So I started upgrading the Classic Army CA25 AEG that I got from  This is by far, my favorite rifle of all rifles in the world of real steel, so I'm actually ashamed of myself that it's taken me this long to acquire one, when I've been playing for years and have spent an shameful amount of money on other guns and projects.  Long story short, I am going to a masterpiece in the form of a long-range, semi-automatic sniper system in honor of the CA25's real steel counterpart.

To start, decided to work on the accuracy stuff first, since accuracy is much more important than how hard/far the gun shoots.  What difference does it make if your gun shoots 540 FPS if you can't hit the proverbial broad side of a barn?  First thing I did was swap out the stock inner barrel and replace it with a custom, 6.01mm diameter, 534mm length EdGI tightbore barrel cut to my specs by Ben Noji of PolarStar Airsoft fame. I chose the 534mm length because of the larger-than-normal cylinder volume that the CA25 uses. I measured the length and radius (diameter divided by two) of the CA25 using Mitutoyo Digimatic calipers to the best of my limited abilities.  My goal is to optimize the length of the inner barrel, which affects the volume inside the barrel so that there is maximum energy transfer to the BB upon firing the AEG.  I'm no physicist or anything, but I have figured out who to talk to about things like this, and that's basically what the purpose of this procedure is for. 

So first, I had to take some measurements of the CA25's cylinder. 

CA25 Cylinder Height
Airsoft Guns, Classic Army, CA25, SR25, M110 SASS,Airsoft AEG, automatic electric gun,AEG, CA, SASS, Eugene Stoner Rifle,pyramyd air, airsoft obsessed
I forgot to get a picture, but I also reduced the cylinder height shown above by the amount that the cylinder head is inserted into the cylinder.  I measured the cylinder head with the calipers as well.

CA25 Cylinder Diameter (which I divided by 2 to get the radius)
Airsoft Guns, Classic Army, CA25, SR25, M110 SASS,Airsoft AEG, automatic electric gun,AEG, CA, SASS, Eugene Stoner Rifle,pyramyd air, airsoft obsessed

As stated in the super sweet title of the blog entry, my objective is to figure out what an optimal length for my inner barrel would be, based on a few pieces of given information and criteria.  I know I wanted a 6.01mm diameter barrel and the cylinder volume is set in stone, so that only left the height/length of the inner barrel TBD.  Through the use of my mad algebra skillz and the superb ability to solve for "X," I figured out based on the numbers I established and listed below, I was able to calculate that I needed somewhere around a 534mm-length inner barrel, which is actually slightly longer than the stock inner barrel that Classic Army put in the gun.  Here are the numbers:

Height (mm) Diameter (mm) Radius (mm) Pi Volume
Barrel Volume 534 6.01 3.005 3.14 15,141.18mm^3
Cylinder Volume 74.26 23.81 11.905 3.14 33,047.86mm^3
C to B Ratio--> 2.18

Cylinder Head Height 7.47 mm

Cylinder Height 81.73 mm

Net Height 74.26 mm

Cylinder Diameter 23.81 mm

Cylinder Radius       11.905 mm

Pi        3.14

So, long-story short, that's how I was able to calculate a relatively optimal length for my CA25 Airsoft DMR project. Next, I'll discuss what I'm experimenting with on the hop-up. 


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