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Interesting AR data today.

TimS

Silver $$ Contributor
Took my AR-15 out today to shoot at 300 yards.

I don’t reload for this rifle, have only experimented with purchased ammo.

I’ve had many loads shoot great at 100 yards. Stretch out to 300 yards today and the Black Hills ammo shot better than others even though the S.D. Was much higher.

The Lake City 62 green tips had a SD of 6.63 and averaged 3053 FPS and would not group minute of groundhog.

The Black Hills 69 grain had an SD of 24.53 and 2720 FPS. Had multiple groups within 1-1/2” @ 300 yards.

BTW. The rifle is a Colt 6940 with a Krieger 16” SS fluted barrel done by Compass Lake. Shot with an AAC suppressor.
 
I have thought about the numbers...(sd and es) but instead I let the targets tell me what bullet is best
as there have been many times where two different brand bullets would work well at 100 yards but one
would group better at the longer ranges. Seems the target tells me more than worrying about the numbers. :)
 
I've seen results like that too. There is defiantly a distance where SD doesn't play that large a part in POI. Up to that point you can have some pretty bad ES and still hit on point. I noticed this big time when I first started shooting my airguns for accuracy. No experience long range CF but from my understanding beyond roughly 300 (depends on many factors, but rule of thumb type thing) you want to keep your SD low as you can.
 
Before reloading I got good results from SAA (now owned by Nosler) 77gr Sierra's in 5.56. I was using it in a 20" barrel from JP Rifles. The green tip 855 is constructed with a steel tip in the bullet and I have never had it shoot well in anything. I suppose it is because it is hard to precisely and consistently manufacture a projectile consisting of a jacket, lead, and a steel tip.
 
That's because green tips are crap. I won't even shoot them. I either sell them or take them in for scrap. The steel cores are rarely seated in exactly the same spot.
Bet if you pulled those bullets and seated some match bullets in their place it would really hum.
 
TimS
Your target is telling you something and that is don't waste your time and your Krieger barrel shooting LC green tips. A Compass Lake build with a Krieger barrel deserves good ammo.
Sell or give that green tip ammo to a junior commando with a chrome lined AR barrel. Your target also told you that your rifle likes Black Hills ammo with Sierra bullets. Use the good ammo it's worth it.
 
All that’s required of military type (hardball, FMJ, “practice”, or whatever you call it, isn’t expected to do much better than “minute of a man’s chest” at 300. I treat it as short range defense loads. I’ve got a case of the “green tip” stuff that I keep on hand for my trunk gun (better than a handgun;)).
Your rifle sounds like it’s got good accuracy potential. I have used 69 grain match Partizan Prvi to shoot sub MOA groups at 300 out of my Stag Model Four. It’s very reasonably priced, if you can source it.
 
I'll add to what has already been stated above that the relatively short distance you were shooting also has a lot to do with your observation of good grouping despite high SD values. With a 69 Matchking, a 50 fps extreme spread (ES) would only be predicted to give you about 0.75" vertical dispersion solely based on velocity variance at 300 yd, which is well within your stated group spread of 1-1/2" with the BH ammo. Although the effect of velocity variance on vertical at 300 yd is certainly greater than at 100 yd, it's still relatively small as compared to the very nice half MOA grouping you achieved at 300 yd with the BH ammo. A similar ES value at 600 yd would be predicted to show vertical of more than 5.0". The shorter the distance, the less the effect of high ES/SD on the target.

Because you have a 7-twist barrel, I'd suggest giving a few factory loads with even heavier (higher BC bullets) a try; something loaded with Hornady's 75 gr BTHP or the 77 Matchking might also work out well for you. Like you've already been doing, testing a box each of a few different brands will usually be enough to identify one or two that clearly shoot better than the others.
 
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