6mm or 243AI?

[Partagas]

I am considering this for a long range varmit cartridge. I always thought the 6mm was under rated and much better ballistically than the 243. After reading on this site about the 243AI and factory brass for it, what is the difference between the two? Is a 6mmAI that much better than a regular 6? Advantages...disadvantages?
Thanks

[Jake in NC]

.. Basically, tweedle-dee or tweedle-dum.. Some will claim huge differences but when realistically investigated the differences are mostly cosmetic and statistical.. The .243 has better brass available from Lapua closer to a ready state than the 7x57 Norma available for the 6AI..
... Both are used with great success and I've enjoyed my 6AI 14tw.. Pick the one ya like the looks of and have at it.. d:^) JiNC

[chris matthews]

I would pick the 243 AI just beacause of the high quality brass and it's readily available. Both are good, accurate rounds.

[Varmint Hunter]

I chose the 6mmAI and went with the Norma 7x57 brass. My Hart barrel had a 12" twist and shot very well with 55gr-80gr bullets. The 55gr B-Tips can be (safely) shot so fast that they are flatter, and resist wind better, than the heavier bullets all the way out to about 750yds. After that the heavies take over.

Fireforming can be a pain in the neck. But if you're comparing the 243AI to the 6mmAI, then you would have to fireform either way.

The 6mmAI does have a moderate velocity advantage over the 243AI, if that's important. In a custom rifle either cartridge is capable of superb accuracy.

I hope I haven't just made your decision a little harder. [img]images/icons/rolleyes.gif[/img]

[rwleonard]

Hey Varmint Hunter,

When you say the heavier bullets take over after 750 yards, what do you mean by heavier? Are you talking heavier BTs (70-80grs), 90gr Bergers, or 100+ grain VLDs, or all of these?

I am just getting started this season with my first 243AI, and am trying to settle on "the load." I am looking for it to cover out to about 750 yards or so, after that I'll pull out the 300WSM.

Thanks. Rick

[Varmint Hunter]

Yes - by heavier I was refering to bullets from70-80gr. I have not looked at the ballistic charts for the real heavys (105-107gr) because my 12" twist will not stabilize them.

The 243AI will shoot a 55gr B-Tip bullet in excess of 4,000 ft/sec. If you do a few comparisons you will notice that this bullet will be flatter and more resistent to the effects of wind than most heavy but slower bullets out to about 750yds.

You would have to check on the VLD's but I doubt that they would beat the 55 grainers at their far superior velocity.

VH

[rwleonard]

I have a 1-10" twist, so 90 grainers are about tops for me. I am getting ready to try out some 90 gr Bergers and Lapuas, but now I think I'll try some 55 BTs in the mix and see what looks best.

Thanks, Rick