From what I remember 15+ years ago, Krieger cryoed their barrel blanks before their machining operations for one purpose, to improve the tool life in deep hole drilling, reaming, and cutting the rifling.
And yet several years ago Krieger quit cryo altogether because they finally admitted it did nothing to add to the process.
Good info from a poster that knows what he's talking about. Thanks very much for the post!There is so much misinformation on the internet about the Cryogenic treatment of barrels.
- Cryogenic processing of rifle barrels has not went away.
- All barrel steel has some amount of residual stress in it from the steel mill. How your barrel maker deals with this residual stress within the manufacturing process will determine the quality of the barrel.
I have a lot actual hands on experience with deep cryogenic treatment of barrels and stress relieving of 416 stainless. A proper deep cryogenic treatment cycle will improve a 416 stainless barrel regardless of the manufacturing process.
The cryogenic process like all other thermal operations is best performed on a cylindrical blank prior to contouring regardless of the rifling process. Cryogenic processing should be conducted prior to contouring and final lapping.
If a finished barrel is cryo treated the interior dimensions will shrink. The amount of shrinkage will vary based on a few factors.
- The amount of any remaining residual stresses in the barrel at the time of cryo
These small dimensional changes are the reason that high end race engine shops normally perform the cryogenic processing prior to final machining on engine parts.
Cryo alone will not fully stress relieve a barrel.... it takes heat and then cryo
Think of it this way.... a NOS system will greatly enhance the performance of your hot rod but you can't run it on NOS alone.
The process is more than just dipping a barrel into liquid nitrogen... That's Bad
Stress relieving barrel material is like old people sex... It needs to happen slow and easy.
The deep cryogenic process slowly ramps the material down from ambient to -300F or colder over several hours. The temperature is held at -300F or colder for 10-24 hours to allow the material to be thoroughly soaked to complete the transition of austenite to martensite. After the soak the temperature is allowed to slowly return to ambient and this warming up process may take 24 or more hours. The last step is to temper any newly formed martensite and that is done by raising the temperature of the material and soaking it at +300F for 1-3 cycles. This is a general idea of the process. Each material and processor will have their own specific recipe.
Yes it's a lot of extra work to manufacture a cryogenic treated barrel but it's worth it.
Good info, thanks manThere is so much misinformation on the internet about the Cryogenic treatment of barrels.
- Cryogenic processing of rifle barrels has not went away.
- All barrel steel has some amount of residual stress in it from the steel mill. How your barrel maker deals with this residual stress within the manufacturing process will determine the quality of the barrel.
I have a lot actual hands on experience with deep cryogenic treatment of barrels and stress relieving of 416 stainless. A proper deep cryogenic treatment cycle will improve a 416 stainless barrel regardless of the manufacturing process.
The cryogenic process like all other thermal operations is best performed on a cylindrical blank prior to contouring regardless of the rifling process. Cryogenic processing should be conducted prior to contouring and final lapping.
If a finished barrel is cryo treated the interior dimensions will shrink. The amount of shrinkage will vary based on a few factors.
- The amount of any remaining residual stresses in the barrel at the time of cryo
These small dimensional changes are the reason that high end race engine shops normally perform the cryogenic processing prior to final machining on engine parts.
Cryo alone will not fully stress relieve a barrel.... it takes heat and then cryo
Think of it this way.... a NOS system will greatly enhance the performance of your hot rod but you can't run it on NOS alone.
The process is more than just dipping a barrel into liquid nitrogen... That's Bad
Stress relieving barrel material is like old people sex... It needs to happen slow and easy.
The deep cryogenic process slowly ramps the material down from ambient to -300F or colder over several hours. The temperature is held at -300F or colder for 10-24 hours to allow the material to be thoroughly soaked to complete the transition of austenite to martensite. After the soak the temperature is allowed to slowly return to ambient and this warming up process may take 24 or more hours. The last step is to temper any newly formed martensite and that is done by raising the temperature of the material and soaking it at +300F for 1-3 cycles. This is a general idea of the process. Each material and processor will have their own specific recipe.
Yes it's a lot of extra work to manufacture a cryogenic treated barrel but it's worth it.
Just speaking generally but most cut bbls rely on the steel mill for stress relief as opposed to having that ability in-house. Not saying one is better than the other but I prefer small batches and better control of the process vs huge batches done at a mill. But trhe subject is cryo, which is a step further and has a somewhat different effect than heat stress relieving..and a different purpose. Cryo does not replace heat stress relieving.
Is there some vibratory action going on to help release the air bubbles?
