I'm currently doing an SPR-esque build with an 18" HBAR from Criterion. Intended engagement range is 300-800m, with shots out to 1000m when bench resting for fun.

I'm planning on a FFP 3-15x scope since the weight difference between that and a 2-10/12x is negligeable.

For these relatively shorter engagements at lower mag ranges against multiple targets, should I opt for a mildot type reticle like the SCR, or the Horus? Never used a Horus type reticle but heard good things about it.

I find something like a Horus, xmas tree, ebr-2c, etc... to be about optimal.  JMHO.

my two cents

I got into longer range shooting with standard mil-dot.  in the middle of a long range class, my elevation turret broke, so the instructor was kind enough to let me use his Bushnell HDMR II 3.5-21X with H59.  I have never looked back after using it.  I was going from estimating b/t 1MIL dots to something that had holdover lines.  I could use the bottom grid out to about 600M for wind calls and elevation - no dialing.  (I was shooting 6.5G on a course that had 600 - 1000Y, from memory, 1K is a 13 MIL elevation dial/hold).  Yes, you can do all of this on a standard mil-dot, but the extra granularity and bottom grid are REALLY useful.  If you are using a round like 308 or 6.5C (everyone else was), you would never have to dial out to 1K.  I think 308 elevation holds were in the sub-10 range and 6.5C were in the mid-8's.

The elevation lead lines (those right on top of the horizontal stadia line that make a "hat" across the reticle) can be used to do distance/hold estimation without formulas or range finder.  We tested that out as well and it works well enough to make hits.

If I could do it over, the two scopes I have that are mil-dot would be H59's or Tremor3, or the Vortex EBR-2C.

That being said, there is absolutely nothing wrong with mil-dot...especially if you are just learning the ropes with it.  That's my two cents from an average long range shooter that does not do competitions, etc, etc.

I have a Vortex with the EBR-2C mrad reticle.  I like it.  Eliminates the need to dial in many circumstances.  Lack of windage holds is a deal breaker for me for shooting longer range, personally.    You COULD always dial but IMHO the reticle has great utility.  If you manage to spot your miss you have a useful reference point as well.

This. or the SKMR3

I have a Horus H102 illuminated and LOVE it! I was looking at a Steiner with the MSR reticle, but after shooting a friend's rifle, I'm glad I saved up a little more for the Horus.

If you like the Horus, go for it.  There are lots of people that do.

I tried out ATACR 4-16s with the Tremor3 and the Mil-C.  With the T3, the reticle got very small at lower magnifications and became harder to use. The Mil-C, while small, was still very usable.

Though I can see the usefulness of the Horus, I don't find myself wishing for one unless I'm trying to 1) shoot really fast 2) in lots of wind 3) past 600 yards.