As previously noted, with a non-fragmenting bullet design like the TSX, heavier bullet weights are not necessarily better, especially at closer ranges and from shorter barrels. As long as penetration and upset remain adequate, it is possible to use lighter weight non-fragmenting bullets and still have outstanding terminal performance. With fragmenting designs, a heavier bullet is ideal, as it provides more potential fragments and still allows the central core to have enough mass for adequate penetration.
The 55 gr TSX used in the Federal (T223S) load stabilizes in barrel twists from 1/12 through 1/7, unlike the 53 gr TSX which is a bit longer than the 55 gr TSX, due to a different ogive and does not stabilize as consistently in all 1/12 twist barrels. The 55 gr TSX offers a flat shooting, high velocity projectile that offers excellent soft tissue terminal performance and good penetration.
When TSX's when fired through auto windshields, the jacket "petals" collapse against the nose, fold back against the core, or the "petals" are torn off; this results in a caliber size projectile configured a lot like a full wadcutter, leading to deep penetration whether shooting light or heavy TSX projectiles:
Barnes 53 gr TSX BG/auto window & Barnes 70 gr TSX BG/auto window fired from 16" 1/7 barrel at 10 feet:
As illustrated above, the lighter TSX's expand more in soft tissue and are no different when fired through auto glass than the heavier 70 gr TSX.
Thus for the vast majority of CONUS LE/personal defense use at typical ranges of under 100 yds, the 55 gr TSX offer the most versatility. For environments were longer range engagements beyond 300 meters may be necessary, the heavier 70 gr TSX is superior due to better BC and less wind drift (the 70 gr has a BC of .314, while the 55 gr has a .209 BC).
