Best AR15 Caliber for Med-Long range Steel Matches

[jrob300]

A while back I built an 18" precision upper for my AR. It is more than I could ask for and shoots lights out to 750 yds. The problem is... we have a hard time spotting hits on a tired steel plate. 77 gr. pills make almost no ring and unless the plate is clean and white, spots are a bitch. In addition, the 77's get played almost as bad as 168's from a .308 in the wind.

I'd like to use this platform to shoot a local steel match, but I don't trust RO's to spot hits accurately with these tiny bullets.

MAX range is 850 yds. Spotting hits is imperative.

What caliber available from an AR15 platform will be workable? Notice I didn't say best, because the 6.5 Grendel will most likely be *best*.... but will the 6x45 be "adequate", or will it just be the next level of frustration?

All input welcome.... just don't stray into the .260/6.5cm/.308 end of the field as it IS NOT an option.... only .223/5.56 based lowers need apply.

John

 

[FCS]

IMHO the 6mm AR is probably the best all around cartridge for running out of an AR-15 platform. I'd suggest a +2 gas system and 22-24" bbl.

6X45 you are limited to little bullets, heavies are going to seat with ogive below bottom of neck/shoulder when loaded to AR mag limit.

 

[jrob300]

6X45 you are limited to little bullets, heavies are going to seat with ogive below bottom of neck/shoulder when loaded to AR mag limit.

This is exactly the kind of info I'm looking for... so 105 BTHP's won't work? What are the heaviest/highest BC bullets I can run?

Thanks for the info....


John

 

[FCS]

75s for sure, 85-87s maybe when loaded to AR mag length.

I was looking at doing a 6/223 set up for 105 JLKs, need 2.700" OAL to make that work. Easy in a bolt rifle, not so much in an AR.

Other option might be 6 Hager, I'd still go 6mmAR for Lapua brass and small primer pocket.

 

[LRRPF52]

The 6mm's are great for cutting paper at distance from long barrels, but retained energy with a good weight bullet is going to register impact better on-target as the distance increases. The 77gr SMK sounds like a small child threw a pebble at the targets once you start getting out past 300yds.

For an off-the-shelf solution, the Grendel is hard to argue with. The 6x45 will be limited in projectile weight, which is already a problem for you.

If you are able to get one, a 6.5BR would be really nice, but parts availability is an issue, and you will be limited in mag capacity compared to the Grendel or 6mm variants like the Hagar and 6mm AR.

With the Grendel, you can run a 20" gun and still get 24" book velocities. Any of the 123gr target pills will run out to 2630fps from most 20" pipes, and if your matches are in NW Montana, you're looking at a lot of 6000ft + elevations, where bullet drop is significantly less than at sea level.

You will not hit as hard as the magnums or .260 Rem, but a 123gr .510 BC pill impacts steel with much more authority than a 77gr SMK. I run a lot of DM Courses, and get to see a lot of 77gr and 75gr 5.56 impact steel, as well as .308 and 6.5 Grendel for comparisons...just spent the weekend doing exactly that, so I know all too well what you mean by the anemic performance of 77gr on steel.

The Grendel hits with 716ft-lbs of energy at 850yds at 6600ft ASL in 75 F Temp when fired at 2630fps. The 168gr SMK hits steel at 850yds with 893ft-lbs in the same conditions when fired at 2650fps. That's 80% of the energy of 168gr SMK at 850yds, with 50% of the recoil, AND you beat it for wind drift and drop.

123gr .510 BC, 2630fps, 6600ft ASL

       Range    Velocity    Energy     Trajectory         TOF          Drift
      (yards)     (fps)     (ft-lb)       (MILS)         (sec)         (MILS)
          0      2630        1889           0.00         0.0000         0.00
         50      2562        1793          -0.33         0.0578        -0.07
        100      2496        1701          -0.00         0.1171        -0.15
        150      2430        1613          -0.15         0.1780        -0.23
        200      2366        1528          -0.43         0.2405        -0.30
        250      2302        1447          -0.77         0.3048        -0.39
        300      2239        1370          -1.15         0.3709        -0.47
        350      2178        1295          -1.55         0.4388        -0.55
        400      2117        1224          -1.99         0.5086        -0.64
        450      2057        1156          -2.44         0.5805        -0.73
        500      1999        1091          -2.92         0.6545        -0.82
        550      1941        1029          -3.43         0.7306        -0.92
        600      1884         970          -3.95         0.8091        -1.02
        650      1829         914          -4.50         0.8898        -1.12
        700      1775         860          -5.07         0.9731        -1.22
        750      1722         809          -5.67         1.0589        -1.33
        800      1670         761          -6.30         1.1474        -1.44
        850      1619         716          -6.95         1.2386        -1.55

