A friend of mine shoots IPSC 3 Gun, and since he's shooting an AR, is in the Minor Power Factor. Power Factor is determined by bullet weight in grains times velocity, divided by 1000. You must have 340 or above to be considered in the Major Power Factor. Since there's no way we're going to try driving a 55 grain bullet to 6181 fps to bump him up to Major, the only avenue is to go with heavier bullets, much heavier bullets.

Punching up the calculator, and assuming we're pushing a 220 grain Match King, we'd have to spit it out at 1550 fps, and add on a bit more to give some leeway for deviation between rounds. To gain extra velocity, a 20 or 24" barrel would not be a problem, since it would give a longer sight radius than a 16" carbine barrel anyway.

Even with a 20 or 24" barrel, is it possible to drive a 220 grain Match King up to that velocity at all? Are there other bullets in the 220-240 range that are shorter and would allow extra powder capacity? Are there any suitable powders to accomplish this? Would we have to use a banded boreriding bullet, like the GS Custom HV Hollowpoint? Our heart isn't set on the 220 grain Match King, the only real plus to using that bullet is Sierra isn't very far, and uber cheap factory seconds are available in bulk.

Looking at the data in the "Cartridges of the World, 9th Edition", I think you will come up short of your goal. It lists the 125 Nosler BT at 2283 (power factor = 285) as the max load for the AR-15, and the heavier bullet loads are all subsonic loads, not max loads, so I wonder if the heavier bullets have to be seated much deeper in the case in order to fit the AR-15 magazine.

But the people to talk to are at SSK , they invented the 300 whisper and know it better than anyone else.

Added : You wouldn't want to use the GS HV bullet, it's copper and very pointed, so it is a very long bullet. The GS flat-nose solid would be much shorter for it's weight. Instead of using Sierra's Matchking bullet, have you considered the 220 grain Round-Nose? It's much shorter for it's weight, giving you more case capacity when seated to fit the AR-15 magazine. How long is the maximum shooting distance for IPSC 3-gun? If it's under 200 yards the RN really doesn't drop more than the Matchking, and even at 300 yards the difference is only a couple of inches. Yes the BC is much lower, but unless you need to go over 300 yards it really hasn't taken effect yet.

[ 07-07-2003, 09:16: Message edited by: CMcDermott ]

Looking at the load data I've found on the web, the heavier I go, bulletwise, the closer I get to making the power factor. I think the max distance is around 200 yards.

http://quarterbore.com/300whisper/supersonic.html

From that, 15.6 grains of AA 1680 pushed a 220 grain SMK to 1492 FPS, from a 16" barreled AR. I think with a 20" or 22" barrel, it might just be enough to make it. Of course, the 220 grain SMK's are very long bullets, and that does eat into powder capacity.

I'm somewhat hesitant of the soft round nose bullets, as they might have trouble feeding from the magazine.

I think this can be done, it's probably just a matter of throwing enough time and effort into load development(and a couple hundred bucks into dies/barrel, and adjustable gas block).

How about a 7.62X39 w/ fast twist to use heavier bullets? You can also set it up to shoot .308" bullets. The case should be sufficiently large to achieve the power level you are after.

The problem would be feeding the rifle then. The 7.62X39 slopes much more than the .223 or .300 Whisper does. Regular AR mags wouldn't work, and high cap 7.62X39 AR mags are a bit of a rarity.

30/222 with 123/130 bullet can perhaps feed in a AR15 with low cost case in 222 rem than 221

I agree that 7.62x39 feeding in a AR15 is a nightmare

good shooting

DAN TEC