Spare yourself a whole lot of confusion by simply making any new combustion cannon a simple 1:1 ratio...
Some will argue that <b>0.8:1</b> is the best, others will argue that <b>0.7:1</b> is. - Some will even go so far as to say that a <b>1.5:1</b> ratio is the best.
You'll get good performance and a nice loud bang, from a 1:1 ratio. To figure <b>ANY</b> chamber size out, you must first figure out the barrels' volume.
This is accomplished by
1.)Dividing the <b>I.D.</b> (<b>I</b>nside <b>D</b>iameter) by 2
<center>2.445 / 2 = <b>1.225</b></center>
2.)Multiply this answer by itself
<center><b>1.2225</b> x <b>1.2225</b> = <b>1.49450625</b></center>
3.)Multiply <b>that</b> answer by "pi"
<center><b>1.49450625</b> x 3.14159 = <b>4.6951258899375</b></center>
This is how many cubic inches of volume you will have (per inch length) of barrel.
Round the number off to 2 or 3 digits past the decimal point:
And muliply that number by your intended barrel length:
<center><b>4.695 x 36" = 169.02</b></center>
With a <b>169</b> cubic inch barrel, simply do the same math for the chamber diameter, until you get to step # 3.
Then take your barrel volume of 169 and divide it by that number.