Make sure to watch my Vimeo video for this Comparison Review as I go into a lot of detail about the similarities and difference with each of these CO2 Blowback Pellet Guns.
Here are some of the main Similarities when comparing the Sig Sauer P250 & P226 - Umarex PX4 Storm - Gamo P25 & MP9:
- All of these CO2 blowback pellet guns are made for each company in Japan (I am assuming from the same factory?) 
- All of the listed Pellet Airguns shoot .177 caliber pellets (Can be Alloy or Lead) 
- They all have double sided rotary stick magazines that hold 8 rounds on each end for a total of 16 shots per magazine. 
- All of the Airguns use 12 gram CO2. 
- All compared pellet guns have Blowback operation. 
- All of these pellet pistols have single and double action triggers except for the Gamo MP9 which is single action only and needs to be charged on the first shot. 
- They all have rifled barrels. 
Here is where we find some key differences between these CO2 Blowback Pellet Pistols:
The FPS Velocity for each Airgun:
- Gamo P-25 - 450 BPA Platinums. 
- Gamo MP9 - 450 BPA Platinums. 
- Umarex PX4 Storm - 380. 
- Sig Sauer P250 - 400 with 5.25 grain. 
- Sig Sauer P226 - 400 with 5.25 grain. 
The weight of Each Pellet Gun:
- Gamo P-25 - 1.7 pounds. 
- Gamo MP9 - 3 pounds. 
- Umarex PX4 Storm - 1.6 pounds. 
- Sig Sauer P250 - 1.45 pounds. 
- Sig Sauer P226 - 2.35 pounds. 
The Barrel Length for each Air Pistol:
- Gamo P-25 - 4.5 inches. 
- Gamo MP9 - 6.5 inches. 
- Umarex PX4 Storm - 4.5 inches. 
- Sig Sauer P250 - 4.75 inches. 
- Sig Sauer P226 - 4.75 inches. 
The Main Build Materials for each Pellet Pistol:
- Gamo P-25 - Metal slide with plastic frame. 
- Gamo MP9 - Plastic outer shell with lots of internal metal parts. 
- Umarex PX4 Storm - Metal slide with plastic frame. 
- Sig Sauer P250 - Metal slide with plastic frame. 
- Sig Sauer P226 - Metal slide and frame. 
Is the Ejection Port Cut Out?
- Gamo P-25 - Yes. 
- Gamo MP9 - No. 
- Umarex PX4 Storm - Yes. 
- Sig Sauer P250 - No. 
- Sig Sauer P226 - No. 
Is it a Replica of a Real Steel Gun?
- Gamo P-25 - No. 
- Gamo MP9 - Yes. 
- Umarex PX4 Storm - Yes. 
- Sig Sauer P250 - Yes. 
- Sig Sauer P226 - Yes. 
 
 