I believe the 453 American was initially released in .22LR and .17 Mach 2. In 2006 they released the .17HMR at a $30 additional cost.
You can occasionally see the Mach 2 chambered ones come up at auction but that chambering kinda became superfluous with the release of the HMR.
I have a 453 American in .17 HMR. It’s a tack driver but sometimes suffers from light strikes, even with an extra power DIP spring. Great for ground hogs out to about 130 yards. Beyond that you really start to lose energy.
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