I have shot 3 gun and USPSA since 2009. I recently wanted to get into DMR matches. I shot my first DMR at K&M last weekend. I took my 16" 5.56 3 gun AR with a Vortex PST 1-6 Gen 2. I had the weakest scope at the match. There were static targets 300-520 yards with many of the 520 yard targets being 12" plates and moving targets at 150 and 300.

I did ok, I had a lot of hits, hit all the movers, but it was hard making out the long shot coyote and bobcat steel targets, reading wind and seeing misses with a 1-6x. I was much slower than the better glass.

I am building a DMR 5.56 DMR rifle. My 3 gun AR is for tac ops division (no bipod), minimalist, very light weight and set up for close paper to 500 yard full silhouettes. In DMR there is less movement and less swinging of the rifle side to side, I can afford and I need more weight. So the DRM rifle will have a better stock, 2 stage trigger, forearm with a rail and bipod.

Which scope? I think FFP will be nice for scaling at any distance. Finding targets at max mag is difficult when ranging with a SFP.

Budget: $900

Weaver 3-15x50 SFP mil, $450+/-
SWFA 3-15x42 FFP mil, on sale now for $500. I am leaning to this one. Talk me to it or away from it.
Weaver 3-15x50 FFP mil, $800+/-
Vortex 3-15x44 FFP mil, $900+
Other?

Sig has quite a few scopes in that price range. LINK

I was going so say March 3-24x42 until I saw your tight budget....used Sig Tango6 3-18x is the ticket, or maybe one of the FFP Athlon's.

I had the SWFA SS HD 3-15x on a 6.5C bolt gun. Seeing a 4" plate at 500 yards and hitting it all day long was zero problem at 15x.

Never competed so cant really help you there but I'd be between the SWFA and Vortex. The price on that SWFA is pretty great.

I really like my gen1 Tango 6  3-18
Got it on clearance on DVOR (optics planet) for ~600 about a year ago.

I have a similar list that includes the following:
- Athlon Ares BTR 2.5-15x w/APLR3 MIL reticle $900
- Primary Arms 3-18x w/ Athena/GRID-2B reticle $500
- Sightmark LR2 3-18x w/ LR2 reticle $600
- Atibal 1-10x $800 (pre-order $650)

I'm kind of on the fence with 1x vs 3x on the bottom end for a DMR role. I like the flexibility of the 1-10x being capable of 0-1,000 yards but for accuracy or longer distances the 3-18x or 3-15x would be much better.

Bushnell ERS or one of the HDMRii......3-21 magnification and short overall length. Not to mention they are extremely solid and durable.

If you haven’t looked at Burris XTR II scopes in this range, they are great

I’d personally opt for a 2.5-10x with a 5.56 rifle

Burris XTR II 2-10

ETA: the 3-15 FFP mil/mil is under your budget at sport optics

IMO you are on the right track. I finished 3rd in the DMR match Jason had back in July with a SWFA 3-15 on my SPR build. I think SWFA's scopes are possibly some of the most underrated scopes out there. I shoot nice glass on my PRS rifles and still love the SWFA SS scopes. There's a guy on the Hide that makes zero shim kits for them that really helps out as well.

Another option is the SWFA 3-9x42 HD, I snagged one of these on Black Friday and just got it mounted this weekend and its really nice too. I think it is going to be my DMR match optic for '19 since it's just out to 600yds.