168gr .308 SMK, 2650fps, .462 BC, same conditions

       Range    Velocity    Energy     Trajectory         TOF          Drift
      (yards)     (fps)     (ft-lb)       (MILS)         (sec)         (MILS)
          0      2650        2620           0.00         0.0000         0.00
         50      2575        2473          -0.33         0.0574        -0.08
        100      2501        2334           0.00         0.1165        -0.16
        150      2429        2201          -0.15         0.1774        -0.25
        200      2358        2073          -0.43         0.2400        -0.33
        250      2288        1952          -0.77         0.3046        -0.42
        300      2219        1836          -1.15         0.3712        -0.52
        350      2151        1726          -1.56         0.4398        -0.61
        400      2085        1621          -2.00         0.5107        -0.71
        450      2019        1521          -2.46         0.5838        -0.81
        500      1955        1426          -2.95         0.6592        -0.91
        550      1893        1336          -3.47         0.7372        -1.02
        600      1831        1251          -4.01         0.8178        -1.13
        650      1772        1171          -4.58         0.9010        -1.24
        700      1713        1095          -5.18         0.9871        -1.36
        750      1656        1023          -5.81         1.0762        -1.48
        800      1601         956          -6.47         1.1683        -1.61
        850      1547         893          -7.16         1.2636        -1.74

If you're not going to reload and deal with an oddball brass, Grendel is your ticket. If you are going to reload, I still think the Grendel makes a lot of sense because it's easy to find a load for quickly, and it hardly eats powder, so it's extremely affordable to load for, especially with Lapua brass, which will last you many reloads as long as you stay within max pressures.

You can also shoot the Grendel all day, day after day, with no recoil fatigue. A configuration like this would serve you well:

 

[Jon A]

Are you going to reload? I shot the JC Steel match (75 yds - 1150 yds) with a 6mm AR Turbo and did pretty well:

I was impressed with how it did and I wasn't even shooting full power loads yet. As a longtime Grendel shooter I like that round a lot and if you're going to use factory ammo it's a no-brainer. But if you're going to reload the Turbo offers a usable advantage IMHO. The straight necked down 6mm AR offers a small ballistic improvement, the Turbo offers another small improvement over that...add them both together and it starts to become significant. Shooting 105's (higher available BC's than 6.5 123's) in the 2850-2900 range it makes for a pretty potent round.

Yes, the Grendel smacks the steel harder (especially with the 140's I used to like to shoot) but the 105's smack hard enough for matches IMHO. Spotting your shots is easy with this round even with no recoil compensation from a heavy rifle.

 

[proneshooter]

Avoid the 6BR or anything made from it by necking up and leaving the case otherwise unmodified. Making an AR feed reliably with that short, relatively untapered case is an exercise in frustration.

Get a 6.5 Grendel and go to town.

 

[Unknown]

I shoot Grendels at our local steel matches, but we only go out to about 550 yards. The Grendel has FAR more impact than the 5.56. At anything over 300 yards, the 5.56 doesn.t ring strrlmuch, but even at 550, the Grendel really smacks hard.

The 6mm version of the Grendel does not hit as hard, because it almost always has less bullet mass/energy. But even the 6x45, or the 6mm version of the Grendel are better than the 5.56x45. Of the two 6mm's, I think the 6mm Grendel would be better because you can seat heavier bullets in them.

 

[jrob300]

You guys are awesome. A lot of good data.

Yes I reload... it would be *nice* to be able to buy factory loaded Grendel ammo, but I'm not afraid of owning a wildcat either.

Some important information that might affect some of your advice (sorry for not thinking of this earlier): I'd like to keep the barrel to 20". I did the whole "17lb. Tactical Rifle" thing and it's awesome prone, but positional shooting sucks. My 18" SPR weighs about 11.5 with optic, bipod and ammo. I'd like to stay closer to that than not.

