These springs are for recreational or competition shooting only and should not be installed in any rifle used for defense or duty applications or any AR-10 type rifle. The can be used with other calibers from the AR-15 platform, but reliability will be reduced with hard, low-sensitivity primers such as those found in NATO-spec and various foreign-manufactured ammunitions.
For full auto, duty, or large frame AR's, the JP Enterprises Enhanced Ignition Reliability Trigger Spring Kit would be the recommended springs to use.
https://www.opticsplanet.com/jp-enterprises-enhanced-ignition-trigger-spring-kit.html
These springs are for recreational or competition shooting only and should not be installed in any rifle used for defense or duty applications or any AR-10 type rifle. For full auto, duty, or large frame AR's, the JP Enterprises Enhanced Ignition Reliability Trigger Spring Kit would be the recommended springs to use.
https://www.opticsplanet.com/jp-enterprises-enhanced-ignition-trigger-spring-kit.html
Changing one can make a slight difference, but it would be best to change all three to get the actual effect. If you're worried about reliability, you could choose to go with the JP Enterprises Enhanced Ignition Reliability Trigger Spring Kit.
https://www.opticsplanet.com/jp-enterprises-enhanced-ignition-trigger-spring-kit.html
The JP springs are made of steel.