Typically the “standard” separation for loft for off-the-rack clubs between the 3, 4, and 5 irons is 3 degrees; between the 5, 6, 7, 8, 9, and PW it is 4 degrees.
Golf club foundries usually promise +or-1 degree of tolerance. So, for arguments sake, let’s say that the 3 iron had 22 degrees loft instead of 21 degrees, and the 4 iron was 23 degrees instead of 24, which would result in only 1 degree of separation between the clubs. Now if you swing at 80 mph and hit the sweet spot every time you will only have about a 2 yard differential between the clubs. Oh yeah, the foundries don’t always hit their “guaranteed” tolerances. I once checked a big name set of irons and discovered the 7 and 8 had identical lofts.
Unless your clubs were assembled or adjusted by a reputable club-maker you owe it to yourself to have the lofts checked and adjusted if necessary.
Cost of this service is only $5.00 per club.