switch to SV ammo, should cure your high and low problems and maybe your windage problem too--sometimes different ammo's shoot to different point of impact, vertical and horizontal.
I am partial to CCI Std. Vel. ammo due to price, no duds, burns clean, reasonably accurate. Another good choice is Fed. 711b if you cant find CCI SV around. Rem. Target is reasonalby accurate in my guns, but burns dirty and lots of duds.
Hello all, this is my first post. I’m not knowledgeable about High Standards and their evolution, so this website is the cat’s meow for me… thank you! 47 years ago when I was 16 years old, I worked... more
Duramatic shoots high — Steve Stafford,Fri Jun 8 10:08
Just realized you mentioned center hold. Most HS guns, at least the target guns, were designed for a 6 O'Clock hold on a paper bullseye. But I am not sure about the Duramatic's and did not see a... more
Sorry, I should research more before I type! John DOES list a manual for your gun, here, for Plinkers and Duramatic's http://www.histandard.info/manuals/dura/0274D150R.pdf Duramatic's too are... more