My 10-mm Tanfoglio 4.5-inch Witness is upgraded with an 20.5-lb net-force Wolff 18-lb Tanfoglio long-slide recoil spring (from a 14-lb factory spring), stainless-steel cone-fit guide-rod, and 2-mm brass shock buffer. I load it with Fiocchi 180-grains, 1250-f/s JHP or FMJ ball. The large-frame Witness has a heavy slide, but the CZ-75 design makes use of locking lugs, similar to John Browning's 1911 45-ACP and Hi-Power 9-mm pistols. The mating surface between the factory guide-rod base and pistol frame take a beating especially with no shock buffer in place as a cushion.
The 14-lb factory recoil spring is too soft to deal with near-Norma 10-mm loads, but with Henning Group parts and a stiffer Wolff recoil spring, this pistol can withstand 180-grains 1250-f/s loads for low-volume rounds range practice.
For higher volume shooting, I use my 40 S&W-version of the Tanfoglio Large Frame Witness. 40 S&W ammo loads are 1050-f/s Aguila or 1040-f/s LAX FMJ. The 40-S&W Tanfoglio is also upgraded with Henning Group cone-fit stainless-steel guide rod, Wolff 16-lb Tanfoglio Long-Slide recoil spring, and a 2-mm brass shock buffer. Total net force of recoil spring/shock buffer is 18.5 lbs.
The Henning Group brass shock buffer buffer has a usable life of ~200 to 250 10-mm rounds before needing replacement.
If using the shock buffer during carry--it's important to wear in the buffer with at least 50-rounds to test slide lock-back-after-the last-round.
If using the factory Witness setup, a lighter 10-mm load is ideal--such as those available from range shops or sporting goods stores. These loads include Sellier & Bellot 180-grains 1164-f/s FMJ, American Eagle, Remington, and Union Metallic Cartridge (UMC) 180-grains 1150-f/s FMJ. These lighter 10-mm loads are softer-recoiling, and much easier on the more fragile factory Tanfoglio large-frame Witness setup.
My box--stock 10-mm SIG P220 Elite 5-inch pistol is loaded with Underwood 220-grains, 1200-f/s hard-cast flat-nose or 200-grains, 1250-f/s FMJ ball.
The SIG has a simpler slide-to-frame lock up design (no locking lugs in either slide or frame), and has a captured recoil spring-on-guide rod with a 22-lb braided recoil spring. The stiff spring and simpler design allows the SIG 220 to fire full 10-mm Norma loads originally designed by Jeff Cooper for his cartridge.
The 10-mm Underwood are as close to the original 10-mm Norma loads as you'll find.
With regard to FMJ vs JHP for carry service, mission environment dictates ammo loads. If the environment is unknown--prepare for the worst-case scenario--threat-targets shooting from cover or concealment, wearing Level-3A body armor.
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