New Cobras today

In my experience;
with both the Coopers AND the BFGs, they are good for one summer; IF you don't abuse them.
They will go hard in the second summer, or after the first couple of burnouts, but, long BEFORE the tire is half worn. (I would guess only the first 10% is any good, and possibly 10% more is sorta good)
After that it may take years of normal hot-dog driving for them to wear out, during which they will be totally predictable roller skates; and you can spin them for hundreds of feet, over and over, with little to no wear. and; they are super good at sliding, on account of they don't change with heat, and never dig, they just slide. At some point I usually put them on one of my other cars.
And the best part of all, is that a 295/50 has about as much rubber in the sideways direction as in the front to back; so, if I get into trouble while sliding, I just toe the clutch a lil, let the tires catch, and with a lil herky-jerky action, we are back. Whereas with 275s I was forever spinning out, with just the tiniest little bit of too much power application.
For you;
if you can fit 295s into your tubs on at least 10" wheels, I urge you to skip 275s entirely; they will only get you into trouble, in probably every corner, unless maybe your Scampy still has a 318 2bbl in it. You will think, from their straight-line action, that the 275s are not a bad tire, but in the turns, the 275 will reveal his true insidious evil nature, especially on a 7.5" (a 70%er) or smaller wheel, and 'round you will go.

BTW-1
a 295/50-15 is only a 295 on an 8" rim, which wheel, IMO, is way too small in anything but straightline action. Even on a 10" wheel, I have to run 24psi or less to get the tread of my 295s to sit flat on the road. But on a 10" wheel, my 295s are actually pushing 13" sidewall bulge, which is 330mm. If you try to run the 295s on 8 or 8.5 inch wheels, at optimum straight-line air-pressure, and in a straightline; the outter inch or so on each side, will, when spinning, lift off the road, and so may actually have less tire on the road than if you had 275s on the same rims.
In the turns, the above is what wipes you out.
With 275s on a 70%rim (7.5incher), as the inside 275 tire transitions from being say 8 inches of rubber on the road while not spinning, to 6 inches spinning, and the outside 275 tire, which now has most of the weight on it, rolls under and lifts the inside edge of the tire up off the road, and also becomes 6, or maybe 7inches. This happens so fast, you cannot humanly react fast enough, and so, 'round you will go.
It would have been better for you if you had just had 6inches of rubber on the road in the first place, and enough tire pressure in them that they stayed 6 inches in the turns. Sure they will slide, but at least the slide will be predictable. And if you get them spinning before the turn, you will not suffer a mid-turn catastrophic wipe-out ........ unless the vacuum-secondary carb happens to whack open,..... or shut, lol. So;
the take-away is this; for performance driving including turns, FORGET the 70% rule and go straight to 85%.

BTW-2;
Forget sliding;
>If you cannot play the throttle in the turns, or
>If you have a dirt-bike power-band, or
>If your CCP (Cranking Cylinder Pressure) is low. Unless you have a fairly hi-stall TC, or race gears out back. or
>with anything but a mechanical Secondary carb, cuz if the secondarys open by themselves, mid turn with rising rpm ......... surprise! around you will go again.
What; yur not into sliding? well, with 275s, if on 7.5s (70%), and a slightly warmed up V8, like it or not, you will soon discover sliding. Whether or not you like it, I cannot say...... lol