So... we are honing in on it... but if we hold barrel lengths to 20" how does that affect the 6mmAR and AR Turbo?

Jon A... what length barrel were you shooting 140's from a Grendel? That was the first bullet I thought of... it'll come out slow, but might end up being the best past 5-600 yds in the wind.

Keep those thoughts and comments coming.... I've read every post and am keeping notes...

John

 

[LRRPF52]

The 123gr will hit with more energy than a 140gr at 850yds, because the 140's start so slow from the Grendel. I hear you on being able to shoot positions. A 20" gun is really the limit if you are 5'10"-6' and medium build. As you get shorter, you need to start looking at an 18", then 16" carbine.

This is why I'm not a huge fan of the 18" SPR, even though it makes a great static position gun with a lot of velocity in 5.56 with the 77gr. It sucks to shoot positions with compared with a 16" barrel carbine, and I can make easier hits with a shorter gun.

There are a lot of stages where a 16" carbine in the right caliber will smoke magnums, because nobody can hold a 26" heavy-barreled bolt gun steady in positions, especially kneeling, seated, and I even have trouble holding my 22" .260 Rem AR10 steady while using a 2-point sling cinched down as hard as tolerable off a barricade in heavy winds. The gun is simply too heavy, requiring too much gross muscle input to keep it pointed in the direction of the target, without being able to find a steady NPOA that will facilitate hits, sometimes even at ranges where I have no issue hitting with a lightweight carbine from standing off-hand.

If you need the velocity to hit at 850yds, I would lean to the 20" gun, with a medium contour barrel balanced to your center of gravity. A 20" Grendel will push the 123gr pills to 2630fps. I'm not sure what a 20" 6mm AR will do, since the 6mm AR site says:

Typically, for highpower rifle competition at the 600 yard line, the heavy 105 to 108 gr. match bullets (without moly or any special loading techniques) shoot well in the range of 2750 - 2800 fps from a 26" barreled upper and provide much better downrange bullet performance than the comparable 223 long line bullets.

Looks like you need to go back to a 20" Grendel if you want the impact energy, and competitive drop and drift from an AR15.

 

[jrob300]

Yeah, in addition to what I've already learned empirically about bullet cross section, barrel length and velocity, I had also come across that quote about the round being developed for highpower and relying heavily on the long barrel for maximum velocity.... hence my caveat.

I'm coming to just that conclusion about the Grendel....

If anyone has contrary info... please... chime in.

 

[bustin]

A while back I built an 18" precision upper for my AR. It is more than I could ask for and shoots lights out to 750 yds. The problem is... we have a hard time spotting hits on a tired steel plate. 77 gr. pills make almost no ring and unless the plate is clean and white, spots are a bitch. In addition, the 77's get played almost as bad as 168's from a .308 in the wind.

I'd like to use this platform to shoot a local steel match, but I don't trust RO's to spot hits accurately with these tiny bullets.

MAX range is 850 yds. Spotting hits is imperative.

What caliber available from an AR15 platform will be workable? Notice I didn't say best, because the 6.5 Grendel will most likely be *best*.... but will the 6x45 be "adequate", or will it just be the next level of frustration?

All input welcome.... just don't stray into the .260/6.5cm/.308 end of the field as it IS NOT an option.... only .223/5.56 based lowers need apply.

John

Not sure you would notice much difference in a 95gr 6mm 200fps slower than a 77gr 5.56. IMO the 115s in a 6mm are too heavy for cases the size of the grendel or smaller.
I agree the 6.5 123gr bullets would be the next step up. Grendel/264 or 6.5BR or BRX.
We're working on a 270AR (based on the 6.5x47 case)that will push 130gr Bergers(.496BC) to 2700 out of an 18" barrel but it will be fall with things being as crazy as they are and it limits capacity to 10 cases in a mag.

 

[tmpohuski7]

What about the .25 wssm, 243 wssm and the 6.5 patriot? I have been looking for the answer to this question myself for a while now. A small frame AR with a 22-26" barrel that have close to 3 mils drop at 600 yards but traveling less than 3100 fps and feeding reliably from a mag.

 

[bustin]

Avoid the 6BR or anything made from it by necking up and leaving the case otherwise unmodified. Making an AR feed reliably with that short, relatively untapered case is an exercise in frustration.

