600 yards - NRA MidRange High Power match with 6.5 Grendel - mixed results (big post)

[lazyengineer]

(long post - so bewarned!)

This weekend I fired at a 600 yard Midrange match. I had chance to fire the Grendel as well. I learned a lot.

Background:
Course of fire typically is 20 rounds (+sighters) at 600 yards, fired one shot at a time. This is a structured event where rounds are fired from the prone position with competitors all abreast in a timed course, of 22 shots (2 of which are sighters), fired in 22 minutes. And each shot into the paper target 600 yards away is marked (note 1st picture); so you can see where you hit every shot, and adjust as you go.

Each 600 yard target frame is about 3' across.

Here's a generic internet photo of what it really looks like, 600 yards away:


I took my standard National Match 5.56 20" AR15 (Service Rifle category gun); which is fired from the prone position using a sling for support, and a 4X scope. For comparison; here's how the Service Rifle shot:

Record sheet from 5.56 AR15 at 600 yards - 20 rounds fired + 2 sighters.
80.5gr Berger @ 2770 FPS, 0.82 seconds flight time.

Which of the 20 rounds fired, came out to a score of 198-11x. This is good. Note the grid lines are in MOA; which is to say each line represents 6 inches @ 600 yards. (the S2 in the 9 ring upper left, is the second sighter shot)

To topic: What I was excited about was bringing my 20" Monster BBL'd Grendel, and firing it as well - with it's much more attractive Ballistic Coefficient. I was hoping to shoot this good. One thought was to shoot the Grendel in the AR-Tactical category during one of the three 20-shot strings that will be fired this day. AR-Tactical is a new category in this style match, which allows a shooter to fire with a bipod and up to 15X optics, at the same target. i.e. don't HAVE to use a sling, and not limited to 4X max magnification by rule (unlike most of the other categories). Anyway, I ended up shooting the 5.56 National Match for record in the end. But, as it turns out, I had opportunity to fire the Grendel anyway, when one of the other competitors had to withdraw early.

So for 22 minutes, I had a guy pulling the target at 600 for me, so I could get zero's with various loads, and also see how well this gun really shoots at 600 yards - a nice opportunity.

Here are the results from that.
Scope is a Primary Arms 2.5-10X GLx series, with markings in MIL (not MOA).
Rifle is: Anderson lower, BCA stripped upper (for tight BBL fit), TEAM Monster BBL and bolt, PSA Bolt carrier nut and handguard, graphite bipod, LaRue 2-stage trigger, Magpul CTR stock, Aero Precision Buffer on an Anderson lower. ELander mags (though single loaded thru ejection port per competition rules for 600 yard slow-fire)

I will say, there is a skill to shooting a bipod; and I'm still mastering it. When you shoot a sling, the tension of that forces a very consistent hold and addressing of the rifle. Shooting off a bipod and you can address the rifle much less consistently, and load it less consistently, unless you're skilled at it. Also, it seems like a bipod run gun can really jump up off the concrete - the consistency of which may be an item as well. So for some of these strings, I fired off a ruck-sack (which is also AR-Tactical legal), vs the bipod, but still got similar results.

65-Grendel: 95gr VMAX: 27.0 gr LT-32 @ 2710 fps

Shot 1 was actually still a sighter and I adjusted after that shot. So shots 2-5 are circled. As you can see, 2,3,5 are actually QUITE good. But shot 4 isn't very good. Giving the total group size of just four shots roughly 2 MOA. I might have actually shot that in competition, if this were my initial test string. While I generally take a dim view on discarding unpleasant shots, I can't say for sure if shot#4 was or wasn't me and the bipod.


(cont - image count limitation)