The JSB Exact Jumbo Heavy has a good following of shooters.
At 18.13gr and with a head size of 5.52 the JSB Exact Jumbo Heavy in .22 calibre is a popular pellet with many who use PCPs though this pellet also performs well in springers over 12Fpe. Presently the JSB Exact Jumbo Heavy is only available in 5.52 unlike the JSB Exact Jumbo that comes in 3 sizes.
Warning: To avoid possible severe injury, only use ammunition that exactly matches marking on your gun. Use only in firearms recommended for this type of cartridge. If firearm fails to fire, keep it pointed in a safe direction. Wait. Unload carefully, avoid exposure to the breech. Keep barrel free of any obstruction. Wear shooting glasses to protect eyes from flying particles. Wear proper hearing protection; repeated exposure to gunfire can damage hearing. Be sure of your backstop. Handle with care; cartridges may discharge if dropped or crushed.