FX Impact M4 PCP Air Rifle FX Smooth Twist X Superior (STX) barrel system Interchangeable calibers and barrel liners (sold separately) Power Block Externally adjustable AMP MKII (Adjustable Match Precision) regulators Externally adjustable hammer spring tension with macro and micro adjustments Externally adjustable valve control Quick Tune System for virtually tool-free adjustments 250 BAR (3,625 PSI) max. fill pressure Max regulator working pressure of 170 BAR Equipped with improved 75cc Power Plenum 750 - allowing for an even wider range of power adjustment .22 and .25 cal M4's feature Dual transfer ports - one optimized for pellets, one for slugs Male Quick Disconnect fitting Shroud is threaded 1/2x20 for moderator Forward mounted reversible sidelever cocking Picatinny/Weaver optics mounting rail with 30 MOA compensation rides on 11mm dovetail allowing further customization to meet every shooters need Picatinny accessory rails below cylinder and on each side of the forearm New Quick Set Trigger - Adjustable match trigger Wika dual pressure gauges: one for air cylinder pressure, one for regulator pressure.   Height adjustable rubber buttpad FX UG1 AR15 style grip AR15 style manual safety Redesigned Side Shot magazine capacity*: 34 rds. in .177, 28 rds. in .22, 25 rds. in .25, 23 rds. in .30 Maximum muzzle energy **: 35 FPE in .177  87 FPE in .22  100 FPE in .25  125 FPE in .30  Includes one side-shot magazine, FX moderator, and 3 year transferable warranty *  - Older Side Shot magazines are compatible with the M4.  ** - Max Energy achieved with FX Slug Power Kit installed. 600mm (23.62") Barrel, Standard Models: Available in .177, .22, .25 and .30 cal. Removable 480cc carbon fiber air cylinder Overall length of 34" Weight: 6.85 lbs. Shots per fill: 375 in .177, 270 in .22, 130 in .25 and 85 in .30 700mm (27.55") Barrel, Sniper Models: Available in .22, .25 and .30 cal. Removable 580cc carbon fiber air cylinder Overall length of 39" Weight: 7.15 lbs. Shots per fill: 330 in .22, 160 in .25 and 105 in .30 Tech Note: While the manual states the M4 models are capable of 300 BAR fill pressures, this is only achievable with aftermarket carbon fiber bottles. The current factory bottles from FX that are included on the rifles are rated for 250 BAR fill pressures and should not be filled over this pressure.