The old X bullets were notorious for severe copper fouling and poor performance in animals. Numerous reports of a failure to expand and just zipping through animals. Not in every instance but enough to be a bit leery about hunting with them. I've never shot them so could add nothing that isn't anecdotal to the responses.
Both of those "old wive's tales" are true about the original X-bullet design...to a certain extent.
Yup, they do foul more than a regular gilding metal jacket and somewhat more that the TSX design. I wouldn't say severe though and I've been using the original X design since the early 90s. That comes from the guys that started using them without reading the manuals that clearly state that they do foul more due to the softer pure copper material...or even if they read it, they didn't realize that good ole Hoppe's 9 won't cut the mustard, erm, copper fouling.
And yes, the failure to expand reports were common for much the same reason. Reloaders failing to follow Barnes' recommendations.
As a general rule, when using any of the Barnes X designs (original, TSX, or TTSX) you should choose a lighter bullet weight than you would normally select due to the "tougher" construction of the design.
In the case of my .257s, the 80gr is an equivalent of a 100gr jacketed lead-core design. The 100gr is equivalent to a 115/120gr, etc. (I use 100gr X or TSX in my .25-06 for whitetail, but it works on elk too. Hits like a 120gr Winchester PP and hold together real well when breaking shoulder blades.)
In the .277s, the 110gr is equivalent to a 130gr jacketed and the 130gr is equivalent to a 150gr.
Believe me; the X bullets are NOT TSX's. I love them. They work up well on the bench and favor being driven right at the upper edge of the performance envelope, they hit hard and have a good b.c. When you hit something like a big hog it usually puts 'em down in their tracks--D.R.T.!
I would use them over any other bullet made except for the Nosler Accubond and I think it even has the edge over the Nosler. I would suggest to try again and work up HOT with slow powders to get the accuracy where you want it. Typically my groups are 3 rounds touching at 100 from a cold bore shot clean. You REALLY have to clean the barrel--no using Hoppe's No. 9--I like the CR10 bore cleaner but be warned it's pretty nasty.
You are correct that the original X bullets like running on the ragged edge and that some rifles just plain don't like em.
My best groups out of several rifles with either X or TSX/TTSX are after a couple fouling shots. I've always got a couple flyers on the first two or three shots off of a clean bore, after that, they'll settle into nice groups for at least 50 rounds.
Back to the OP though....
If you decide not to use those old X bullets, be sure to post them up in the buy/sell/trade forum here. Someone might be interested in them.
If they were .257s, I'd be interested but we've only got one .270 here and it doesn't get many rounds put through it.
(gotta correct my earlier post. I'm using the 130gr TSX in dad's .270, not 120gr)