Get a 6.5 Grendel and go to town.

Were you trying to make the 6BR feed from modified Olympic mags? I've been shooting a 6BRX since 2009 and have no problems.

 

[LRRPF52]

What about the .25 wssm, 243 wssm and the 6.5 patriot? I have been looking for the answer to this question myself for a while now. A small frame AR with a 22-26" barrel that have close to 3 mils drop at 600 yards but traveling less than 3100 fps and feeding reliably from a mag.

That's one of the biggest issues with the WSSM's.

 

[mavrick10_2000]

6mm bullets aren't easy to confirm hit's even out of a bolt gun caliber at 850. I'd pick a little bit larger caliber.

 

[Jon A]

Jon A... what length barrel were you shooting 140's from a Grendel? That was the first bullet I thought of... it'll come out slow, but might end up being the best past 5-600 yds in the wind.

I used a 24”. I ran relatively mild loads in the 2325-2350 fps range using TAC depending upon the weather. 2520 would beat that by about 50 fps at similar accuracy/guesstimated pressures. With CFE223 or VV N540 you can push close to 2400 fps safely I believe but I never had any of that on hand at the time.

They do well in the wind as well, but there is a downside to such a rainbow trajectory—your yardage measurements must be exact and small changes in weather will bite you more than with a flatter shooting round. Sometimes in the middle of a match having a little room for error can be helpful.

If you want to smack the plates the hardest, the 140’s will do that. The more meaningful number to look at for “smack factor” is retained momentum and the heavies always win that battle.

That said, the only time I or the spotter had problems seeing hits with my little 105’s at the above match was at the 1150 yd target but it was almost dark at the time-- and I wouldn’t have had a prayer hitting that with the Grendel anyway as it would have been long subsonic (close to sea level, cold weather). Most matches will have good spotters looking through a spotting scope. And I was seeing them myself at the other stages just fine through the SS5-20. I guess if you’re running a 3-9 or something it would be more difficult.

While I don’t think you gain much ballistically with 115’s from the 6mm, they will smack the plate harder. Should be indistinguishable from a Grendel shooting 123’s as retained momentum runs very close depending upon exact velocity/BC/range one chooses to compare.

Yeah, in addition to what I've already learned empirically about bullet cross section, barrel length and velocity, I had also come across that quote about the round being developed for highpower and relying heavily on the long barrel for maximum velocity.... hence my caveat.

All rounds need a long barrel for “maximum velocity.” Highpower shooters also always use long barrels for increased sight radius, regardless of the cartridge. There’s nothing about the 6mm that will cause shortening the barrel to affect it to a much greater degree than the Grendel—it’s still a long, long way from being remotely “overbore.” It’ll still beat the Grendel ballistically from any barrel length.

In fact, if you want a shorter barrel and look at it another way, the 6mm Turbo allows you to have a shorter barrel for a given supersonic range. While you may not plan on it, at some point in the future some match you go to may have a stage 1000+, and if you’re close to sea level and it’s chilly, a short barreled Grendel just won’t get the job done. Having the extra capability gives you a little more margin for error.

Don’t get me wrong, I still really like the Grendel, but for a reloader specifically looking for a round for precision LR match shooting, the 6mm AR Turbo offers a noticeable advantage IMHO.

 

[LRRPF52]

I took my 16" Grendel out to 1200yds this past weekend. Never thought it would do well out at that range, but it really surprised me. I've only shot it out to 700yds before, though I frequently make 1st-round connects with it at 500 and 600yds, as do new shooters who have little or no long-range experience.

I ran the ballistics for 1200yds at 81 F, at 4400 density altitude, and it gave me 14.4 mils elevation. My bullet was still supersonic at that range in those conditions. It's actually supersonic out to 1350yds in those conditions. When I plugged-in sea level and 30 degree temps, it dropped that supersonic range down to 950yds.

I'm using the factory 123gr Hornady A-MAX chronographed at 2460fps from my 16" 6.5 Grendel. I just missed the 1200yd target low with 14.4 mils, and made easy 2nd, 3rd, 4th, and 5th round hits on it as fast as I could index and break the shots. I will be playing with my little carbine at distance a lot more now after seeing that kind of performance.