Me too. As I hunt the Lower Saxony state forests, I had to use "unleaded " bullets for 4 years now. I too have used the 270 gr Hornady RNs and still have several hundreds stored away. But by regulations I was forced to change to an available pure copper bullet. As I found, the Barnes TTX bullets have a "curvy", tangent ogive point with a small "flat" hollow point. If seated out to the max oal the M1910 magazine allows, the bullets are held reasonably close to the follower spindle by the bullet guide. Yes, my loads work in the M1910 magazine. Granted, the Hornady RNs worked a bit smoother, but there is little choice now.
Such pure copper bullets are much longer than conventional lead core ones of the same weight. The 235 gr TTX is longer than the 270gr RN, but seated out in the 9x57 M-S = .375 Rimless NE it just fills the case neck. The longer 270 gr TSX protudes into the case body, eating up powder space. So I could not load more than 50 gr N140 behind the 270 gr TTX, giving away a lot of velocity. My load, with the 235 gr TTX in front of 55 gr N140, reads out 2400 fps from my 50 cm = 20" barrel over my chrony.