[Unclenick]

Originally Posted by ops

OK you said "Group size at 25 yards with any of my[your] .45's is identical regardless of the cartridge OAL."

I never said any such thing, so the quote marks are not appropriate. That group was intended as an example of a load which was not tuned to the gun in any particular way. The gun is, however, a tightly match accurized gun and not typical.

That would have been good enough. I get most of my groups from the range, and most of my sermons from Baptist preachers.

I was not giving you a sermon. I simply pointed out your blanket statement that nobody pays attention to seating depth is a false assertion. And also, you will confuse readers if you try to use cartridge length and seating depth interchangeably. Since we have many dozens more readers of each thread than ever log in to read or participate in them directly, defining terms to keep communication clear for them is a normal moderating role.

I find that 0.010" change in seating depth with 5.0gr Win.231 and a Berry's 230RN in a Kimber Stainless Target at 18 feet from a sandbag puts 10 rounds in 7/10". Any seating depth other than that specific COAL value throws them all over a 12x12 paper. I wonder if anyone ELSE sees this type behavior.

And the thing is, when I ask a ballistician they say it shouldn't make a difference. OK! And the guys that got me into the ACP shooting can ding a quarter at 25 yards and they say they've never even thought about seating depth, as long as they get proper feed and function!

OK. Now I understand what you are asking.

The most likely cause of that much group spread is the action not locking up consistently completely. It can be consistent enough to fire and function, but not enough to get the barrel into the exact same position relative to the sights each time. That can happen if the rounds don't chamber smoothly enough and some guns can be very, very picky about the exact cartridge length when it comes to feeding a particular bullet. I suspect that's what is happening here.

When you have some of your ammo that goes all over the map, try loading just one round into the magazine at a time and dropping the slide manually to chamber each round. Then push on the back end of the slide to ensure it is all the way in battery. See if a group fired with these singly-loaded rounds is tighter. If so, then you have the answer; it's a feed problem with the other cartridge lengths. In that case, having a reputable gunsmith do reliability work that includes feed ramp and barrel alignment and timing on the gun will likely remove much of that sensitivity.