What calibers are best in the AR-15?

Actually the AR-15 doesn't host all those calibers, the AR10 is the base did the larger calibers.

5.56 close quarters
308 SPC
338 reach out and touch someone

.204
.223
6x45

I'm no expert on ARs, but I have been doing a great deal of research in hopes of purchasing my first inside a year.

AR-10 rifles largely shoot cartridges based on the .308 case (.243 win, .260 rem., .308 win, .338 Federal). Some are also chambered in the 6.5 Creedmor.

The AR-15 platform can be found in:
.22 lr
.204 Ruger
5.7x28mm
.223
5.56 Nato
5.56x39mm
6x45mm
6.5 Grendel
6.8mm SPC
7.62X39mm
.450 Bushmaster
.458 SOCOM
.50 Beowulf
various pistol cartridges
Olympic arms has a series that takes the WSSM series of big game rounds

As to what is the best? I guess that would depend on intended purpose and how well each round functions within the platform

I have ARs in 3 calibers-
22lr
9mm
223/5.56

That has been the best combination of affordability and enjoyment for me

Jason W....you missed the 300 BLACKOUT. A 30 caliber bullet with standard AR15 mags and bolts? Easy conversion and well worth playing with (imvho).

5.56 with a .22 conversion (does that count as one or two?)
300 BLACKOUT since they use standard AR15 bolts and magazines it's an easy conversion to shoot. You can get ammo from 125gr supersonics that are real close to 7.62x39 ballistics, and 220gr subsonics that are just fun to shoot suppressed. (Ballistics like a .45 ACP at the muzzle out to 100 yards or so.) Just a FUN round to play with.

I am considering building a 6.5 Grendel. Longer range ballistics look great, and now that it's SAAMI approved it may open up the market for some less expensive conversion options.

I also forgot the .30 remington AR

It really depends on what you want the AR for. My list:

.22 LR - I like .22s; plinking use

.223/5.56 - Standard AR fare with commonly available ammo; training and competition use

6.8 SPC - Increased power with little felt recoil and good available ammo; hunting use

223,762x39,22 adapter,458 socom he specified ar-15

Only 3?

.22 LR for plinking and training

5.56

458 SOCOM

he AR-15 platform can be found in:
.22 lr
.204 Ruger
5.7x28mm
.223
5.56 Nato
5.56x39mm
6x45mm
6.5 Grendel
6.8mm SPC
7.62X39mm
.450 Bushmaster
.458 SOCOM
.50 Beowulf
various pistol cartridges
Olympic arms has a series that takes the WSSM series of big game rounds

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I believe you mean 5.45x39

Others not mentioned above (but some may take a little more looking to find)

300 black out

300 whisper

30 HRT

338 specter

7.62x25

50 A&E

357 AutoMag

44 AutoMag

44 Rem Mag

440 CorBon

.475 Tremor

.17 Remington

.50 BMG

.338x39 caliber (I'm aware of only one ever made though)

I'm sure there are more I'm skipping.

I'd like one in .243 Winchester or 6mm Remington.

5.56 for sure, personally I need a 16" and a 20.
6.8 spc in a Bison 16" spr profile. Nice and light, 30% improvement in energy.
6 mm DTI ( 6 mm Dtech Improved, 6.8 SPC case necked down, and a 30* shoulder) but only if you like to hand load. If not get the .243 WSSM with a 24" bbl. GREAT deer etc. guns.

My 3 uppers are currently 5.56, 9mm, and .25 WSSM. I want a fourth but haven't decided on a caliber as yet.

I'd start with 5.56 in 1:7 twist bbl. for maximum versatility. Next I'd go to .22 LR for ultra cheap plinking, training, short range practice; basically everything you'd use any other .22 LR rifle for.

For a third caliber I'm leaning toward .300 AAC Blackout myself. 30 caliber bullets in necked up standard 5.56 brass (which also means it uses standard AR mags & bolts), with heavy backing from AAC & Remington (and the massive Freedom Group to which they belong) are why it appeals to me.

6.8 SPC is neat, but you can't form brass from anything else, and good mags for it are expensive. It does have good backing from Freedom Group though.

6.5 Grendel may be the best of the medium caliber AR-15 compatible cartridges, but Alexander Arms is controlling it so tightly that it's basically proprietary. 6.5 Grendel is the Beta Max of rifle cartridges. The 6.5 Grendel's parent case is the 6mm PPC, which has 7.62x39 as its parent case. So, you can make your own brass, but good mags will still be expensive & hard to find.

