# Reply To: Zbroia Kozak 177 arrived today

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I took some measurements and did some calculations, and here is what I came up with:

Original spring is 1.6 inches long, has 0.043 inch wire diameter and 0.26 inch outer diameter.

I’ve used this calculator https://www.acxesspring.com/spring-calculator.html to calculate spring constant of 32 lb/in

In my 177 12 fpe set up original spring compressed 0.45 inches, which produces 14.4 pounds of energy to the hammer.

Back to the calculator with my smaller 0.037 wire same outer diameter and length spring will give me 16lb/in constant.

My second spring will be shorter 1.2 inch spring with 9 coils and 0.32 inch outer diameter. end cap measure 0.388 inches and has plenty of space to support this second spring.

According to calculator second spring constant will be 13.1 lb/in. Combined constant will be 29.1 lb/in of two springs and I will need to adjust them to get 12fpe power output (about .5 inches compression). Now will try to make these springs.

this is original cap inside end cap adjuster

spring guide back when cocked.