All of my shooting has been done with the bayonet off.  I'm wondering if anybody knows from personal experience how much, if any, the point of impact changes when the bayonet is mounted.  Please include the length of the barrel you used, the barrel's profile, and whether you were using the M7 bayonet (which weighs 9.6 oz) or the M9 bayonet (which weighs 24 oz).

this is a weird question.  if you want to shoot past 100 yds take the bayonet off.  the bayonet should not even be on the weapon if the target is farther than about 50 yds.  it's a 1/2 LB hunk of steel hanging off the end of your rifle.  of coerce it will affect the bullets.

You have a rifle with a bayonet lug and it's a preban take it to the range and shoot it to see what it will do.  don't rely on us to tell you what works with our guns.  the info is worthless to you because your gun may react differently than some of ours.  

to answer your question a bayonet will not affect the flight of the bullet at bayonet fighting range.