great ideas all.
I guess you could also try to find a cheap load with same POI as your htl loads.
I have a saddle mount i used to remove on my sons 870 20 gauge.
Re sighted with low brass dove and quail load at 15 yards.
And ended up with a 2 3/4" Federal Premium Pheasant 4 shot that patterned same center as 3" HEVI 13 TURKEY LOADS AT 25 TO 40 YARDS. Heck maybe just lucky, but worked in this case. Always shot a hevi 13 at 30 though to triple check, but hated wasting one of those loads.