This first shot from a semi goes into the blue?

[JAD]

The powder settles differently in the case. Depending on powder volume that will cause surprising differences in velocity (cf the SAAMI twist). I load 11 and dump the first round in the berm. Probably matters a lot more with .45 than 9 and in no way explains what the gun writer is saying.

[schüler]

Rifles with cold barrels it makes sense. In a handgun not so much.

Jacob Bynum has opined "cold bore" deviance is likely cold shooter skill.

Not to deny there have been some horrible barrels out there... but Jacob doesn't shoot crappy barrels for accuracy.

[Gio]

First shot deviation is a real phenomenon, but I wouldn't describe the first round as "in a different zip code." It's usually 1-3" away from the main group at 25 yds. Even official ransom rest testing recommends throwing the first shot away and then shooting your group. I think it's a combination of powder volume and the slide going into battery by hand vs. recoil.

[GJM]

First shot deviation is a real phenomenon, but I wouldn't describe the first round as "in a different zip code." It's usually 1-3" away from the main group at 25 yds. Even official ransom rest testing recommends throwing the first shot away and then shooting your group. I think it's a combination of powder volume and the slide going into battery by hand vs. recoil.

Mas Ayoob has discussed this for years. Some years back, when in a 100 yards with the Glock phase, I saw it in my groups and reported it here on PF.

Interestingly, I shot two five shot groups at 25 yards today, with AE 115, as part of getting a replacement DP Pro zeroed on a G5 34 MOS. With both groups, four shots went into an inch, and one shot was a little low and left, by an inch and a half. Will watch for this in future sessions.

[1slow]

Old target shooters used to mention this. More with rifle than pistol.

On a related note, serious revolver shooters used to # the chambers and see if one or more was off from the others. This can be minimized by line boring cylinders, like some of Hamilton Bowen's work.
Also read Seyfried's work on firelapping in revolvers, if the breech end of a barrel is the smallest diameter in the barrel the barrel will not shoot well. Lapping can fix this.

[Lester Polfus]

I've seen a noticeable difference between the first shot and the others in two handguns: a NIB Glock 20 Gen 3, and a NIB Springfield Mil-Spec. The Glock was a couple inches high at 15 yards, and it went away after a couple hundred rounds. The Mil Spec was less dramatic, and eventually went away, but at what stage of me replacing everything but the slide and frame, I don't remember.

[HTM]

I have noticed this with a M1 Garand, first round manually loaded on my M1 will usually go to about 11 0 clock, when aimed at bullseye, the rest go into bull, never noticed this with a pistol, however, but I suppose it's possible.. Might be interesting to test out with a ransom rest..

I've seen that. It's confounding to say the least. It's a real issue using the 2 round clips shooting competition.

[schüler]

I would think someone with a rest or other controlled test would have documented this. Will have to do some looking.

[GRV]

First shot deviation is a real phenomenon, but I wouldn't describe the first round as "in a different zip code." It's usually 1-3" away from the main group at 25 yds. Even official ransom rest testing recommends throwing the first shot away and then shooting your group. I think it's a combination of powder volume and the slide going into battery by hand vs. recoil.

It sounds like those two possibilities could be tested separately. Has anyone tested to see if allowing the action to load your last round at the end of practice has an effect on first round deviation at your next practice? This is what I do out of an abundance of caution, but I'm not a good enough shot nor have a ransom rest to test for a difference.

[Darth_Uno]

My first shot is usually dead on, and if people are watching I think "Oh crap I hope I can do it again" and fail catastrophically.