I have a blank AR-15 Upper reciever, which I will be building into a complete upper, and I’ve been looking for a different caliber - something fun, yet useful. Within the ‘20’ caliber offerings (5mm to 6.8mm), the most common options in the AR-15 platform are either .223/5.56mm, or .300 Blackout. There are some alternative options, such as 6.5mm Grendel, 6.8 SPC, or .204 Ruger. Then there are some interesting-but-obscure variations, like the 25-45 Sharps, or the .277 Wolverine, or the (very new) .22 Nosler. There are also a slew of ‘also ran’ calibers, such as the .243 Super Short Magnum.
One of the things I’m observing is that with some notable exceptions (.243 SSM), the variations all lead up to very similar ballistic numbers. The .223 runs about 1200ft-lhf at the muzzle, the 25-45 Sharps runs about 1600, and most of the rest fall somewhere in that range. Most have fairly similar (for a fairly generous range of ‘similar’) distance performance too.
The .204 has a purpose, in that its extreme velocity makes it a flat-shooting, devestating anti-varmint round. The rest? They increasingly look like a bunch of near clones, trying on different dresses to try and stand out.
So - Long winded opening done; Has anyone an opinion on 1) whether there’s any point in stepping outside the common options, and if so, 2) what caliber would you suggest?
I’m looking for a general-purpose utility cailber that can punch paper or drop varmints. I don’t need a big-game round, nor am I looking for something uber-tactical - Just whimsical-yet-practical.
And yes- My ego is involved. I don’t wish to be either a clone of everyone else on the range, nor do I wish to be contacting some obscure factory in outer Mongolia to source my brass and dies.
Nylon 66’s start at around $400 these days.
OP: For your described uses, go with the .223. As you’ve already noted, the other choices aren’t radically different in performance. Ammo that is reasonably easy to find on store shelves, available in many different loadings, and is comparatively cheap is kind of a lot to give up just to have something a little different from some other guy at the range. The 6.Xmm cartridges that were developed for improved performance in military applications have caught my eye in the past; but, since my uses parallel yours, I stuck with 5.56mm uppers.
My suggestion is that you start your search with the bullets available for each caliber. Bullet weight is one consideration. Heavier weights fight cross-winds better than lighter ones, generally-speaking. High ballistic coefficient, or does it matter? Pointed, hollow point, round nose, fragile/frangible, boat tail, etc…
Are you looking for 1/2" groups, or are 1.5" groups acceptable? Or 3" groups but a whole lot of them?
Custom, and wildcat, dies are available from reputable suppliers in the U.S…
Some exotic brass may only be available when a manufacturer gets around to making a batch, and when it runs out, you wait until someone makes a new batch. .223 brass is always available.
Sub-MOA (~1" @ 100 yards, for those not in the know) is where I’m looking - Varminting usually involves small targets at longer ranges. The .204, for instance, has a nice flat trajectory, but the very light bullet weights factor into wind drift. On the other hand, the AR-15’s restrictions to case OAL (over-all length) has implications on bullet weight and profile, in that in order to obtain a good crimp, you need to be crimping on at least some part of the shank of the bullet, as opposed to the ogive. That limits bullet selection in some of the larger calibers - unless you wish to use compressed loads (I’m not practiced enough a reloader to be comfortable there).
This plays a lot into my thinking - Calibers which can use re-sized .223 brass are in effect as well-supported as the .223.
.223 is unfortunately for me, not my most precise round - Though that may be the design and component selection of my uppers. It could be that a better / more carefully-selected set of parts can give the .223 the accuracy I’m looking for. The amunition is, as noted, ubiquitous and inexpensive.
Are you using a .223 upper, a 5.56 upper, or one of the “split the difference” uppers? Is your barrel free floated? Also, are you using a matchgrade trigger? Are you firing from a bipod, a rest, or slinging up?
Note that the .300 Blackout cartridge was designed to generate minimum assault rifle ballistics in the lighter bullets while providing better performance than the 9mmP in the 220 gr subsonic bullet range. It is not a generally superior shooting round unless you are mounting a suppressor on your rifle and doing gun house shoots with USSOCOM operators.
I really like the 6.8 Rem SPC round as a middle range round between the ballistics of the 7.62 x 51 mm NATO and the 5.56 x 45 mm NATO. In many ways, it is a slightly downgraded .270 Remington but in a 5.56 NATO-sized cartridge, and performs well in the carbine length rifles that have become preferred in the AR-15 platform. It’s ballistic performance and accuracy has been well established, and the recoil and wear in the AR-15 is not much greater than the 5.56 NATO.
