All the things mentioned here can be part of the problem. If the difference is 10" then it is most likely a combination of 2 or 3 problems.
First- Make sure you have a good quality arrow and that they are straight (Poorly made arrows will never fly just right, no matter what you do to your bow).
Second- Make sure your Broadhead is straight with the shaft. Do this by rolling the arrow on an arrow straightner, a spin tester or on a flat surface. If the B/H wobbles up and down, try a different arrow shaft. If none of your arrows will spin any of your B/H without movement, you need new arrows.
Third- Don't worry about aligning the blades with the fletches. 3 blade, 4 blade doesn't matter. Make sure you Broadheads and field points weigh the same. Check them if you can. Not all broadheads or field points are equal in quality.
Fourth- Tune your bow. Paper tune, walkback tune, eyeball it. Whatever works for you. Then shoot B/H's and field points to get them to hit at the same point at 20 yards. Adjust your rest, whether it is center shot adjusted or nock height adjusted. BRING THE BROADHEAD TIPPED ARROWS TO THE FIELD TIPPED ARROWS (i.e. if the B/H arrows are hitting to the left of the field tip arrows move the rest to the right. If B/H are hitting high, lower the rest, or raise the nocking point).
Fifth- Repeat at further distances until you run out of sight pins or get tired of fooling with it. Remember the longer the shot distance the smaller the adjustments.
Sixth- If your bow just won't tune. Check for your arrow striking your rest, cable, riser, etc.
Seventh- If none of these work. You know the arrows are properly spined (by the manufacturers charts, not "my buddy shoots these arrows, so I know they are good"). It may be time for new arrows, bow checkup or most likely a shooting lesson (most bows that won't tune, with all the properly fitted equipment, is usually a shooter problem). I know everyone thinks they can shoot Coke can sized groups at 80 or 90 yards. But, this is just the fact. Most incurable bow tuning problems are a problem with the shooter and not the bow. Bad bows do occur. But not nearly as often as bad shooting.
Now I am not pointing fingers at anyone specifically. I'm just noting what I have found in the last 25-30 years of doing this.
If you get close but still not perfect (say within 2-3 inches). You can just resight for Broadheads. That will work. But, one word of caution. Set your sights for broadheads. If you are thinking "I will just compensate for the difference on a deer". You are setting yourself up for heartache. Make your your setup foolproof by making it so you don't have to think about anything extra, at the moment of truth. Because, in the excitement you will forget.
