The other thread has deteriorated (shocking), so a new thread seems appropriate.
I started with an 87 Vmax seated to 2.715 COAL that would not chamber in the Cooper 243AI, trying to determine how short the throat is.
Here is that 87 VMax at 2.715 in the Cooper magazine, room to run:



I proceeded to bump the bullet by .005 at a time, stopping to check for a COAL that would chamber.

At 2.655 OAL, the bolt finally closed, .06 deeper than my starting OAL.

I took the sharpie and began searching for the magic little squares. 2.645 seemed to do things nicely:



I kept going down in .005 increments just to see how other depths looked. From top to bottom you are looking at 2.640, 2.635 and 2.630:



From what I could tell, things were getting pretty square in the 2.630 range as well. Of course, plenty of room in the magazine. No worries there:

Run that sumbeech and chase it as you go, IMO.

My Saami Rem 700 smooches at 2.73...

This was the only bullet I had time to play with. As discussed in the other thread, I'm interested in shooting the 87 VMax, 80/85 Barnes, 90 Lapua and maybe a 90/95 Ballistic Tip.

I did take the factory Winchester round that wouldn't play nice and found that it needed a .04 bump before it would chamber. So, depending on the bullet, the throat looks to be in the ballpark of .05 short.

Enough to make you send to back to Cooper? I don't know. I'm tempted to shoot it first, and let it talk on paper.

Thanks to those who helped with constructive input.

If it shoots the bullets you want to shoot well, and you're happy with it, just keep shooting.

Haven't followed the other thread, but unless you're stuck on factory ammo, consider yourself lucky to have gotten the short throat.

If you hand load exclusively, I'd leave it, especially being an AI. But that is only my opinion and I do not shoot much factory stuff. I'm sure others will chime in soon enough.

I like tight twist, personally, but 10 twist will stabilize what you want to shoot just fine. I've got an old 70 Varmint Sporter that was my 2nd Sammi 243 purchased many years ago (kind of a hybrid, heavy sporter barrel) in 12 twist that shoots 80 barnes very well when driven hard. Most would say that's nearly impossible, but it shoots them fine. I have other 6mms that I carry , so the Winchester is pretty much a dedicated varminter now. It's a coyote slayin' machine with VMaxs, and will need a new barrel soon...

I would let the rifle decide. But that's just me.

Like I said in the other thread, unless a bullet I really want to use needs to be too deep, i.e. the ogive is below the case mouth, I'd treat the short throat as a gift.

If you decide the throat is too short, it is no big deal to lengthen it. May be cheaper than the cost of shipping.

I certainly wouldn't worry about it. As far as the TTSX, if you seat it to the top groove, to match factory loads, it should have a decent jump, which they always like.

I'm sure you will be pleased at the results on paper. I wouldn't risk sending it back for a tiny bit of COAL length gain.

Why by an AI and figure on running factory plain ammo ? Blow out some brass and get a bullet comparator and roll

That pretty much the consensus with an AI.

And, you don't even need bullets to form the brass. The cream of wheat/ pistol powder method forms the case 99% once you find out how much powder it needs to make the corners nice and sharp. And many different powders work well.