However, it is going to be considerably more expensive to shoot for performance that is not significantly better for most three gun and other competition shooting, for which the .223 Rem/5.56 NATO has been widely adopted and by carefully tuning the cartridge load and bullet weight to your gun and using a heavy barrel you should be able to get MOA precision out to 300 meters, more or less. Beyond that, and the bullet weight is going to drive loss of precision regardless of how well you tune it.
For long range varminting the .223 Rem just isn’t adequate, and you need to move to a flatter flying, higher velocity round in a dedicated bolt gun outfitted for the purpose. I’ve seen people try varmint shoot with AR-15 type guns at over 200 meters using carry handle mounted scopes and stock barrels, and by they time they are done they’ve spent as much on ammo as it would have cost them just to buy a decent varmint rifle setup (not including the optics, which will probably cost more than the rest of the rifle and mods combined).
Currently, it’s a blank AR-Stoner upper. I was planning on free-floating the barrel…
Oh, wait, you’re talking about my other upper. Free-floated CMMG, .223-specific (not ‘Wylde’) 18" medium-profile. The lower (also CMMG) uses a Geissele drop-in trigger pack, but that’s the extent of its customization. Yes, I use a bipod, and optics - 4x32 Burris.
Fair point, and one of the reasons I was reluctant to go that direction.
This is one of the attractive thing - I generally like both “quarter calibers” and 7mm. Truthfully, I might suggest that the calibers closer to 7mm would be better met in an AR-10 reciever. 25-08 or 6.8 Creedmore are potent. But if 6.8 SPC meets a varmint profile in the right build, that’s in the range of possible solutions.
Cost, or course, is a factor. The .22 Nosler uses the 6.8 SPC case, with a .223 bullet - energy levels fall inbetween the 6.8 and the .223 - at about 3000-3350 FPS, depending on bullet weight. It’s too new to have good reports on accuracy, and it still suffers the scarce case problem.
300 meters is good enough. Most of my varminting is under 250.
I’m deffo building this upper with accuracy as a major consideration. AR-Stoner upper, and it will be wearing some heavy glass.
If you’re reasonably satisfied with the bullet selection of the .223/5.56, check the muzzle crown for possible nicks. A reputable gunsmith can cut and reform the crown, if required.
You can also “slug” the barrel to measure the chamber, throat, and barrel. Or have a gunsmith do it. Force a soft (pure) lead slug thru the barrel (don’t screw up the muzzle), or pour molten cerosafe into the breach. Inspect the slug for imperfections, and size.
You can spend a lot of time and money trying to improve “how” a round gets into the chamber, but it’s the internal ballistics that decides how it flys, and how well it groups. If you’re looking for the ultimate in accuracy, a premium barrel is a good way to go.
Firing from a bipod with a 4x scope doesn’t give you the best idea of how your rifle is performing. Fire your .223 upper from a proper sandbagged rest and allow the barrel to cool completely between strings before you write off the .223 as not your most precise round. Any other round fired with that combo would likely seem pretty lackluster, as well.
I agree with Stranger on the majority of his points. I’d like to know what you are including under the heading “varminting” though. For anything smaller than a coyote, the 6/7mm rounds are overkill. A groundhog doesn’t require a round in the .270 class for a humane kill.
I didn’t mean to suggest that a .270 or 7mm round was necessary for varminting, and looking back through my post I’m not sure how it could be interpreted that way, but if it gave that impression then I apologize. Smaller hypervelocity rounds in the .224 inch category such as the .220 Swift and the .22-250 are ideal for groundhog and marmot hunting at distances exceeding 300 meters.
You didn’t give that impression. I was trying to put the useful information you gave into the context of his goals. Thus, I asked for his clarification.
Not an AR guy, at least not yet, but seems like you’re missing 7.62x39mm. Ammo is super easy to find, and it’s not an uncommon choice. It wouldn’t provide much over the .223 of course, and similar to 300BLK without the tacticool. Personally, I don’t buy that there is anything inherently inaccurate about that platform.
Either that or .22 LR if you really want to.
In the similar vein of .50 Beowulf, there is also .458 SOCOM. Probably doesn’t meet your price point though.
I know they sell 9mm lowers that take Glock magazines - I think you can still do pistol caliber on a regular lower though?
Back when I was a deer hunter (40 years ago), my rifle was a single shot .223 with a scope. I liked it because the round ended up exactly where the cross hairs where. So, a shot through the heart was easy to perform.
I chose a single shot to make it a fair fight, and to make sure of my target before I fired. But, I always had an extra round in my mouth, in case Murphy showed up.
Like I said, this was 40 years ago. And ammunition may have changed.
Woodchucks are the heaviest I’d be shooting, except very rare exceptions. Light brush or heavy grass is a common obstacle, though I try to NOT shoot through those.
