Bench test it, then if tight/accurate groups..
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Is this your first 40cal..? Same question about your friend, first time with a 40cal.. a/o 357sig ?
Both of you are right handed shooters.. is my bet
Low is the anticipation of the recoil just as you pull the shot.. (that is why they are going low)
Left is the quick trigger pull/s as you get the sights on target, you quickly take- the-shot (NOW!!! - rush shots) and you're jerking each shot, that is why they go left..
Same with your friend.. is my bet.
40cals, much like 357sig, need some time to get the right feel for, being relaxed and letting it happen, as the Sig P229 is very balanced and falls, naturally, back on target for nice follow-up quick groupings.. Once you get comfy with it, and the light comes on, so to speak, you'll appreciate how they are really soft shooting 40cals..
Bench test it, as mentioned, in SA format and you should get your answer, along with, take a few 40cal snap caps and insert them randomly into your live ammo per mag.. My bet is when you think it's gonna go bang and it doesn't, just clicks, when you get to each snap cap, you'll see your gun dipping down, quite a lot.. (even better test results if you let someone else load them so, you can't count.. LOL) but even if you do load them, your brain will think each shot is gonna be live..
Have 3 40cals, 2 in P229 and one in Beretta Px4 and Sigs 3 dot night sights on one, 2-dot combat sights on the other Sig, both require sights, at close range to be just halfway on target or just below, with 165gr, and with 180gr they need to be at the bottom of POA-POI, especially from 25ft out..
Also, if your using the factory plastic grips, you might want to invest about 24 bucks for some Hogue rubber, side-panel-only, grips.. They're wonderful with the P229.. Have them on both mine.. makes for great comfy (non-changing) grip and absorb some of the "felt" recoil.. smoothing things out nicely
OMMV,
Ls