BCM 18" SS410 Accuracy at 600 yards

AR/M4 AR General Discussion
1

I am posting this for a friend who wants to purchase a quality SPR-type rifle. He wants an 18" BCM SS upper, Geiselle trigger, ADM mount, and Nightforce 2.5-10

I’ve shot many AR15 type rifles at 600 yards, but I came to realize that I’ve never shot a “legit”, quality rifle properly setup for that distance. It’s always been goofing off with a 10.3" and T1, or a 12.5" and TA31, or a 16" chrome lined with iron sights.

At 600 yards with quality handloads, what type of group size can be expected at this distance with the above setup? I want actual figures from people who have done this, not guesses. This guy is hoping to hang with my Krieger bbl .308, :bad: , does he have a shot?

How consistently could he hit a 4" gong, for example?

2

I might not have the exact distances you are looking for, but just last weekend we were ringing a 8 inch target at 450 yds. 90% accuracy. BCM SS410 16". SWFA 1-4 using Wolf Gold and AE.223. My 75 gr (hornady) hand loads are about MOA for me. A better shooter could do better for sure.

3

I appreciate that. That’s decent given the ammo.

My statement regarding no guesses what meant toward internet commandos.

4

My 16" BCM SS upper runs 3/4 of a minute with CBC 77g OTM. So in zero wind, doing my part I’d be super happy with a 4.5" group. You’re not going to be able to do that without match ammo.

But the wind is going to be the biggest issue with 5.56 at 600yd. At 600 with the gun above, with 9mph wind my hold is 5.9mils. If I call it at 10mph my DOPE is 6.6mil. That’s ~5.48cm for being 1 mph off in your wind call. May not matter if the wind is consistent and you can walk onto the target, but again usually wind is changing.

5

I have a 20" that I turned the barrel down to .750 under the hand guard. No problem shooting 1/2 - 3/4" @100 yards. No problem hitting prairie dogs @ 500 with 55 grn hornady hand loads. My 18" JP barrel is even more accurate but also more money.

6

Ask Markm or Pappabear. They were doing some crazy no shit long distance stuff out to 1000 yards.

7

Weren’t they doing some of that with a 14.5 barrel too?

Sent from my Nexus 6 using Tapatalk

8

I just bought the same BCM 18" upper with the ss barrel and 1/8 twist. I am going to scope it with a Trijicon TR24G. This is going to be my DM/Coyote gun. I am looking for any load info for 77 gr. OTM’s or Hornady 55gr. VMatch bullets using Varget powder. MARKM please chime in ?

9

Also not exactly what you are looking for but my buddy has an 18" BCM SS upper topped with a Razor HD gen1, SSA-E trigger and this past weekend he had no problem ringing the 14" steel at 660 yards over and over. This was with CBC 77gr. OTM ammo. With the right handload, trigger, and shooter a 4" gong at 600 should be doable. At 600 his wind calls are going to have to be tighter than yours with heavier 30 cal bullets.

10

Good to hear, I have an 18" BCM upper in the pipeline right now.

11

With match ammunition that upper should hold sub 1" grouping at 100. As mentioned the limiting factor is bullet choice and the ability to read the wind and apply the correction/hold. Do take a look at various bullets though-long range they make a big difference. Go to JBM and compare them and see what they do in the wind. I try to break it down further than the stated difference in drift at 600. So let’s say drift is 2 mils for a bullet with a full value 10 mph wind, a 1 mph wind moves it .2, at/about 3" drift at 600-so a mis-judge of 1 mph equates to a 3" error on target. For info from Litz’s book, 1-2 mph judging error is considered elite. Break it down further-if one bullet drifts .2 mil less than the other, that mis-judge above cost you close to a 1/2" less on target at 600. Doesn’t sound like a lot but they (variables) all add up.
Bottom line-find an accurate and efficient bullet, drive it hard (fast)and read the wind well.
Check the new tipped SMK and/or the 75 Hornady BTHP since these are going to be mag length more than likely. Single feed-75 or 80 grain AMAX
Factory 77’s-Blackhills
Factory 75’s-Hornady match
While I can’t speak for the new tipped match kings, the 75 Hornady BTHP at equal velocity will be more efficient than the 77 SMK-the numbers don’t lie

JBM run theory numbers 10 mph full value wind at 600 @ 0 density altitude
77 SMK at 2900 fps(MK262 from my 24" bolt) 1.9 mils
75 Hornady BTHP match (factory) at 2750"" 1.8 mils
80 AMAX slow-2585 (reload) -1.7 mils-these are single feed
Big thing is look at the 77 smk velocity-that’s smoking-if I increase the velocity of the other two-very doable-the 77 smk can’t keep up ballistically.
the 77 smk at 2800 is 2 mils and at 2600-2.3 mils

Run the 1000 numbers and you see the 77 smk is an ok bullet, again the 75 bthp and or 75/80 amax is much better, no direct experience with the Bergers other than with .260/.308

12

That would be crazy where is that link at!

13

I bought a stripped BCM 18" SS410 barrel a few years ago that I built into an upper myself, including drilling/tapering the GB pin hole. It just so happens that the longest range I have access to around here is 600 yards. I can ping a 6" gong consistently at that distance. I have not shot groups that far though. This is with factory Winchester Ranger 69grn match. I have some hand loads in 77smk ready to go test with but haven’t had the time lately. The BCM barrel is good stuff.
By the by, using a Leupold scope I zeroed at 100 yards and using a ballistics calculator dialed in for 600 and was pretty much there. It’s just always windy at this place which plays with your shots some.