I saw a write up on what all calibers could be done with a ar15 lower, but I cant seem to find it. can anyone direct me to it, or answer my question! thanks

Here's a list I found on another site.



AR-15, without bolt modification


.17 Remington


.20 Tactical


.204 Ruger


.221 Fireball


.222 Remington


.222 Remington Magnum


.223 Remington (5.56x45mm)


.223 Remington Ackley Improved


6x45mm


6mm Whisper


6.5mm Whisper


7mm Whisper


7mm TCU


.300 Whisper (.300/221, .300 Fireball)


.338 Whisper
AR-15, with bolt modification


223 WSSM


5.45x39mm (.21 Genghis)


243 WSSM


6mm PPC


6mm BR Remington


6.5mm PPC


6.5mm Grendel


25 WSSM


6.8x43mm SPC


.30 Herrett Rimless Tactical (6.8x43mm case trimmed to 41mm and necked up to .308; the 6.8mm version of the .300 Whisper)


7.62x39mm


.30 RAR


300 OSM


.357 Auto


.35 Gremlin (necked up 6.5 Grendel to 35)


.358 WSSM (various names, but all are some form of a WSSM necked up to
35 caliber, some are shortened to make them big game legal in Indiana)


.458 SOCOM


.50 Action Express


.50 Beowulf

To the above list i'd add:
7.62x40
30 carbine
9mm
45 acp
10 mm & 40 s&w
7.62x25
5.7x28
17 hmr

7.62 x 40 WT without bolt mod.

450 bushmaster

.50 BMG.

22 lr

can you do 300 blackout?

300 whisper

6.5 mpc
6.5 pcc
25x40
25 copperhead
6.8x40
6.8 ARK
7 ARK
25-223

6x6.8

338 spectre

Want to keep it simple, any rimless cartridge with an overall length of 2.300 or less is a really good rule of thumb. Some conversions are easier than others but if you have the time and money they can be done.
Two more not mentioned, the .475 Tremor and the .500 (actually .510) Phantom.

what do you have to do to the bolt to get 6.8spec to work?

You need a 6.8 bolt, barrel of course and magazine.


And whats this bolt mod stuff that was said?? You can't modify the bolt, you just get the right bolt for the caliber(s) you choose to have. You can't 'mod' a bolt, that I know of, to get it to work with a different caliber. Although some calibers have similarities, like having the same bolt....but theres no real 'bolt mods'.  

not sure about the mod, first posted said, without mod and then a list with a bolt mod. I figured you would just get a BCG per caliber

Yessir! That's along the same line of what I was thinkin.

Of course you can modify a .223/5.56mm AR bolt if you know what you are doing like a machinist or a gunsmith etc.

But of course what the original poster answered should of been phrased differently, for example the 6.5 Grendel,
the 6.8mm SPC use proprietary/specific bolt face diameter meant for that case...

Many times these bolts are simply 5.56mm bolts that have been bored to the correct diameter/depth for the  larger
case heads etc., and thus are In fact modified AR-15 bolts...

Yes.  Uses the same bolt as the standard AR.

ARFCOM Beginner's FAQ

15) How many calibers can I get uppers that fit my .223 (AR-15) lower? What are they?

While the list is nearly endless with all the wildcats possible. Here are the some of the more common and more interesting uppers that are (or have been) produced for the standard AR-15 lower (may not be up-to-date):

223/5.56
6 x 45
7 x 40
357 Mag Rimless
300 Whisper / .300Fireball / 300-.221
6.5 x 40
.30 Coyote (30 x 45)
.17 Remington
.17 Mach IV
.20 Tactical
.19 Calhoun
5.7 FN (developed by Rhinland Arms - no word yet on who is going to mfg it)
.204 Ruger
6.8 SPC
30 HRT
338 Spectre
10 mm Mag
35/40
219 WASP-C
7.62 x 40
5.45x39
7.62 x 39
.338 x 39
6 PPC
6.5 Grendel / 6.5 AR / 6.5 PPC Improved
22 PPC
7 sCAR ....
30 Carbine
5.45x39 / .21 Ghengis
7 BR
6.5 BR
300 Sabre
8mm (belt fed upper)
.308 (again a belt fed upper - no longer available)
458 SOCOM
44 Mag
440 CorBon
44 AMP
.475 Tremor
50AE
499LW
50 Beowulf
.50 BMG (single shot)
.50 Blackpowder (1 made)
9mm
45ACP
32ACP
22 LR
17 HV
10mm
7.62x25
224 BoZ
7.62x24
9x23
.357 Sig
.357 Auto
40S&W
223 WSSM
243 WSSM
300 WSSM
.30 RAR

To take this a little deeper...which of the above calibers use the same bolt as a standard AR15, *and* can be reloaded by reforming 5.56 and/or .223 brass?

I know .300 Blackout fits this criteria...any others?

Maybe we can get the list in the FAQ updated to separate them by "Uses standard bolt", "Can be reloaded using standard brass" and "Uses standard bolt, and can be reloaded using standard brass"?