I read a lot about .243AI & how well they perform especially when it comes to case trimming. My question is, how much better, or not, would a 6mmAI work. Could a .243 be reamed out to 6mmAI?
Would a 10" twist barrel handle 100 grain bullets well enough?
Pros & cons ...?
Thanks

a 6mm reamer will not clean up a .243 chamber without setting the barrel back.

I have both, the .243AI twisted @ 8 with a very short throat and the 6mmAI twisted at 9 with a very long throat. To give but one answer to your first question- working better or worse is hard to establish. Please be more specific. Both of these rifles like every Hornady bullet I shove through them, however, the 6mmAI with the long throat HATES the Sierra 95gr HPBT. I cannot seat it long enough to touch the lands. The .243AI is just opposite and really likes the Sierra.

A common ground to illustrate whether there is a "better or worse" cartridge, one bullet that I use in both is the Hornady 87gr V-Max. Both rifles shoot this bullet at 1/4 MOA. The .243AI runs 3400 fps and the 6mmAI runs 3500 fps. The difference between my two rifles is that the 6mmAI handles the 105gr A-Max better than the .243AI and it handles the 75gr V-Max better than the 6mmAI.

Both cartridges are so close together in velocity per bullet weight that to separate them is like splitting hairs. It took a while to find the difference in them, but I did find it and it ain't much. Both of them have proven themselves with consecutive shots @ 800 yd prairie dogs. Have yet to try them at 1K.

Allen

Why not? I am asking out of curiosity, not skepticism. The head diameters are the same, the body taper is the same, the 6mmAI is longer, why can't you open up a .243 to 6mmAI without setting the barrel back?

Allen

My bad where I mentioned "Body Tapers" I had both AI's on the brain, not .243 Win to 6mmAI.

When opening up a 6mm Rem chamber with a 6mmAI reamer, the barrel needs to be set back one thread to accomodate the .004" shorter AI dimensions. If the .243 Win chamber is 51mm long, why won't the 57mm length reamer (minus the .004" for AI) "clean up" the .243 Win chamber?

It is getting late.

Allen

My bad, I was thinking regular 6mm Rem and not the AI version.

It will be close even with the AI version since the .243 measures .455" at the shoulder located 1.553" from the base.

The 6mm AI measures .451" at 1.76 from the base.

I could do the math but I think it would clean up if the original .243 chamber wasn't too generous.

The 6mmAI will clean up a 243 chamber.

Another alternative in the same clsss is a 6mmX284. It can ream out a .243.

The 6x284 is a good class ABOVE the 6AI.

Will the 6mmAI feed without any mods from a converted 243?

Thanks guys, for the education ...

Allen, this is what I was wanting to know. I'm wanting to use the heavier bullets for whitetails & this is good info. Could just use 85 gr TSX in the .243 but a 6mmAI sounds interesting.

Thanks again guys.

You seem to be doing a lot of this lately !!!!!!!!!!!
think before you type

HWYMN- note that Allen has a 1/9" twist on his 6mm AI and not the 1/10" that you asked about.

I mention that because I've tried the 105 gr AMAX (though not the 100 gr Interlocks you asked about in your OP) through a 1-in-10" twist and not had pleasant results. That 1 extra inch faster twist makes a difference.

Good luck on the project. That is something I've often thought made a lot of sense going from 243 Win to 6 AI.

You gotta be willing to offer answers to be wrong once in a while.

For those of us who ask a lot of questions (like me) I'm glad there are others like nsaqam who are willing to offer answers... particularly since he so readily admits when he made a mistake.

I'd sooner run a 243AI on a 2.8" short action, just for the OAL freedom with the longer bullets. With typical hunting bullets, the 6mmAI is fine in the same action. The one I had worked just fine with 100gr Hornady boattails.

Yep.

Amusing side note:

I missed a local CJ-7 this morning, similar condition to yours in the classifieds but brown with a tan hardtop. Similar price too. I dialed with frantic fingers but it was already snatched up. Nearly cried....