I just got my Whisper upper with 10" barrel, and have been researching scopes and reticles. The .300 Whisper is difficult because it drops so quickly at sub-sonic velocities. It does have a very linear drop curve, though.
The best theoretical solution I have found for a reticle is the new Leupold SPR (Special Purpose Reticle). This offers Mil-dot marks at 2.5 mil intervals all the way out to 15 mils (vs. 1 mil intervals out to 5 mils in a standard Mil Dot scope). This gives you 215" (18 feet!) of drop path in the reticle.
According to my Oehler Ballistic Explorer program, the 2 1/2 mil marks closely match the 50 yard drop points for Corbon 220gr sub-sonic, all the way out to 400 yards, when sighted in with a 90 yard zero (this puts you 2.5" high at 50 yards, and 1.5" low at 100 yards). You could also zero at 100 yards, but this add a few inches of error at longer ranges.
The only problem with this reticle is that it is available as standard on just 2 Leupold scopes - the Mark 4 1.5-5x20 PR and MR models. Leupold will add it to any Mark 4 or Vari-X III scope for about $200 in their custom shop.
The advantages of this SPR reticle from Leupold are (in theory):
+ 2.5 Mil-dot Aiming marks calibrate to within 2.5" for Corbon 220gr sub-sonic load out to 400 yards
+ Max 2.5" error at every range can probably be corrected to < 1" error by slight power selector adjustment
+ 15 mils of drop marks instead of the standard 5 mils (yields Whisper aiming points out to 400 yards)
+ Has excellent range estimating capabilities on man-sized targets
+ Illuminated Reticle is possible with Custom Shop add of this reticle to illuminated scope
+ Even with the custom shop add, it's an all-Leupold product with single-source lifetime warranty
+ Re-usable/re-sellable for standard rifle calibers (Leupold pitches the SPR reticle for use with .223 and .308)
+ Can recalculate drop tables and use the 2 1/2 mil marks with super-sonic/any .300 Whisper loads
The disadvantages are:
- Expensive, about $200 to add SPR reticle in Leupold custom shop (but competitive with Premier Reticles prices)
- Needs range testing to confirm drop calculations
- Doesn't really work as well as 1 mil dots for standard rifle calibers or super-sonic Whisper loads
I have bought a used Mark 4 1.5-5x20 PR scope on eBay in order to test out the drop points with this reticle, and will post results when available. If this works, my plan is to buy a VX-III 4.5-14x50 Illuminated scope (#54922), send it to the Leupold Custom Shop for installation of the SPR reticle, and re-sell the low-power scope on eBay. I don't think you need the Target Knob version since the reticle should give you all your drops, at least for 220gr sub-sonic. I hate those things, anyway, since I always forget to reset them.
Here's the scope I bought used ($360) for testing:
http://www.leupold.com/products/tact...-5x20mm_PR.htm
And, here's the SPR reticle:
http://www.leupold.com/products/tact...ticles_SPR.htm
One last thought - the .300 Whisper 220gr sub-sonic at 400 yards still has more energy than a 45 acp at point blank range. I like to shoot gongs and varmints at long ranges. Even though 300 yards is usually considered the max, I believe that with a laser range finder, the right scope and a 1MOA rifle, you can make consistent hits in a 8" circle at 400 yards.
I apologize for the extended "Scope Nerd" discussion above, but thought some of you might find this useful.