.243 in an AR-15???

[BigDave]

I know Armalite does, or did make an ar in .243.  Has anyone used this in three gun???  I assume it is a bit larger cartrige that the .223 Rem.  It would likely be a LOT easier to make major, not to mention more effective on long range steel.  Any opinions here?

[DBChaffin]

Dave, major for rifle division is 340 PF and minor is 160.  The .243 can't make major as far as I know, since a 100 grain at 3000 is only a 300 PF and lighter weight bullets are even further away.  It might buck the wind a bit better than a .223, but I don't think there would be enough advantage to try it.  Most people that shoot major shoot .308.  A 7mm-08 might do what you are looking for as it could make major, but again I don't know that the benefits would be enough to outweigh the cost.  Pretty much it is .223 in minor or .308 in major that I have seen, with a few pistol caliber carbines in minor to round out the field.

[kellyn]

You'd have to really crank a .243 to make major ( a 107 at 3177.5 fps).  Ruptured cases, blown primers, cracked bolts, it wouldn't be pretty. The ultimate major rifle cartridge has yet to be developed or used.  A .25 or 6.5 with a 110-120 grain bullet?   A 110 grainer has to go 3090.9 fps and a 120 has to go 2833.3.  A 6.5 X 55mm anyone?  A .260 remington?  Still a lot more recoil than a .223.  With the current power factors, I don't see .223 getting knocked off the top of the heap in USPSA 3 gunning.  Plus .223 is so much cheaper to shoot.

I disagree with the notion that .223s are less effective on long range steel.  Modern .223 bullets (69 or 77 gr. Sierra, 75 AMAX) are as wind resistant as most .308 bullets when fired at .308 Winchester velocities. They are close to .243s and 6.5s - which only really start to show significant advantages at ranges far beyond most 3 gunning.

Luckily some matches (SOF, Myst Mtn. 3gun, WC 3 Gun) don't have power factors.  .308 is major, .223 minor.  Bring on the 110 grain bullets!