Bullet-Drop Reticles... FFP vs. SFP???

[jgcoastie]

What are the pros/cons of First Focal Plane reticles vs. Second Focal Plane reticles? Looking and reading online is starting to make my head hurt trying to understand what the real-world difference is...

Can someone shed some light?

 

[Regolith]

My understanding is that front focal plane reticles will increase in size along with the target as you increase power, which means it always subtends the same amount of the target area. This also means that POI stays the same with bullet drop compensation reticles.

With second focal plane reticles, the reticle stays the same size no matter what power you're using. However, if you're using a BDC reticle, it means that your point of impact for the BDC portion of the reticle will change depending on your magnification.

Here's a good example: with my Nikon Buckmasters 4.5-14x40mm SF scope, which has a second focal plane BDC reticle, the BDC markings (for 200, 300, 400 and 500 yards) will only be accurate at 14x. At 4.5x, it changes completely. I recently made a graphic to help me track the changes at 4.5x, 10x, and 14x using Hornady 165gr. SST .30-06 and the Nikon Spot-On program:

As you can see, at 4.5x, the center of the first circle marks 362 yards, where as at 14x, it marks 206 yards (the cross hair, which isn't shown, is zeroed at 100 yards).

If this were a front focal plane reticle, it wouldn't change from 4.5x to 14x. The first circle would always mark 206 yards.

 

[jgcoastie]

Regolith, thanks! I had more or less thought that's the way they worked, but I needed outside perspective to affirm it. Thanks for the info, seeing that diagram really cleared it up for me.