About 4 years back Hornady discontinued the old style 6.5 Amax's and went to the new ones. All the new ones have a small polymer tip. The old style, very much liked by hunters (in cold weather they work well) just disintigrate game at long range so people liked them for that. I had a 6.5/300Wby that shot them fine in the winter but blew em up bad in the summer heat.
A while back on some forum, I remember someone asking if anyone had any of the old style "blow up" bullets for use in hunting season.
As a comparison, standing them side by side the bullets are the same length to the end of the jacket. The new bullets have an exposed tip that's about .115 in diameter and about .140 in length. The old style bullets have a tip that's .155 in diameter and .250 in exposed length, making the bullet about .100 longer than the new ones. The tips were poorly installed and these even have a seam between the copper and the poly.
The boattail on the old ones was about .060 longer also and it appears to have a little different ogive, though that's hard to distinguish. There is also more bearing surface on the old ones. To look at them side by side, you'd swear the old ones were 270's. They are either more empty (voids in the lead) or have lead that's less dense. They are considerably larger in exterior size.
I have about 40 of em left and perhaps someday I'll use em. I have no 6.5 now for a while yet, so they're safe for the time being.
FWIW, I haven't had the new ones blow up unless they were at 3400 in a 9 twist and in the heat.