Martin is correct.. The answer can be found in the older Lyman reloading book..Look at drop at 20/30/40/50 yards.. and you'll also see The larger shot drops less at long ranges. For long range shooting.. speed is your friend.. but 50 fps at the muzzle will make 8's perform like 7.5's..
At short range slower loads have a higher POI. This is because of the launch angle. When the shell is fired the muzzle starts to rise, a slow moving projectile takes longer to travel down the barrel and is launched at a higher angle. HMB
Well while we are on this, I just took my Super X1 out Thursday. It has a brand new IM fixed 30" barrel. Anyways from the 16 it was ink dotting targets or I was missing completely, I was shooting a full 3 dram 1 1/8 load, so am I correct in thinking that if I drop down to 2 3/4 dram the load will be slower giving the pattern time to open up?
If you look at the data published by Lyman.. the differences are fractions of an inch till you get to long yardage..so what Neil stated would appear correct. Math however would prove the statement not totally accurate.. Kind of like the Red Dot/Green Dot recoil perception.. On the other hand.. My biggest problem is I can't shoot slow shells at long ranges.. I too think they shoot to very similar POI.. but a slow shell goes pull..................break.. and a fast shell goes pull..break. Yes.. I know the math says is .005 of a second difference.. But my mental computer DOES see that. Big time.. From the 27..my bottom speed is about 1240/1250 fps.. Any slower and it all goes bad very quickly for me.. In a blind shell test I was 92% with fast shells.. and 68% with slow shells.. not knowing what was in my shotgun at the time.. It might only be me.. BUT.. it is me and I must learn from that.. All Good.. Mike
I can second what ParazziBB is saying about the perception of slower shells in handicap. The math doesn't support the feedback, but for me I get about 5-6 shots per hundred that the thought I missed flashes through my head then the target breaks. I always thought a person doesn't really "see" whats going on as the gun discharges but maybe the recovery time is the differance between shooters.(?) Dan
Home spun theories aside. Poi can change; in fact it changes from shell to shell of the same load. Harmonics long recognized in rifle shooting can play a similar role in shotguns. Some loads seem to hit the same place; others won't group and others move the group. Shoot all shells you intend on using. This is the reason most top shooters shoot only two or three different loads. ( you won't see a top competitor testing a new favorite pet hand load every week)