In a few weeks I will participate in my second match, which is 300 yds again. Did ok the first time (581) using my Weaver 4-20 x 50 on the Savage 223; assessing areas for improvement I had issues resolving the x ring as the day progressed. Had a booster lens attached to get around 25X, and I think this also helps quite a bit to reduce parallax. So for a couple of days I have tried my Weaver T36, and today even at 75 degrees the mirage was terrible and I was unable to achieve a steady image of the bulls-eye. Parallax seems worse with this scope too, even dialing various settings. So it looks like I will go back to the 4-20 to combat mirage, and investigate a new scope for the future. Right now I'm considering a Sightron 10-50 1/8MOA, and will research this a bit more. Besides a new scope, any other tricks to consider?
The clearer the glass the longer you have before mirage begins to be an issue. The booster lens, while adding magnification adds more pieces of glass to create distortion.
I shoot Schmidt Bender PMII 12-50 scopes. They do a good job of seeing through the mirage, but come with a price. And I usually stay around 50X.
The NF 12-42 BR is an excellent scope. I had the CH3 reticle on the one I had. I also had the NF 8-32 and it also was very good. I just decided to upgrade another step. If you watch you can probably find one of the 12-42's on here or Accurate Shooter selling for around $1000. An 8-32 may run a little less. I recommend going with MOA also, as was stated earlier you can fine tune it better.
A good, solid bipod is a must. I don't know what you are currently using, but a Sinclair Gen III, Sinclair Tactical, Atlas along with some others are very good. But they will set you back around $250 or more.
A good back bag is also essential. Again, don't know what you have, but Protektor, for one has a variety of back bags. Some with high ears, some with low.
A good shooting mat will help make it more comfortable in the prone position. There's nothing worse than being in position with that rock under your thin mat grinding into your leg.
A spotting scope is useful, but not really needed at 300. At 600 it can be quite handy, I use mine to watch mirage between shots. I then use it when scoring.
Position behind the rifle is also a factor. Some folks like to have the rifle at an angle to the shoulder and some like to be straight behind the rifle. You'll have to decide what position works best for you.
You shot a 581, which is quite good.
Was that factory ammo or reloads?
Do you plan to shoot at longer ranges?
All of these play into your "Big Picture" plan for shooting.
These are all suggestions.
My advice is next match look around at what everyone is using and ask questions- why did you pick that one, etc. Most shooters are more than happy to help new shooters out by answering questions.
And I have exclusively shot .223 since I started, so I am well familiar with it. But being a Match Director has hampered me shooting the last 3 years, so I have not achieved High Master yet. I am a Master though.
A .223 is a lot of fun to shoot and when you beat the .308's it's a bigger smile.
Best of luck!
Rick