Making Changes To Your Rifle That Can Shift The Point Of Impact
Sometimes a POI shift is simply due to a parts change, usually toward the front of a rifle. Changing muzzle devices always requires a re-zero, but even removing and reinstalling the same flash hider or brake can shift POI. Changing a semi-automatic’s gas block or a barrel nut to support a different handguard will also affect shot placement on target. Any alteration of things that touch a barrel, especially in terms of their position, weight or pressure, will alter point-of-impact. So long as the parts change is intentional and everything is mounted and torqued securely, a simple re-zero is all that is required to deal with this shift.
Items that attach to rifle fore-ends are the root cause for most problems I see. The typical offenders are the screw ends for M-Lok, KeyMod and backer-plate accessories. At least one company includes screws that are about twice as long as needed to secure its M-Lok accessories. Thus, it is very easy to wind up impinging on a barrel or gas block, resulting in POI shifts and accuracy-related problems. The heavy-barrel contours typical of chamber areas increase the chances of this problem as you move rearward along a handguard.
I said the same thing about the affect of attaching lights directly to the barrel four years ago, and was [incorrectly] torched in the comments.
But I was right then and this author is right now. I didn’t make it up four years ago, and this author isn’t making it up now. Machine harmonics matters.
I would add that not only can you make changes to your rifle that affect the POI, you can make them in a way that yields reduced accuracy even if you re-zero the gun (due to additional harmonics introduced by the component, making for an unstable system). So this would mean larger groups.
I love floated barrels, and I don’t attach anything to them. And as all hunters know, if you have a wood stock and it gets wet during a rain, if the wood swells and you can’t take that piece of paper and slide between the stock and barrel (you know what I’m talking about), your zero is off.