Between .458 SOCOM, and .450 Bushmaster, it just depends on preference. Some like the .450 BM for its .452" diameter bullets that are cross compatible with .45 ACP & .45 Colt for handloads. Others like the .458 SOCOM because there are more heavily constructed .458" diameter bullets for heavy game hunting. These bullets are also compatible with .45-70 Government, and other large game rifles.

.22LR --- just plain fun for plinking and a great starter rifle for just about anyone

For the handloader - 6X45 --- great for defense, varmints and whitetail deer

If you dont handload - .223/ 5.56 --- nearly as good as the 6X45 on varmints and defense. It may not be legal for whitetail in your state thou, always check local laws.

For the handloader - .450BM --- you can take it from target .45acp power or crank it up to smack pigs like the hammer of Thor.

If you dont hand load - .45acp or 9MM--- either one will work. Everyone should have a pistol caliber carbine.

the AR57 is not the cheapest option(upper costing $700 and rifle topping $1000) but it is certainly intersting. 50 round capacity, easy brass catching solutions, a light effective(imho) round, flat trajectory, and minimal recoil it might be worth giving a chance

ugaarguy said:

6.5 Grendel may be the best of the medium caliber AR-15 compatible cartridges, but Alexander Arms is controlling it so tightly that it's basically proprietary. 6.5 Grendel is the Beta Max of rifle cartridges. The 6.5 Grendel's parent case is the 6mm PPC, which has 7.62x39 as its parent case. So, you can make your own brass, but good mags will still be expensive & hard to find.

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Here's some up to date info on the Grendel. SAAMI has accepted the Grendel round. A Arms has released the trade mark. Wolf well soon release steel case ammo at about .30 a round. 17 and 25 round stainless/Teflon mags are readily available for under $15 each.



I've been waiting for this. I have two builds waiting for barrels. I well have a 10.5 sbr barrel ordered soon along with a 14.5 or 16.

Here's some up to date info on the Grendel. SAAMI has accepted the Grendel round. A Arms has released the trade mark. Wolf well soon release steel case ammo at about .30 a round.

Click to expand...

Just read that on The Firearm Blog. That happened, what, a few weeks ago?

17 and 25 round stainless/Teflon mags are readily available for under $15 each.

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Where from? I'm genuinely curious. I see the ones that PSA has, but any idea who the maker is?

I think you can do well with only two:

9mm - close in SD/HD, CQB, inexpensive range practice (and there is some discussion regarding 9mm having better penetration of objects than 5.56 at closer range...house distances...I cannot say)

6.8 SPC...or 7.62x39 (less expensive) - hunting, longer range engagement, penetration


Not an expert, just my opinion.

Respectfully,

J

IME 5.56mm is the best caliber in the AR. Very cheap to shoot and reload, uses the standard magazines available anywhere, on the shelf at every gun shop and Wal-Mart, works up close or a long ways off, and with the right bullet in the right place it will take a deer or a hog.

There are some great calibers doing great things in the AR, but IMO the original is the best in the AR.

Just my .02,
LeonCarr

5.56 Nato/.223
.22 lr CMMG conversion They work great. Why spend the money on a whole upper.
9mm

I'm also looking at the 6x45, and 30 cal. in 300/221, 300 whisper, 300 AAC Blackout. The 5.7 AR upper in very interesting but as already mentioned, it's a $700 upper. The rounds aren't exactly cheap either unless you reload. I'd like a 7.62x25, or .30 carbine upper just because.

Is that more than 3 ? lol.

.22 lr CMMG conversion They work great. Why spend the money on a whole upper. (sic)

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To save the wear and tear on my Noveske barrel, a barrel that costs about as much as a whole upper can be had for.

To not shoot a bunch of dirty 22LR through my primary gun.

Because most .22lr rounds perform better out of a 1:16 twist and most ARs have 1:7 or 1:9.

So I don't have to re sight in the rifle every time I change what I want to shoot.

Also, a complete lower can be had cheap enough and once you get that you have a whole separate rifle which can be nice.

I have 2 CMMG conversion kits that I shoot/shot with 1/7 twist barreled ARs. They work and are great for introduction shooting with newbies. Not very accurate and certainly IMO not squirrel accurate at normal range (20 yards) unless you do not care about the meat or an all out miss! Could be off a little on that have not shot the conversion kits for a long time.. Purchased the CMMG upper in .22 and have been pleased.

In the AR platforms I have .22, 5.56, and 7.62x39. I am not hunting long range for big critters or grizzlies so at the moment I feel like my bases are covered and do not anticipate another purchase of a different caliber..

• .22 LR for cheap practice, Steel Challenge, and introducing newbies to marksmanship.
• .223 for Multigun competition, defense, and general center fire shooting.
• Not too sure on the third option. Probably a tossup between 6.8 SPC, .30 Gremlin, or .300 Whisper.